Jesus Giraldo - Academia.edu (original) (raw)
Papers by Jesus Giraldo
British Journal of Pharmacology, 1999
Purinergic and adrenergic components of the contractile response to electrical field stimulation ... more Purinergic and adrenergic components of the contractile response to electrical field stimulation (EFS) have been investigated in epididymal and prostatic portions of Wystar Kyoto (WKY) and spontaneously hypertensive rat (SHR) vas deferens.In both halves of SHR and WKY vas deferens, EFS (40 V, 0.5 ms for 30 s, 0.5–32 Hz) evoked frequency-related contractions. The neurogenic responses were biphasic, consisting of a rapid non-adrenergic response, dominant in the prostatic portion, followed by a slow tonic adrenergic component, dominant in the epididymal half.Phasic and tonic components of the frequency-response curves evoked by EFS were significantly higher in the epididymal but not in the prostatic portion of vas deferens from SHR compared to WKY rats.The α1-adrenoceptor antagonist prazosin (0.1 μM) was more effective against both components of the contractile response in the epididymal end of SHR than in WKY rats.Inhibition by α,β-methylene adenosine 5′-triphosphate (α,β-meATP 3 and 30 μM) was higher in both components of the contractile responses in WKY preparations than in SHR.Combined α1-adrenoceptor and P2x-purinoceptor antagonism virtually abolished the EFS-evoked contractile response in both strains. The degree of inhibition by prazosin (0.1 μM) after P2x-purinoceptor blockade was higher in SHR than in WKY rats.These results demonstrate a modification in the purinergic and noradrenergic contribution to neurogenic responses in SHR and WKY animals besides a co-participation of ATP and noradrenaline in both contractile components of the response to EFS.Purinergic and adrenergic components of the contractile response to electrical field stimulation (EFS) have been investigated in epididymal and prostatic portions of Wystar Kyoto (WKY) and spontaneously hypertensive rat (SHR) vas deferens.In both halves of SHR and WKY vas deferens, EFS (40 V, 0.5 ms for 30 s, 0.5–32 Hz) evoked frequency-related contractions. The neurogenic responses were biphasic, consisting of a rapid non-adrenergic response, dominant in the prostatic portion, followed by a slow tonic adrenergic component, dominant in the epididymal half.Phasic and tonic components of the frequency-response curves evoked by EFS were significantly higher in the epididymal but not in the prostatic portion of vas deferens from SHR compared to WKY rats.The α1-adrenoceptor antagonist prazosin (0.1 μM) was more effective against both components of the contractile response in the epididymal end of SHR than in WKY rats.Inhibition by α,β-methylene adenosine 5′-triphosphate (α,β-meATP 3 and 30 μM) was higher in both components of the contractile responses in WKY preparations than in SHR.Combined α1-adrenoceptor and P2x-purinoceptor antagonism virtually abolished the EFS-evoked contractile response in both strains. The degree of inhibition by prazosin (0.1 μM) after P2x-purinoceptor blockade was higher in SHR than in WKY rats.These results demonstrate a modification in the purinergic and noradrenergic contribution to neurogenic responses in SHR and WKY animals besides a co-participation of ATP and noradrenaline in both contractile components of the response to EFS.British Journal of Pharmacology (1999) 128, 873–880; doi:10.1038/sj.bjp.0702845
American Journal of Physiology-heart and Circulatory Physiology, 2007
Transient focal cerebral ischemia in the rat alters vessel properties, and spontaneously hyperten... more Transient focal cerebral ischemia in the rat alters vessel properties, and spontaneously hypertensive rats (SHR) show a poorer outcome after ischemia. Here we examined the role of hypertension on vessel properties after ischemia/reperfusion. The right middle cerebral artery (MCA) was occluded (90 min) and reperfused (24 h) in SHR (n=12) and
![Research paper thumbnail of Use of the operational model of agonism and [3H]prazosin binding to assess altered responsiveness of α1-adrenoceptors in the vas deferens of spontaneously hypertensive rat](https://a.academia-assets.com/images/blank-paper.jpg)
](Naunyn-schmiedebergs Archives of Pharmacology, 1997
Changes in functional responsiveness to α1-adrenoceptor activation with noradrenaline and in [3H]... more Changes in functional responsiveness to α1-adrenoceptor activation with noradrenaline and in [3H]prazosin binding in the epididymal portion of vas deferens from normotensive Wistar Kyoto (WKY) and spontaneously hypertensive rats (SHR) were investigated. The operational model fitting and the nested hyperbolic method were used to analyze the effects of irreversible receptor alkylation by phenoxybenzamine (0.1 μM) on the α1-adrenoceptor mediated contractile responses to noradrenaline of vasa deferentia from SHR and WKY rats. Saturation isotherms for [3H]prazosin revealed a significant increase (P < 0.05) in the Bmax in SHR vas deferens (145 ± 19 fmol/mg protein) compared with vas deferens from normotensive controls (75 ± 12 fmol/mg protein) without changes in the KD. No differences in the proportion of high and low affinity binding sites for WB-4101 and 5-methylurapidil were observed. The maximum contractile response, α, (P < 0.001) and the pEC50 (P < 0.05) values for noradrenaline were greater for SHR than for WKY rat tissues. The apparent affinity (pKA) determined by the nested hyperbolic method and by the operational model of agonism was found to be similar in the two strains. In agreement with relative pEC50, the efficacy (τ) value for SHR was greater than for WKY rats. However, the difference in the τ estimates did not reach statistical significance. In summary, in the epididymal portion of SHR vas deferens, the increased maximum contractile response to noradrenaline is due to an increase of Em. Taken together, the τ values and the results from binding experiments lead to the assumption that the transducer constant K E must be greater in SHR than in WKY rats, suggesting a deterioration in the transduction of the stimulus provided by the agonist in hypertensive animals.
Autonomic and Autacoid Pharmacology, 2005
1 Our aim was to study the role of nitric oxide (NO) and arachidonic acid pathways in the α1-adre... more 1 Our aim was to study the role of nitric oxide (NO) and arachidonic acid pathways in the α1-adrenoceptor-mediated vasoconstriction in mesenteric resistance arteries from 3–4 and 22 to 23-month-old Sprague-Dawley rats.2 The expression of NO synthase (NOS), cyclooxygenase (COX) isoforms, soluble guanylate cyclase, superoxide dismutase and the NAD(P)H oxidase subunits p22phox and p47phox were determined.3 The NG-nitro-l-arginine methyl ester, a non-selective NOS inhibitor, shifted to the left but indomethacin and NS 398, non-selective and selective COX-2 inhibitors, shifted to the right the concentration-response curve for the vasoconstriction by phenylephrine in both age groups.4 Ageing up-regulated endothelial NOS and p22phox expression but did not modify COX, soluble guanylate cyclase, superoxide dismutase and p47phox expression.5 These data suggest that the observed enhancement of eNOS protein expression could constitute a compensatory mechanism to counter-regulate a chronic loss of NO possibly through increased superoxide anion production from NAD(P)H oxidase induced by age.
Naunyn-schmiedebergs Archives of Pharmacology, 2002
The main objective of this study has been to analyse the electrophysiological differences in the ... more The main objective of this study has been to analyse the electrophysiological differences in the prostatic portion of vas deferens between spontaneously hypertensive (SHR) and Wistar Kyoto rats (WKY). Resting membrane potentials (RMP) recorded in SHR (–63.8±0.3 mV) and WKY (–68.1±0.3 mV) were significantly different. Bath applications of suramin (30 µM), α,β-methylene adenosine 5'-triphosphate (α,β-meATP; 30 µM) or prazosin (0.1 µM) did not modify the control values of RMP. In control conditions, spontaneous excitatory junction potentials (SEJPs) were recorded in preparations from both groups of animals. SEJPs registered in SHR were greater than those in WKY in amplitude (7.0±0.4 mV vs. 2.6±0.1 mV) and frequency (0.25±0.02 Hz vs. 0.14±0.01 Hz). SEJP amplitude was abolished by bath applications of suramin (30 µM) or α,β-meATP (30 µM). However, tetrodotoxin (TTX; 1 µM) and prazosin (0.1 µM) had no effect on this spontaneous activity. Electrical-field stimulation (EFS; 0.1 ms, 20 V, 0.2 Hz) induced an enhanced excitatory junction potential (EJP) in SHR but not in WKY (16.0±0.6 mV vs. 12.2±0.5 mV) which was abolished by TTX (1 µM), suramin (30 µM) and α,β-meATP (30 µM). The degree of inhibition of both SEJP and EJP produced by α,β-meATP (0.3–30 µM) was greater in SHR than in WKY. This study demonstrates an altered purinergic contribution to the co-transmission process in the prostatic portion of vas deferens from SHR.
Transient focal cerebral ischemia in the rat alters vessel properties, and spontaneously hyperten... more Transient focal cerebral ischemia in the rat alters vessel properties, and spontaneously hypertensive rats (SHR) show a poorer outcome after ischemia. Here we examined the role of hypertension on vessel properties after ischemia/reperfusion. The right middle cerebral artery (MCA) was occluded (90 min) and reperfused (24 h) in SHR (n=12) and
Pharmacology & Therapeutics, 2002
Modeling the shape of concentration-effect curves is of prime importance in pharmacology. Geometr... more Modeling the shape of concentration-effect curves is of prime importance in pharmacology. Geometric descriptors characterizing these curves (the upper and lower asymptotes, the mid-point, the mid-point slope, and the point of inflection) are used for drug comparison or for assessing the change in agonist function after a system modification. The symmetry or asymmetry around the mid-point of a concentration-effect curve is a fundamental property that, regretfully, is often overlooked because, generally, models yielding exclusively symmetric curves are used. In the present review, empirical and mechanistic models are examined in their ability to fit experimental data. The geometric parameters of a survey of empirical models, the Hill equation, a logistic variant that we call the modified Hill equation, the Richards function, and the Gompertz model are determined. To analyze the relationship between asymmetry and mechanism, some examples from the ionic channel field, in an increasing degree of complexity, are used. It is shown that asymmetry arises from ionic channels with multiple binding sites that are partly occupied. The operational model of agonism is discussed both in its empirical general formulation and including the signal transduction mechanisms through G-protein-coupled receptors. It is shown that asymmetry results from systems where receptor distribution is allowed. Developed mathematical models are compared for describing experimental data on α-adrenoceptors. The existence or not of a relationship between the shape of the curves and receptor reserve is discussed.
Journal of Pharmacology and Experimental Therapeutics, 2005
List of non-standard abreviation: 8-Br-cGMP, 8-Bromoguanosine 3',5'-cyclic monophosphate IL-1ß, i... more List of non-standard abreviation: 8-Br-cGMP, 8-Bromoguanosine 3',5'-cyclic monophosphate IL-1ß, interleukin-1ß eNOS, endothelial nitric oxide synthase iNOS, inducible nitric oxide synthase L-NAME, N w -Nitro-L -Arginine Methyl Ester MRA, mesenteric resistance arteries NO, nitric oxide sGC, soluble guanylate cyclase PEG-SOD, polyethylene glycol superoxide dismutase JPET #88435 3 SNP, sodium nitroprusside TNF-α, tumor necrosis factor-α 1400W, N-3-aminomethylbenzylacetamidine Section Assignment: Cardiovascular JPET #88435 4 Abstract The present study was designed to analyze the effect of long term incubation with interleukin 1ß (IL-1ß) on endothelium-dependent relaxation in rat mesenteric resistance arteries. Vessels were incubated in culture medium with or without IL-1ß (10 ng/ml, 14 h). Changes in lumen diameter were recorded in a pressure myograph. Protein expression, nitrite and superoxide anion (O 2 .-) production were evaluated by either Western blot or immunofluorescence, Griess reaction and ethidium fluorescence, respectively. IL-1ß impaired acetylcholine (ACh) and sodium nitroprusside (SNP) vasodilation and increased nitrite and O 2 .production and inducible nitric oxide synthase (iNOS), xanthine oxidase and p22 phox expression. However, neither endothelial NOS nor soluble guanylate cyclase protein expression were affected by IL-1ß treatment. Polyethylene glycol superoxide dismutase partially reversed the impairment of ACh relaxation and abolished the O 2 .production observed in IL-1ß treated arteries. The impairment of ACh relaxation induced by IL-1ß was also partially reversed by the xanthine oxidase inhibitor, allopurinol (1 mM), but not by either the NADPH oxidase inhibitor, apocynine (0.3 mM) or the iNOS inhibitor, 1400W (1 µM). However, all these inhibitors improved the impaired SNP response. The results of the present study demonstrate that long-term incubation with IL-1ß induces an impairment of the nitric mediated relaxation in mesenteric resistance arteries through the production of O 2 .mainly from xanthine oxidase. JPET #88435 5
British Journal of Pharmacology, 1997
We have studied the α1-adrenoceptor-mediated responses in intact tail artery rings from 3–4 and 2... more We have studied the α1-adrenoceptor-mediated responses in intact tail artery rings from 3–4 and 20–22 months old Sprague-Dawley rats, focusing on possible endothelial alterations. The influence of nitric oxide released by the endothelium, the number of α1-adrenoceptors and the functional receptor reserve were evaluated to determine their contribution to the contractile response mediated by this receptor. The state of the endothelial layer was assessed by confocal microscopy.Noradrenaline (1 nM–100 μM) induced concentration-dependent vasoconstriction. The maximum contractions to noradrenaline (P<0.05) and to 75 mM KCl (P<0.01) were higher in young than in old animals.The density (Bmax) of α1-adrenoceptors and the dissociation constant (KD) obtained in [3H]-prazosin binding experiments were unchanged by age.The apparent affinity (pKA) and the percentage of functional receptors (qx100) remaining after phenoxybenzamine (0.03 μM) were similar in both age groups.After partial α1-adrenoceptor inactivation with phenoxybenzamine, NG-nitro-L-arginine methylester (30 μM) significantly potentiated the E/[A] curve to noradrenaline in young rats. However, only responses to 0.1 to 1 μM noradrenaline were significantly potentiated in old animals. In addition, 94% of the vessels from young, but only 52% from old rats were relaxed by 80–100% of the noradrenaline (0.03 μM) contraction, with 1 μM acetylcholine.No modifications in the area (μm2) or in the number of endothelial nuclei (per mm2) were observed between age groups. An elongation of the nuclei of endothelial cells was observed in the old animals.These data suggest that the noradrenaline-induced contraction is decreased in old rats probably due to differences in either the contractile machinery or postreceptor mechanisms. These alterations may be accompanied by an impairment of the release or production of NO from endothelial cells.We have studied the α1-adrenoceptor-mediated responses in intact tail artery rings from 3–4 and 20–22 months old Sprague-Dawley rats, focusing on possible endothelial alterations. The influence of nitric oxide released by the endothelium, the number of α1-adrenoceptors and the functional receptor reserve were evaluated to determine their contribution to the contractile response mediated by this receptor. The state of the endothelial layer was assessed by confocal microscopy.Noradrenaline (1 nM–100 μM) induced concentration-dependent vasoconstriction. The maximum contractions to noradrenaline (P<0.05) and to 75 mM KCl (P<0.01) were higher in young than in old animals.The density (Bmax) of α1-adrenoceptors and the dissociation constant (KD) obtained in [3H]-prazosin binding experiments were unchanged by age.The apparent affinity (pKA) and the percentage of functional receptors (qx100) remaining after phenoxybenzamine (0.03 μM) were similar in both age groups.After partial α1-adrenoceptor inactivation with phenoxybenzamine, NG-nitro-L-arginine methylester (30 μM) significantly potentiated the E/[A] curve to noradrenaline in young rats. However, only responses to 0.1 to 1 μM noradrenaline were significantly potentiated in old animals. In addition, 94% of the vessels from young, but only 52% from old rats were relaxed by 80–100% of the noradrenaline (0.03 μM) contraction, with 1 μM acetylcholine.No modifications in the area (μm2) or in the number of endothelial nuclei (per mm2) were observed between age groups. An elongation of the nuclei of endothelial cells was observed in the old animals.These data suggest that the noradrenaline-induced contraction is decreased in old rats probably due to differences in either the contractile machinery or postreceptor mechanisms. These alterations may be accompanied by an impairment of the release or production of NO from endothelial cells.
British Journal of Pharmacology, 1997
The influence of l-NG-nitro-arginine (l-NOARG, 30 μm) on contractile responses to exogenous norad... more The influence of l-NG-nitro-arginine (l-NOARG, 30 μm) on contractile responses to exogenous noradrenaline was studied in the rat anococcygeus muscle.Noradrenaline (0.1–100 μm) contracted the muscle in a concentration-dependent manner. l-NOARG (30 μm) had no effect on noradrenaline responses.Phenoxybenzamine (Pbz 0.1 μm) depressed by 46% (P<0.001) the maximum response and shifted to the right (P<0.001) the E/[A] curve to noradrenaline (pEC50 control: 6.92±0.09; pEC50 Pbz: 5.30±0.10; n=20).The nested hyperbolic null method of analysing noradrenaline responses after phenoxybenzamine showed that only 0.61% of the receptors need to be occupied to elicit 50% of the maximum response, indicating a very high functional receptor reserve.Contractile responses to noradrenaline after partial α1-adrenoceptor alkylation with phenoxybenzamine (0.1 μm) were clearly enhanced by l-NOARG.The potentiating effect of l-NOARG on noradrenaline responses after phenoxybenzamine was reversed by (100 μm) l-arginine but not by (100 μm) d-arginine.These results indicate that spontaneous release of NO by nitrergic nerves can influence the α1-adrenoceptor-mediated response to exogenous noradrenaline.The influence of l-NG-nitro-arginine (l-NOARG, 30 μm) on contractile responses to exogenous noradrenaline was studied in the rat anococcygeus muscle.Noradrenaline (0.1–100 μm) contracted the muscle in a concentration-dependent manner. l-NOARG (30 μm) had no effect on noradrenaline responses.Phenoxybenzamine (Pbz 0.1 μm) depressed by 46% (P<0.001) the maximum response and shifted to the right (P<0.001) the E/[A] curve to noradrenaline (pEC50 control: 6.92±0.09; pEC50 Pbz: 5.30±0.10; n=20).The nested hyperbolic null method of analysing noradrenaline responses after phenoxybenzamine showed that only 0.61% of the receptors need to be occupied to elicit 50% of the maximum response, indicating a very high functional receptor reserve.Contractile responses to noradrenaline after partial α1-adrenoceptor alkylation with phenoxybenzamine (0.1 μm) were clearly enhanced by l-NOARG.The potentiating effect of l-NOARG on noradrenaline responses after phenoxybenzamine was reversed by (100 μm) l-arginine but not by (100 μm) d-arginine.These results indicate that spontaneous release of NO by nitrergic nerves can influence the α1-adrenoceptor-mediated response to exogenous noradrenaline.British Journal of Pharmacology (1997) 120, 1035–1038; doi:10.1038/sj.bjp.0701005
Journal of Autonomic Pharmacology, 1999
1 The present study focuses on the role of endothelium on a 1 -adrenoceptor-mediated vasoconstric... more 1 The present study focuses on the role of endothelium on a 1 -adrenoceptor-mediated vasoconstriction in aorta from Wistar Kyoto (WKY) and spontaneously hypertensive rats (SHR). To define and quantify changes in the parameters governing agonism at a 1 -adrenoceptor by hypertension and/or endothelium, the operational model of analysis was used. 2 In either endothelium intact or denuded aorta, the sensitivity (P < 0.001) and the maximum contraction (P < 0.05) to phenylephrine were smaller in SHR than in WKY. 3 However, in each strain of rats, removal of endothelium increased the sensitivity (P < 0.001) to phenylephrine but reduced (P < 0.05) KCl-evoked vasoconstriction, suggesting a modulation of these responses by the endothelium. The observed differences in sensitivity and maximum contraction are interpreted in terms of the operational parameters: E m , the maximum possible effect; pK A , the agonist affinity; a, the agonist efficacy and n, the slope for the function relating receptor occupancy to pharmacological effect. The estimated parameters reflected differences, between strains, in the signal transduction processes linked to a 1 -adrenoceptor stimulation ascribed to the presence of the endothelium. 4 N G -nitro-l-arginine methyl ester (L-NAME), enhanced to a similar extend in both rat strains the sensitivity (P < 0.001) and the maximum contraction to phenylephrine. Indomethacin reduced the maximum contraction to phenylephrine by 56.85% in SHR and by 11.80% in WKY suggesting that contracting prostanoids play a more major role in this response in SHR than in WKY. Nevertheless, these inhibitors were without effect on denuded vessels from both strains suggesting that NO and cyclooxygenase products from the media or the adventitia do not play a role on the phenylephrinemediated responses. 5 The studied endothelial factors partially explain the observed differences in modulation of a 1adrenoceptor responses by the endothelium but suggest the participation of other compounds released by the endothelium.
British Journal of Pharmacology, 2003
There is a long-known hyper-responsiveness of vascular adrenergic transmission in the spontaneous... more There is a long-known hyper-responsiveness of vascular adrenergic transmission in the spontaneously hypertensive rat (SHR) that is uncovered specifically in the presence of cocaine and attributed to blockade of the neuronal monoamine transporter. We have now used the rat anococcygeus muscle to investigate whether this phenomenon is generic to sympathetic transmission to smooth muscle rather than a purely vascular phenomenon. We sought the origin of the effect by successively blocking the buffering effects of the neuronal monoamine transporter, prejunctional α2-adrenoceptors and NO from nitrergic nerves with desipramine (0.1 μM), rauwolscine (0.01 μM) and L-NG-nitro-arginine (100 μM).In the presence of desipramine, contractile responses to electrical field stimulation but not to noradrenaline (1 nM–100 μM) were greater in SHR than in Wistar–Kyoto (WKY). Neither inhibition of prejunctional α2-adrenoceptors nor the blockade of neuronal nitric oxide synthase (nNOS) accounted for the differential enhancement of response in SHR. The enhanced effectiveness of motor neurotransmission in SHR becomes most apparent when all known major buffering mechanisms are removed.When nitrergic responses were isolated pharmacologically (phentolamine 1 μM and guanethidine 30 μM; tone raised with carbachol 50 μM), they were not different between SHR and WKY.Western blots showed that both nNOS and tyrosine hydroxylase are expressed to a similar extent in anococcygeus muscle from SHR and WKY, suggesting similar adrenergic and nitrergic innervations in the two strains. This suggests that enhanced motor transmission is due to increased transmitter release per varicosity rather than there being normal transmission from a greater number of sites.We conclude that there is a generic enhancement of sympathetic transmission in SHR rather than this being a vascular phenomenon.There is a long-known hyper-responsiveness of vascular adrenergic transmission in the spontaneously hypertensive rat (SHR) that is uncovered specifically in the presence of cocaine and attributed to blockade of the neuronal monoamine transporter. We have now used the rat anococcygeus muscle to investigate whether this phenomenon is generic to sympathetic transmission to smooth muscle rather than a purely vascular phenomenon. We sought the origin of the effect by successively blocking the buffering effects of the neuronal monoamine transporter, prejunctional α2-adrenoceptors and NO from nitrergic nerves with desipramine (0.1 μM), rauwolscine (0.01 μM) and L-NG-nitro-arginine (100 μM).In the presence of desipramine, contractile responses to electrical field stimulation but not to noradrenaline (1 nM–100 μM) were greater in SHR than in Wistar–Kyoto (WKY). Neither inhibition of prejunctional α2-adrenoceptors nor the blockade of neuronal nitric oxide synthase (nNOS) accounted for the differential enhancement of response in SHR. The enhanced effectiveness of motor neurotransmission in SHR becomes most apparent when all known major buffering mechanisms are removed.When nitrergic responses were isolated pharmacologically (phentolamine 1 μM and guanethidine 30 μM; tone raised with carbachol 50 μM), they were not different between SHR and WKY.Western blots showed that both nNOS and tyrosine hydroxylase are expressed to a similar extent in anococcygeus muscle from SHR and WKY, suggesting similar adrenergic and nitrergic innervations in the two strains. This suggests that enhanced motor transmission is due to increased transmitter release per varicosity rather than there being normal transmission from a greater number of sites.We conclude that there is a generic enhancement of sympathetic transmission in SHR rather than this being a vascular phenomenon.British Journal of Pharmacology (2003) 140, 773–779. doi:10.1038/sj.bjp.0705480
British Journal of Pharmacology, 1999
Purinergic and adrenergic components of the contractile response to electrical field stimulation ... more Purinergic and adrenergic components of the contractile response to electrical field stimulation (EFS) have been investigated in epididymal and prostatic portions of Wystar Kyoto (WKY) and spontaneously hypertensive rat (SHR) vas deferens.In both halves of SHR and WKY vas deferens, EFS (40 V, 0.5 ms for 30 s, 0.5–32 Hz) evoked frequency-related contractions. The neurogenic responses were biphasic, consisting of a rapid non-adrenergic response, dominant in the prostatic portion, followed by a slow tonic adrenergic component, dominant in the epididymal half.Phasic and tonic components of the frequency-response curves evoked by EFS were significantly higher in the epididymal but not in the prostatic portion of vas deferens from SHR compared to WKY rats.The α1-adrenoceptor antagonist prazosin (0.1 μM) was more effective against both components of the contractile response in the epididymal end of SHR than in WKY rats.Inhibition by α,β-methylene adenosine 5′-triphosphate (α,β-meATP 3 and 30 μM) was higher in both components of the contractile responses in WKY preparations than in SHR.Combined α1-adrenoceptor and P2x-purinoceptor antagonism virtually abolished the EFS-evoked contractile response in both strains. The degree of inhibition by prazosin (0.1 μM) after P2x-purinoceptor blockade was higher in SHR than in WKY rats.These results demonstrate a modification in the purinergic and noradrenergic contribution to neurogenic responses in SHR and WKY animals besides a co-participation of ATP and noradrenaline in both contractile components of the response to EFS.Purinergic and adrenergic components of the contractile response to electrical field stimulation (EFS) have been investigated in epididymal and prostatic portions of Wystar Kyoto (WKY) and spontaneously hypertensive rat (SHR) vas deferens.In both halves of SHR and WKY vas deferens, EFS (40 V, 0.5 ms for 30 s, 0.5–32 Hz) evoked frequency-related contractions. The neurogenic responses were biphasic, consisting of a rapid non-adrenergic response, dominant in the prostatic portion, followed by a slow tonic adrenergic component, dominant in the epididymal half.Phasic and tonic components of the frequency-response curves evoked by EFS were significantly higher in the epididymal but not in the prostatic portion of vas deferens from SHR compared to WKY rats.The α1-adrenoceptor antagonist prazosin (0.1 μM) was more effective against both components of the contractile response in the epididymal end of SHR than in WKY rats.Inhibition by α,β-methylene adenosine 5′-triphosphate (α,β-meATP 3 and 30 μM) was higher in both components of the contractile responses in WKY preparations than in SHR.Combined α1-adrenoceptor and P2x-purinoceptor antagonism virtually abolished the EFS-evoked contractile response in both strains. The degree of inhibition by prazosin (0.1 μM) after P2x-purinoceptor blockade was higher in SHR than in WKY rats.These results demonstrate a modification in the purinergic and noradrenergic contribution to neurogenic responses in SHR and WKY animals besides a co-participation of ATP and noradrenaline in both contractile components of the response to EFS.British Journal of Pharmacology (1999) 128, 873–880; doi:10.1038/sj.bjp.0702845
American Journal of Physiology-heart and Circulatory Physiology, 2007
Transient focal cerebral ischemia in the rat alters vessel properties, and spontaneously hyperten... more Transient focal cerebral ischemia in the rat alters vessel properties, and spontaneously hypertensive rats (SHR) show a poorer outcome after ischemia. Here we examined the role of hypertension on vessel properties after ischemia/reperfusion. The right middle cerebral artery (MCA) was occluded (90 min) and reperfused (24 h) in SHR (n=12) and
Naunyn-schmiedebergs Archives of Pharmacology, 1997
Changes in functional responsiveness to α1-adrenoceptor activation with noradrenaline and in [3H]... more Changes in functional responsiveness to α1-adrenoceptor activation with noradrenaline and in [3H]prazosin binding in the epididymal portion of vas deferens from normotensive Wistar Kyoto (WKY) and spontaneously hypertensive rats (SHR) were investigated. The operational model fitting and the nested hyperbolic method were used to analyze the effects of irreversible receptor alkylation by phenoxybenzamine (0.1 μM) on the α1-adrenoceptor mediated contractile responses to noradrenaline of vasa deferentia from SHR and WKY rats. Saturation isotherms for [3H]prazosin revealed a significant increase (P < 0.05) in the Bmax in SHR vas deferens (145 ± 19 fmol/mg protein) compared with vas deferens from normotensive controls (75 ± 12 fmol/mg protein) without changes in the KD. No differences in the proportion of high and low affinity binding sites for WB-4101 and 5-methylurapidil were observed. The maximum contractile response, α, (P < 0.001) and the pEC50 (P < 0.05) values for noradrenaline were greater for SHR than for WKY rat tissues. The apparent affinity (pKA) determined by the nested hyperbolic method and by the operational model of agonism was found to be similar in the two strains. In agreement with relative pEC50, the efficacy (τ) value for SHR was greater than for WKY rats. However, the difference in the τ estimates did not reach statistical significance. In summary, in the epididymal portion of SHR vas deferens, the increased maximum contractile response to noradrenaline is due to an increase of Em. Taken together, the τ values and the results from binding experiments lead to the assumption that the transducer constant K E must be greater in SHR than in WKY rats, suggesting a deterioration in the transduction of the stimulus provided by the agonist in hypertensive animals.
Autonomic and Autacoid Pharmacology, 2005
1 Our aim was to study the role of nitric oxide (NO) and arachidonic acid pathways in the α1-adre... more 1 Our aim was to study the role of nitric oxide (NO) and arachidonic acid pathways in the α1-adrenoceptor-mediated vasoconstriction in mesenteric resistance arteries from 3–4 and 22 to 23-month-old Sprague-Dawley rats.2 The expression of NO synthase (NOS), cyclooxygenase (COX) isoforms, soluble guanylate cyclase, superoxide dismutase and the NAD(P)H oxidase subunits p22phox and p47phox were determined.3 The NG-nitro-l-arginine methyl ester, a non-selective NOS inhibitor, shifted to the left but indomethacin and NS 398, non-selective and selective COX-2 inhibitors, shifted to the right the concentration-response curve for the vasoconstriction by phenylephrine in both age groups.4 Ageing up-regulated endothelial NOS and p22phox expression but did not modify COX, soluble guanylate cyclase, superoxide dismutase and p47phox expression.5 These data suggest that the observed enhancement of eNOS protein expression could constitute a compensatory mechanism to counter-regulate a chronic loss of NO possibly through increased superoxide anion production from NAD(P)H oxidase induced by age.
Naunyn-schmiedebergs Archives of Pharmacology, 2002
The main objective of this study has been to analyse the electrophysiological differences in the ... more The main objective of this study has been to analyse the electrophysiological differences in the prostatic portion of vas deferens between spontaneously hypertensive (SHR) and Wistar Kyoto rats (WKY). Resting membrane potentials (RMP) recorded in SHR (–63.8±0.3 mV) and WKY (–68.1±0.3 mV) were significantly different. Bath applications of suramin (30 µM), α,β-methylene adenosine 5'-triphosphate (α,β-meATP; 30 µM) or prazosin (0.1 µM) did not modify the control values of RMP. In control conditions, spontaneous excitatory junction potentials (SEJPs) were recorded in preparations from both groups of animals. SEJPs registered in SHR were greater than those in WKY in amplitude (7.0±0.4 mV vs. 2.6±0.1 mV) and frequency (0.25±0.02 Hz vs. 0.14±0.01 Hz). SEJP amplitude was abolished by bath applications of suramin (30 µM) or α,β-meATP (30 µM). However, tetrodotoxin (TTX; 1 µM) and prazosin (0.1 µM) had no effect on this spontaneous activity. Electrical-field stimulation (EFS; 0.1 ms, 20 V, 0.2 Hz) induced an enhanced excitatory junction potential (EJP) in SHR but not in WKY (16.0±0.6 mV vs. 12.2±0.5 mV) which was abolished by TTX (1 µM), suramin (30 µM) and α,β-meATP (30 µM). The degree of inhibition of both SEJP and EJP produced by α,β-meATP (0.3–30 µM) was greater in SHR than in WKY. This study demonstrates an altered purinergic contribution to the co-transmission process in the prostatic portion of vas deferens from SHR.
Transient focal cerebral ischemia in the rat alters vessel properties, and spontaneously hyperten... more Transient focal cerebral ischemia in the rat alters vessel properties, and spontaneously hypertensive rats (SHR) show a poorer outcome after ischemia. Here we examined the role of hypertension on vessel properties after ischemia/reperfusion. The right middle cerebral artery (MCA) was occluded (90 min) and reperfused (24 h) in SHR (n=12) and
Pharmacology & Therapeutics, 2002
Modeling the shape of concentration-effect curves is of prime importance in pharmacology. Geometr... more Modeling the shape of concentration-effect curves is of prime importance in pharmacology. Geometric descriptors characterizing these curves (the upper and lower asymptotes, the mid-point, the mid-point slope, and the point of inflection) are used for drug comparison or for assessing the change in agonist function after a system modification. The symmetry or asymmetry around the mid-point of a concentration-effect curve is a fundamental property that, regretfully, is often overlooked because, generally, models yielding exclusively symmetric curves are used. In the present review, empirical and mechanistic models are examined in their ability to fit experimental data. The geometric parameters of a survey of empirical models, the Hill equation, a logistic variant that we call the modified Hill equation, the Richards function, and the Gompertz model are determined. To analyze the relationship between asymmetry and mechanism, some examples from the ionic channel field, in an increasing degree of complexity, are used. It is shown that asymmetry arises from ionic channels with multiple binding sites that are partly occupied. The operational model of agonism is discussed both in its empirical general formulation and including the signal transduction mechanisms through G-protein-coupled receptors. It is shown that asymmetry results from systems where receptor distribution is allowed. Developed mathematical models are compared for describing experimental data on α-adrenoceptors. The existence or not of a relationship between the shape of the curves and receptor reserve is discussed.
Journal of Pharmacology and Experimental Therapeutics, 2005
List of non-standard abreviation: 8-Br-cGMP, 8-Bromoguanosine 3',5'-cyclic monophosphate IL-1ß, i... more List of non-standard abreviation: 8-Br-cGMP, 8-Bromoguanosine 3',5'-cyclic monophosphate IL-1ß, interleukin-1ß eNOS, endothelial nitric oxide synthase iNOS, inducible nitric oxide synthase L-NAME, N w -Nitro-L -Arginine Methyl Ester MRA, mesenteric resistance arteries NO, nitric oxide sGC, soluble guanylate cyclase PEG-SOD, polyethylene glycol superoxide dismutase JPET #88435 3 SNP, sodium nitroprusside TNF-α, tumor necrosis factor-α 1400W, N-3-aminomethylbenzylacetamidine Section Assignment: Cardiovascular JPET #88435 4 Abstract The present study was designed to analyze the effect of long term incubation with interleukin 1ß (IL-1ß) on endothelium-dependent relaxation in rat mesenteric resistance arteries. Vessels were incubated in culture medium with or without IL-1ß (10 ng/ml, 14 h). Changes in lumen diameter were recorded in a pressure myograph. Protein expression, nitrite and superoxide anion (O 2 .-) production were evaluated by either Western blot or immunofluorescence, Griess reaction and ethidium fluorescence, respectively. IL-1ß impaired acetylcholine (ACh) and sodium nitroprusside (SNP) vasodilation and increased nitrite and O 2 .production and inducible nitric oxide synthase (iNOS), xanthine oxidase and p22 phox expression. However, neither endothelial NOS nor soluble guanylate cyclase protein expression were affected by IL-1ß treatment. Polyethylene glycol superoxide dismutase partially reversed the impairment of ACh relaxation and abolished the O 2 .production observed in IL-1ß treated arteries. The impairment of ACh relaxation induced by IL-1ß was also partially reversed by the xanthine oxidase inhibitor, allopurinol (1 mM), but not by either the NADPH oxidase inhibitor, apocynine (0.3 mM) or the iNOS inhibitor, 1400W (1 µM). However, all these inhibitors improved the impaired SNP response. The results of the present study demonstrate that long-term incubation with IL-1ß induces an impairment of the nitric mediated relaxation in mesenteric resistance arteries through the production of O 2 .mainly from xanthine oxidase. JPET #88435 5
British Journal of Pharmacology, 1997
We have studied the α1-adrenoceptor-mediated responses in intact tail artery rings from 3–4 and 2... more We have studied the α1-adrenoceptor-mediated responses in intact tail artery rings from 3–4 and 20–22 months old Sprague-Dawley rats, focusing on possible endothelial alterations. The influence of nitric oxide released by the endothelium, the number of α1-adrenoceptors and the functional receptor reserve were evaluated to determine their contribution to the contractile response mediated by this receptor. The state of the endothelial layer was assessed by confocal microscopy.Noradrenaline (1 nM–100 μM) induced concentration-dependent vasoconstriction. The maximum contractions to noradrenaline (P<0.05) and to 75 mM KCl (P<0.01) were higher in young than in old animals.The density (Bmax) of α1-adrenoceptors and the dissociation constant (KD) obtained in [3H]-prazosin binding experiments were unchanged by age.The apparent affinity (pKA) and the percentage of functional receptors (qx100) remaining after phenoxybenzamine (0.03 μM) were similar in both age groups.After partial α1-adrenoceptor inactivation with phenoxybenzamine, NG-nitro-L-arginine methylester (30 μM) significantly potentiated the E/[A] curve to noradrenaline in young rats. However, only responses to 0.1 to 1 μM noradrenaline were significantly potentiated in old animals. In addition, 94% of the vessels from young, but only 52% from old rats were relaxed by 80–100% of the noradrenaline (0.03 μM) contraction, with 1 μM acetylcholine.No modifications in the area (μm2) or in the number of endothelial nuclei (per mm2) were observed between age groups. An elongation of the nuclei of endothelial cells was observed in the old animals.These data suggest that the noradrenaline-induced contraction is decreased in old rats probably due to differences in either the contractile machinery or postreceptor mechanisms. These alterations may be accompanied by an impairment of the release or production of NO from endothelial cells.We have studied the α1-adrenoceptor-mediated responses in intact tail artery rings from 3–4 and 20–22 months old Sprague-Dawley rats, focusing on possible endothelial alterations. The influence of nitric oxide released by the endothelium, the number of α1-adrenoceptors and the functional receptor reserve were evaluated to determine their contribution to the contractile response mediated by this receptor. The state of the endothelial layer was assessed by confocal microscopy.Noradrenaline (1 nM–100 μM) induced concentration-dependent vasoconstriction. The maximum contractions to noradrenaline (P<0.05) and to 75 mM KCl (P<0.01) were higher in young than in old animals.The density (Bmax) of α1-adrenoceptors and the dissociation constant (KD) obtained in [3H]-prazosin binding experiments were unchanged by age.The apparent affinity (pKA) and the percentage of functional receptors (qx100) remaining after phenoxybenzamine (0.03 μM) were similar in both age groups.After partial α1-adrenoceptor inactivation with phenoxybenzamine, NG-nitro-L-arginine methylester (30 μM) significantly potentiated the E/[A] curve to noradrenaline in young rats. However, only responses to 0.1 to 1 μM noradrenaline were significantly potentiated in old animals. In addition, 94% of the vessels from young, but only 52% from old rats were relaxed by 80–100% of the noradrenaline (0.03 μM) contraction, with 1 μM acetylcholine.No modifications in the area (μm2) or in the number of endothelial nuclei (per mm2) were observed between age groups. An elongation of the nuclei of endothelial cells was observed in the old animals.These data suggest that the noradrenaline-induced contraction is decreased in old rats probably due to differences in either the contractile machinery or postreceptor mechanisms. These alterations may be accompanied by an impairment of the release or production of NO from endothelial cells.
British Journal of Pharmacology, 1997
The influence of l-NG-nitro-arginine (l-NOARG, 30 μm) on contractile responses to exogenous norad... more The influence of l-NG-nitro-arginine (l-NOARG, 30 μm) on contractile responses to exogenous noradrenaline was studied in the rat anococcygeus muscle.Noradrenaline (0.1–100 μm) contracted the muscle in a concentration-dependent manner. l-NOARG (30 μm) had no effect on noradrenaline responses.Phenoxybenzamine (Pbz 0.1 μm) depressed by 46% (P<0.001) the maximum response and shifted to the right (P<0.001) the E/[A] curve to noradrenaline (pEC50 control: 6.92±0.09; pEC50 Pbz: 5.30±0.10; n=20).The nested hyperbolic null method of analysing noradrenaline responses after phenoxybenzamine showed that only 0.61% of the receptors need to be occupied to elicit 50% of the maximum response, indicating a very high functional receptor reserve.Contractile responses to noradrenaline after partial α1-adrenoceptor alkylation with phenoxybenzamine (0.1 μm) were clearly enhanced by l-NOARG.The potentiating effect of l-NOARG on noradrenaline responses after phenoxybenzamine was reversed by (100 μm) l-arginine but not by (100 μm) d-arginine.These results indicate that spontaneous release of NO by nitrergic nerves can influence the α1-adrenoceptor-mediated response to exogenous noradrenaline.The influence of l-NG-nitro-arginine (l-NOARG, 30 μm) on contractile responses to exogenous noradrenaline was studied in the rat anococcygeus muscle.Noradrenaline (0.1–100 μm) contracted the muscle in a concentration-dependent manner. l-NOARG (30 μm) had no effect on noradrenaline responses.Phenoxybenzamine (Pbz 0.1 μm) depressed by 46% (P<0.001) the maximum response and shifted to the right (P<0.001) the E/[A] curve to noradrenaline (pEC50 control: 6.92±0.09; pEC50 Pbz: 5.30±0.10; n=20).The nested hyperbolic null method of analysing noradrenaline responses after phenoxybenzamine showed that only 0.61% of the receptors need to be occupied to elicit 50% of the maximum response, indicating a very high functional receptor reserve.Contractile responses to noradrenaline after partial α1-adrenoceptor alkylation with phenoxybenzamine (0.1 μm) were clearly enhanced by l-NOARG.The potentiating effect of l-NOARG on noradrenaline responses after phenoxybenzamine was reversed by (100 μm) l-arginine but not by (100 μm) d-arginine.These results indicate that spontaneous release of NO by nitrergic nerves can influence the α1-adrenoceptor-mediated response to exogenous noradrenaline.British Journal of Pharmacology (1997) 120, 1035–1038; doi:10.1038/sj.bjp.0701005
Journal of Autonomic Pharmacology, 1999
1 The present study focuses on the role of endothelium on a 1 -adrenoceptor-mediated vasoconstric... more 1 The present study focuses on the role of endothelium on a 1 -adrenoceptor-mediated vasoconstriction in aorta from Wistar Kyoto (WKY) and spontaneously hypertensive rats (SHR). To define and quantify changes in the parameters governing agonism at a 1 -adrenoceptor by hypertension and/or endothelium, the operational model of analysis was used. 2 In either endothelium intact or denuded aorta, the sensitivity (P < 0.001) and the maximum contraction (P < 0.05) to phenylephrine were smaller in SHR than in WKY. 3 However, in each strain of rats, removal of endothelium increased the sensitivity (P < 0.001) to phenylephrine but reduced (P < 0.05) KCl-evoked vasoconstriction, suggesting a modulation of these responses by the endothelium. The observed differences in sensitivity and maximum contraction are interpreted in terms of the operational parameters: E m , the maximum possible effect; pK A , the agonist affinity; a, the agonist efficacy and n, the slope for the function relating receptor occupancy to pharmacological effect. The estimated parameters reflected differences, between strains, in the signal transduction processes linked to a 1 -adrenoceptor stimulation ascribed to the presence of the endothelium. 4 N G -nitro-l-arginine methyl ester (L-NAME), enhanced to a similar extend in both rat strains the sensitivity (P < 0.001) and the maximum contraction to phenylephrine. Indomethacin reduced the maximum contraction to phenylephrine by 56.85% in SHR and by 11.80% in WKY suggesting that contracting prostanoids play a more major role in this response in SHR than in WKY. Nevertheless, these inhibitors were without effect on denuded vessels from both strains suggesting that NO and cyclooxygenase products from the media or the adventitia do not play a role on the phenylephrinemediated responses. 5 The studied endothelial factors partially explain the observed differences in modulation of a 1adrenoceptor responses by the endothelium but suggest the participation of other compounds released by the endothelium.
British Journal of Pharmacology, 2003
There is a long-known hyper-responsiveness of vascular adrenergic transmission in the spontaneous... more There is a long-known hyper-responsiveness of vascular adrenergic transmission in the spontaneously hypertensive rat (SHR) that is uncovered specifically in the presence of cocaine and attributed to blockade of the neuronal monoamine transporter. We have now used the rat anococcygeus muscle to investigate whether this phenomenon is generic to sympathetic transmission to smooth muscle rather than a purely vascular phenomenon. We sought the origin of the effect by successively blocking the buffering effects of the neuronal monoamine transporter, prejunctional α2-adrenoceptors and NO from nitrergic nerves with desipramine (0.1 μM), rauwolscine (0.01 μM) and L-NG-nitro-arginine (100 μM).In the presence of desipramine, contractile responses to electrical field stimulation but not to noradrenaline (1 nM–100 μM) were greater in SHR than in Wistar–Kyoto (WKY). Neither inhibition of prejunctional α2-adrenoceptors nor the blockade of neuronal nitric oxide synthase (nNOS) accounted for the differential enhancement of response in SHR. The enhanced effectiveness of motor neurotransmission in SHR becomes most apparent when all known major buffering mechanisms are removed.When nitrergic responses were isolated pharmacologically (phentolamine 1 μM and guanethidine 30 μM; tone raised with carbachol 50 μM), they were not different between SHR and WKY.Western blots showed that both nNOS and tyrosine hydroxylase are expressed to a similar extent in anococcygeus muscle from SHR and WKY, suggesting similar adrenergic and nitrergic innervations in the two strains. This suggests that enhanced motor transmission is due to increased transmitter release per varicosity rather than there being normal transmission from a greater number of sites.We conclude that there is a generic enhancement of sympathetic transmission in SHR rather than this being a vascular phenomenon.There is a long-known hyper-responsiveness of vascular adrenergic transmission in the spontaneously hypertensive rat (SHR) that is uncovered specifically in the presence of cocaine and attributed to blockade of the neuronal monoamine transporter. We have now used the rat anococcygeus muscle to investigate whether this phenomenon is generic to sympathetic transmission to smooth muscle rather than a purely vascular phenomenon. We sought the origin of the effect by successively blocking the buffering effects of the neuronal monoamine transporter, prejunctional α2-adrenoceptors and NO from nitrergic nerves with desipramine (0.1 μM), rauwolscine (0.01 μM) and L-NG-nitro-arginine (100 μM).In the presence of desipramine, contractile responses to electrical field stimulation but not to noradrenaline (1 nM–100 μM) were greater in SHR than in Wistar–Kyoto (WKY). Neither inhibition of prejunctional α2-adrenoceptors nor the blockade of neuronal nitric oxide synthase (nNOS) accounted for the differential enhancement of response in SHR. The enhanced effectiveness of motor neurotransmission in SHR becomes most apparent when all known major buffering mechanisms are removed.When nitrergic responses were isolated pharmacologically (phentolamine 1 μM and guanethidine 30 μM; tone raised with carbachol 50 μM), they were not different between SHR and WKY.Western blots showed that both nNOS and tyrosine hydroxylase are expressed to a similar extent in anococcygeus muscle from SHR and WKY, suggesting similar adrenergic and nitrergic innervations in the two strains. This suggests that enhanced motor transmission is due to increased transmitter release per varicosity rather than there being normal transmission from a greater number of sites.We conclude that there is a generic enhancement of sympathetic transmission in SHR rather than this being a vascular phenomenon.British Journal of Pharmacology (2003) 140, 773–779. doi:10.1038/sj.bjp.0705480