Martha I. Dávila-García | Howard University (original) (raw)
Papers by Martha I. Dávila-García
Journal of Neurochemistry, Jun 28, 2008
A synthetic peptide corresponding to the C‐terminus of the α3 subunit of the rat neuronal nicotin... more A synthetic peptide corresponding to the C‐terminus of the α3 subunit of the rat neuronal nicotinic acetylcholine receptor (nAChR) was used to generate a rabbit polyclonal α3 antibody. The specificity of this antibody was characterized by immunoblotting, immunohistochemical and immunoprecipitation techniques. Using this antibody, the relative densities of the α3 subunit were quantitatively determined in different brain regions and in superior cervical ganglion (SCG). Among these regions, SCG, interpeduncular nucleus (IPN) and pineal gland showed the highest levels of α3 protein expression. Habenula and superior colliculi had intermediate levels of expression. Low levels were found in cerebral cortex, hippocampus and cerebellum. The ontogenic profile of the α3 subunit in the SCG was also determined. The α3 protein level is low at postnatal day (P 1), but increases rapidly during the first seven postnatal days. This level then plateaus and remains stable through postnatal day 35. These findings suggest that neuronal nAChRs containing the α3 subunit participate in important roles in specific regions of the rat brain and the SCG.
Developmental Brain Research, Sep 1, 1989
Leu-enkephalin, at concentrations between 18 microM and 1.8 pM, was administered in a single or d... more Leu-enkephalin, at concentrations between 18 microM and 1.8 pM, was administered in a single or daily dose to dissociated mesencephalic raphe cell cultures maintained for 3 or 5 days. Daily administration of Leu-enkephalin produced an inhibition of high affinity uptake of [3H]5-HT, a measure of serotonergic process outgrowth in cultures of fetal neurons. This inhibition was maximal at a dose of 18 nM in both 3 (59%, P less than 0.05)- and 5 (38%, P less than 0.05)-day cultures. The expression of uptake was consistently lower in 5-day cultures than in 3-day cultures at all concentrations tested. In marked contrast, a single dose of Leu-enkephalin at the time of plating stimulated uptake in 3- and 5-day cultures. Maximal stimulation was observed at 180 nM for both 3 (191%, P less than 0.05)- and 5 (140%, P less than 0.05)-day cultures. The results obtained after a single dose of the opioid may reflect a paradoxical stimulation probably due to a rebound mechanism of receptors since co-administration of bacitracin (0.5 mg/ml), an aminopeptidase inhibitor, resulted in inhibition of the uptake expression. Together these results indicate that Leu-enkephalin can function as an inhibitory regulatory growth factor for neuronal cultures when constant exposure to this opioid is maintained over time.
International Journal of Developmental Neuroscience, 1991
These studies were designed to examine the differential effects of prenatal or postnatal administ... more These studies were designed to examine the differential effects of prenatal or postnatal administration of ACTH 1‐39 and nicotine, on 5‐HT high affinity uptake in brainstem and hippocampal synaptosomes. ACTH was administered prenatally (to pregnant dams) and postnatally to the neonates. Postnatal administration of ACTH significantly increased high‐affinity 5‐HT uptake in the hippocampus and especially the brainstem at both 7 and 21 days after birth. Prenatal ACTH, on the other hand, transiently increased 5‐HT uptake in only the brainstem at 7 days, a change that was reversed at 21 days. While the effects of postnatal nicotine administration were essentially the same as those of postnatal ACTH treatment, prenatal nicotine, unlike ACTH, did not alter 5‐HT uptake in 7‐day‐old rats but did reduce uptake in both tissues at 21 days. The observation that postnatal nicotine mimics the effects of postnatal ACTH and that nicotine stimulates ACTH release, suggests that the postnatal effects of nicotine may be exerted through ACTH.
Annals of the New York Academy of Sciences, 1990
... of Biology New York University New York, New York 10003 MAYA FRANKFURT The ... the dorsal hip... more ... of Biology New York University New York, New York 10003 MAYA FRANKFURT The ... the dorsal hippocampus, then the atropine injection is no longer effective at disrupting memory. Thus, in cortically based cognitive behaviors, fetal serotonergic neurons provide the input for ...
Journal of Pharmacology and Experimental Therapeutics
ABSTRACT
Journal of Alcoholism & Drug Dependence, 2017
Orexin/hypocretin-containing neurons in lateral hypothalamus (LH) are implicated in the neurobiol... more Orexin/hypocretin-containing neurons in lateral hypothalamus (LH) are implicated in the neurobiology of nicotine addiction. However, the neuroanatomical relationships between orexinneurons/nerve fibers and nicotine-activated cells within the reward-addiction neurocircuitry is not known. In the present study in mice, we first used c-Fos immunohistochemistry to identify CNS cells stimulated by an acute single injection of nicotine (NIC, 2 mg/kg, IP). Sequential doublelabelling was then performed to identify the location of orexin-containing neurons and nerve fibers with respect to NIC-induced c-Fos activated cells and/or tyrosine hydroxylase (TH) immunoreactive (IR) cells of the mesocorticolimbic reward-addiction pathways. Orexin-IR nerve fibers and terminals were detected at multiple sites of the NIC reward-addiction circuitry in close apposition to, and intermingled with, NIC-induced c-Fos-IR cells of locus coeruleus (LC), ventral tegmental area (VTA), nucleus accumbens (Acb), LH and paraventricular thalamic nucleus (PVT). Double-labelling of orexin with TH showed frequent contact between orexin-IR nerve fibers and noradrenergic cells of LC. However, there was infrequent contact between the orexinergic fibers and the TH-expressing dopaminergic cells of VTA, dorsal raphe nucleus (DR), posterior hypothalamus (DA11), arcuate hypothalamic nucleus (DA12) and periventricular areas (DA14). The close anatomical contact between orexinergic nerve fibers and NIC-activated cells at multiple sites of the reward-addiction pathways suggests that orexinergic projections from LH are likely to This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Molecular Pharmacology
ABSTRACT
The FASEB Journal, 2007
Previous data from this laboratory and others indicate that there is an asymmetry in the distribu... more Previous data from this laboratory and others indicate that there is an asymmetry in the distribution of neurons within the nucleus ambiguus (NA) which project to different intracardiac postganglio...
The FASEB Journal, 2014
The development of subtype-selective ligands for nAChRs holds high potential for better, more tar... more The development of subtype-selective ligands for nAChRs holds high potential for better, more targeted therapeutic management of conditions where nicotinic acetylcholine receptors are implicated, i...
This artic e has not been copyedited and formatt d. The final version may differ from this version.
Neurochemical Research, 2015
Nicotinic acetylcholine receptors (nAChRs) play a crucial role in a number of clinically relevant... more Nicotinic acetylcholine receptors (nAChRs) play a crucial role in a number of clinically relevant mental and neurological pathways, as well as autonomic and immune functions. The development of subtype-selective ligands for nAChRs therefore is potentially useful for targeted therapeutic management of conditions where nAChRs are involved. We tested if selectivity for a particular nAChR subtype can be achieved through small structural modifications of a lead compound containing the nicotinic pharmacophore by changing the distance between the electronegative elements. For this purpose, analogs of A-84543 were designed, synthesized and characterized as potentially new nAChR subtype-selective ligands. Compounds were tested for their binding properties in rat cerebral cortical tissue homogenates, and subtype-selectivity was determined using stably transfected HEK cells expressing different nAChR subtypes. All compounds synthesized were found to competitively displace [ 3 H]-epibatidine ([ 3 H]EB) from the nAChR binding site. Of all the analogues, H-11MNH showed highest affinity for nAChRs compared to a ~ 5 to10-fold lower affinity of A-84543. All other compounds had affinities > 10,000 nM. Both A-84543 and H-11MNH have highest affinity for α2β2 and α4β2 nAChRs and show moderate affinity for β4and α7-containing receptors. H-11MNH was found to be a full agonist with high potency at α3β4, while A-84543 is a partial agonist with low potency. Based on their unique pharmacological binding properties we suggest that A-84543 and its desmethylpyrrolidine analog can be useful as pharmacological ligands for studying nAChRs if selective pharmacological and/or genetic tools are used to mask the function of other receptors subtypes.
Effects of Nicotine on Biological Systems II, 1995
We used [3H]cytisine to characterize nicotinic cholinergic receptor binding sites in rat brain ne... more We used [3H]cytisine to characterize nicotinic cholinergic receptor binding sites in rat brain neurons grown in culture. Primary cells were obtained from several different areas of fetal rat brain at 18 days gestation and were kept in culture for up to 15 days. [3H] Cytisine binds with high affinity to primary cultures of neurons from cerebral cortex, hippocampus and striatum; but the highest binding (≈ 50 fmol/mg protein) was found in neurons from a region containing thalamus, midbrain and brainstem, which we refer to here as the TMB. Culturing cortical neurons in the presence of nicotine for 7 days increases the number of nicotinic receptor binding sites labeled by [3H]cytisine. Primary neuronal cultures should be useful as model systems for studies of subunit composition and molecular mechanisms involved in the regulation of neuronal nicotinic receptors.
Background: Menthol, a commonly used flavoring additive in cigarettes has been found to facilitat... more Background: Menthol, a commonly used flavoring additive in cigarettes has been found to facilitate smoking initiation and nicotine addiction. However, the neuroanatomical and neurochemical targets of menthol within the reward-addiction neurocircuitry remain unknown. In the present study in mice, we hypothesized that dopaminergic and GABAergic neurons of the reward-addiction circuitry are among the initial targets of menthol in the CNS.
Journal of psychopharmacology (Oxford, England), 2017
Mentholated cigarettes capture a quarter of the US market, and are disproportionately smoked by a... more Mentholated cigarettes capture a quarter of the US market, and are disproportionately smoked by adolescents. Menthol allosterically modulates nicotinic acetylcholine receptor function, but its effects on the brain and nicotine addiction are unclear. To determine if menthol is psychoactive, we assessed locomotor sensitization and brain functional connectivity. Adolescent male Sprague Dawley rats were administered nicotine (0.4 mg/kg) daily with or without menthol (0.05 mg/kg or 5.38 mg/kg) for nine days. Following each injection, distance traveled in an open field was recorded. One day after the sensitization experiment, functional connectivity was assessed in awake animals before and after drug administration using magnetic resonance imaging. Menthol (5.38 mg/kg) augmented nicotine-induced locomotor sensitization. Functional connectivity was compared in animals that had received nicotine with or without the 5.38 mg/kg dosage of menthol. Twenty-four hours into withdrawal after the la...
Experientia Supplementum, 1994
The properties of desensitization of nicotinic receptors in synaptosomal preparations isolated fr... more The properties of desensitization of nicotinic receptors in synaptosomal preparations isolated from mouse brain were examined using biochemical assays. While the efflux of 86Rb+ and the release of [3H]dopamine from synaptosomes can be stimulated by nicotine and other nicotinic agonists, and inhibited by nicotinic antagonists, the pharmacological properties of these two processes differ. Prolonged exposure of synaptosomes to activating concentrations of nicotine (0.1 µM – 10 µM) desensitizes both thalamic 86Rb+ efflux and striatal [H]dopamine release. Desensitization can also be observed when the synaptosomes are exposed to nonactivating concentrations of nicotine (1 nM – 100 nM). The kinetics of desensitization of the functional responses are in many ways similar to the kinetics of high affinity [3H]nicotine binding. Both the functional desensitization and the ligand binding are adequately, but not perfectly, explained by the two state model of Katz and Thesleff. The desensitization of 86Rb+ efflux from thalamic synaptosomes varies with the agonist such that the rate of desensitization observed for acetylcholine and other quarternary agonists exceeds that for nicotine or cytisine. The 86Rb+ efflux stimulated by cytisine was substantially lower than that observed for the other agonists. The nicotine-stimulated 86Rb+ efflux is inhibited approximately 50% by the sodium channel antagonist, tetrodotoxin (TTX). The rate of desensitization is reduced somewhat in the presence of 100 nM TTX, but the EC50 for activation by nicotine is unaffected by this toxin. Inclusion of Cs+ or other K+ channel blockers has no effect on either the amount of efflux or the rate of desensitization. Although full responsiveness for nicotine-stimulated [3H]dopamine release recovers when the agonist is removed, the 86Rb+ efflux after desensitization recovers incompletely. These studies demonstrate that nicotinic receptors isolated from brain undergo functional desensitization. Such desensitization may be important in regulating in vivo response to both acute or chronic exposure to nicotine or other agonists. (Supported by DA-03194 and DA-00194).
Human Molecular Genetics, 2007
Studies in cell culture and in animals suggest that neuregulin 1 (NRG1), a probable schizophrenia... more Studies in cell culture and in animals suggest that neuregulin 1 (NRG1), a probable schizophrenia susceptibility gene, regulates the expression of the a7 nicotinic acetylcholine receptors (nAChRs). We hypothesized that schizophrenia-associated allelic variations within the NRG1 gene, via their effects on NRG1 isoform expression, would be associated with alterations in nAChR a7 receptor levels. We examined the effects of four disease-associated single-nucleotide polymorphisms (SNPs) in the 5 0 region of the NRG1 gene on nAChR a7 mRNA transcript expression in both the dorsolateral prefrontal cortex (DLPFC) and hippocampus of normal controls and patients with schizophrenia using quantitative real-time PCR. NRG1 risk alleles at SNPs SNP8NRG221132 and rs6994992 predicted significantly lower nAChR a7 mRNA expression in the DLPFC. Haplotypes containing the risk alleles at the above SNPs were also associated with lower expression of nAChR a7 in the DLPFC. The genotype effect for rs6994992 and the haplotype effect were more pronounced within the schizophrenic patient group. To determine whether receptor levels follow that of mRNA expression, we performed receptor binding and autoradiography using [ 125 I] a-bungarotoxin in the DLPFC. Consistent with the mRNA findings, we found a decrease in binding in risk allele carriers of SNP8NRG221132 as compared with heterozygous individuals. Together, these results suggest that the molecular mechanism of the association between NRG1 risk alleles and schizophrenia may include downregulation of nAChR a7 expression.
... Title, Neuropeptides as endogenous neuronal growth regulatory factors on serotonergic maturat... more ... Title, Neuropeptides as endogenous neuronal growth regulatory factors on serotonergic maturation. Creator/Author, Davila-Garcia, MI. Publication Date, 1989 Jan 01. OSTI Identifier, OSTI ID: 6368121. Resource Type, Miscellaneous. Resource Relation, Thesis (Ph. D.). ...
Neuroscience, Jan 1, 2011
Untimely activation of nicotinic acetylcholine receptor (nAChR) by nicotine results in short-and ... more Untimely activation of nicotinic acetylcholine receptor (nAChR) by nicotine results in short-and long-term consequences on learning and behavior. In this study, the aim was to determine how prenatal nicotine exposure affects components of glutamatergic signaling in the hippocampus during postnatal development. We investigated regulation of both nAChRs and glutamate receptors for α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) and N-methyl-Daspartate (NMDA), from postnatal day (P) 1 to P63 after a temporally restricted exposure to saline or nicotine for 14 days in utero. We analyzed postsynaptic density components associated with AMPAR and NMDAR signaling: Calcium/calmodulin-dependent protein kinase II α (CaMKIIα), Calmodulin (CaM), and postsynaptic density-95 (PSD95), as well as presynaptically localized synaptosomal-associated protein 25 (SNAP25). At P1, there was significantly heightened expression of AMPAR subunit GluR1 but not GluR2, and of NMDAR subunits NR1, NR2a and NR2d but not NR2b. NR2c was not detectable. At P1, the postsynaptic proteins CaMKIIα, CaM, and PSD95 were also significantly upregulated, together with presynaptic SNAP25. This enhanced expression of glutamate receptors and signaling proteins was concomitant with elevated levels of [ 3 H] Epibatidine (EB) binding in prenatal nicotine-exposed hippocampus, indicating that α4β2 nAChR may influence glutamatergic function in the hippocampus at P1. By P14, neither [ 3 H]EB binding nor the expression levels of subunits GluR1, GluR2, NR1, NR2a, NR2b, NR2c, or NR2d seemed changed with prenatal nicotine. However, CaMKIIα was significantly upregulated with nicotine treatment while CaM showed downregulation at P14. The effects of nicotine persisted in young adult brains at P63. They exhibited significantly downregulated GluR2, NR1, and NR2c expression levels in hippocampal homogenates and a considerably muted overall distribution of [ 3 H]AMPA binding in areas CA1, CA2, CA3, and the dentate gyrus. Our results suggest that prenatal nicotine exposure can regulate the glutamatergic signaling system throughout postnatal development by enhancing or inhibiting availability of AMPAR and NMDAR or their signaling components. The persistent depression, in adults, of the requisite NR1 subunit for NMDAR assembly, and of GluR2, important for assembly, trafficking, and biophysical properties of AMPAR, indicates that nicotine may alter ionotropic glutamate receptor stoichiometry and functional properties in adults after prenatally restricted exposure.
Advances in experimental …, Jan 1, 1990
In summary, we have presented evidence that neuropeptides can function as either positive or nega... more In summary, we have presented evidence that neuropeptides can function as either positive or negative growth regulatory factors during development. The ACTH family of peptides appear to act predominantly as a positive growth regulatory factor-enhancing neurite outgrowth, cell survival, biochemical maturation and behavioral expression. These effects of ACTH are most pronounced prior to the time the afferent cell has reached its target. Thus, ACTH may act as a low level general neurotrophic growth regulatory factor. The opioids have the opposite effect. These neuropeptides inhibit neurite extension, cell survival, and biochemical maturation. The effects of these negative growth regulatory factors are observed even when the afferents have reached their targets. The action of the opioids is thought to occur through specific receptors and known second messenger systems. Thus, CNS neuropeptide levels can have important actions in regulating the development of a variety of CNS systems, and permanently influencing the structure and function of the brain.
Journal of Neurochemistry, Jun 28, 2008
A synthetic peptide corresponding to the C‐terminus of the α3 subunit of the rat neuronal nicotin... more A synthetic peptide corresponding to the C‐terminus of the α3 subunit of the rat neuronal nicotinic acetylcholine receptor (nAChR) was used to generate a rabbit polyclonal α3 antibody. The specificity of this antibody was characterized by immunoblotting, immunohistochemical and immunoprecipitation techniques. Using this antibody, the relative densities of the α3 subunit were quantitatively determined in different brain regions and in superior cervical ganglion (SCG). Among these regions, SCG, interpeduncular nucleus (IPN) and pineal gland showed the highest levels of α3 protein expression. Habenula and superior colliculi had intermediate levels of expression. Low levels were found in cerebral cortex, hippocampus and cerebellum. The ontogenic profile of the α3 subunit in the SCG was also determined. The α3 protein level is low at postnatal day (P 1), but increases rapidly during the first seven postnatal days. This level then plateaus and remains stable through postnatal day 35. These findings suggest that neuronal nAChRs containing the α3 subunit participate in important roles in specific regions of the rat brain and the SCG.
Developmental Brain Research, Sep 1, 1989
Leu-enkephalin, at concentrations between 18 microM and 1.8 pM, was administered in a single or d... more Leu-enkephalin, at concentrations between 18 microM and 1.8 pM, was administered in a single or daily dose to dissociated mesencephalic raphe cell cultures maintained for 3 or 5 days. Daily administration of Leu-enkephalin produced an inhibition of high affinity uptake of [3H]5-HT, a measure of serotonergic process outgrowth in cultures of fetal neurons. This inhibition was maximal at a dose of 18 nM in both 3 (59%, P less than 0.05)- and 5 (38%, P less than 0.05)-day cultures. The expression of uptake was consistently lower in 5-day cultures than in 3-day cultures at all concentrations tested. In marked contrast, a single dose of Leu-enkephalin at the time of plating stimulated uptake in 3- and 5-day cultures. Maximal stimulation was observed at 180 nM for both 3 (191%, P less than 0.05)- and 5 (140%, P less than 0.05)-day cultures. The results obtained after a single dose of the opioid may reflect a paradoxical stimulation probably due to a rebound mechanism of receptors since co-administration of bacitracin (0.5 mg/ml), an aminopeptidase inhibitor, resulted in inhibition of the uptake expression. Together these results indicate that Leu-enkephalin can function as an inhibitory regulatory growth factor for neuronal cultures when constant exposure to this opioid is maintained over time.
International Journal of Developmental Neuroscience, 1991
These studies were designed to examine the differential effects of prenatal or postnatal administ... more These studies were designed to examine the differential effects of prenatal or postnatal administration of ACTH 1‐39 and nicotine, on 5‐HT high affinity uptake in brainstem and hippocampal synaptosomes. ACTH was administered prenatally (to pregnant dams) and postnatally to the neonates. Postnatal administration of ACTH significantly increased high‐affinity 5‐HT uptake in the hippocampus and especially the brainstem at both 7 and 21 days after birth. Prenatal ACTH, on the other hand, transiently increased 5‐HT uptake in only the brainstem at 7 days, a change that was reversed at 21 days. While the effects of postnatal nicotine administration were essentially the same as those of postnatal ACTH treatment, prenatal nicotine, unlike ACTH, did not alter 5‐HT uptake in 7‐day‐old rats but did reduce uptake in both tissues at 21 days. The observation that postnatal nicotine mimics the effects of postnatal ACTH and that nicotine stimulates ACTH release, suggests that the postnatal effects of nicotine may be exerted through ACTH.
Annals of the New York Academy of Sciences, 1990
... of Biology New York University New York, New York 10003 MAYA FRANKFURT The ... the dorsal hip... more ... of Biology New York University New York, New York 10003 MAYA FRANKFURT The ... the dorsal hippocampus, then the atropine injection is no longer effective at disrupting memory. Thus, in cortically based cognitive behaviors, fetal serotonergic neurons provide the input for ...
Journal of Pharmacology and Experimental Therapeutics
ABSTRACT
Journal of Alcoholism & Drug Dependence, 2017
Orexin/hypocretin-containing neurons in lateral hypothalamus (LH) are implicated in the neurobiol... more Orexin/hypocretin-containing neurons in lateral hypothalamus (LH) are implicated in the neurobiology of nicotine addiction. However, the neuroanatomical relationships between orexinneurons/nerve fibers and nicotine-activated cells within the reward-addiction neurocircuitry is not known. In the present study in mice, we first used c-Fos immunohistochemistry to identify CNS cells stimulated by an acute single injection of nicotine (NIC, 2 mg/kg, IP). Sequential doublelabelling was then performed to identify the location of orexin-containing neurons and nerve fibers with respect to NIC-induced c-Fos activated cells and/or tyrosine hydroxylase (TH) immunoreactive (IR) cells of the mesocorticolimbic reward-addiction pathways. Orexin-IR nerve fibers and terminals were detected at multiple sites of the NIC reward-addiction circuitry in close apposition to, and intermingled with, NIC-induced c-Fos-IR cells of locus coeruleus (LC), ventral tegmental area (VTA), nucleus accumbens (Acb), LH and paraventricular thalamic nucleus (PVT). Double-labelling of orexin with TH showed frequent contact between orexin-IR nerve fibers and noradrenergic cells of LC. However, there was infrequent contact between the orexinergic fibers and the TH-expressing dopaminergic cells of VTA, dorsal raphe nucleus (DR), posterior hypothalamus (DA11), arcuate hypothalamic nucleus (DA12) and periventricular areas (DA14). The close anatomical contact between orexinergic nerve fibers and NIC-activated cells at multiple sites of the reward-addiction pathways suggests that orexinergic projections from LH are likely to This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Molecular Pharmacology
ABSTRACT
The FASEB Journal, 2007
Previous data from this laboratory and others indicate that there is an asymmetry in the distribu... more Previous data from this laboratory and others indicate that there is an asymmetry in the distribution of neurons within the nucleus ambiguus (NA) which project to different intracardiac postganglio...
The FASEB Journal, 2014
The development of subtype-selective ligands for nAChRs holds high potential for better, more tar... more The development of subtype-selective ligands for nAChRs holds high potential for better, more targeted therapeutic management of conditions where nicotinic acetylcholine receptors are implicated, i...
This artic e has not been copyedited and formatt d. The final version may differ from this version.
Neurochemical Research, 2015
Nicotinic acetylcholine receptors (nAChRs) play a crucial role in a number of clinically relevant... more Nicotinic acetylcholine receptors (nAChRs) play a crucial role in a number of clinically relevant mental and neurological pathways, as well as autonomic and immune functions. The development of subtype-selective ligands for nAChRs therefore is potentially useful for targeted therapeutic management of conditions where nAChRs are involved. We tested if selectivity for a particular nAChR subtype can be achieved through small structural modifications of a lead compound containing the nicotinic pharmacophore by changing the distance between the electronegative elements. For this purpose, analogs of A-84543 were designed, synthesized and characterized as potentially new nAChR subtype-selective ligands. Compounds were tested for their binding properties in rat cerebral cortical tissue homogenates, and subtype-selectivity was determined using stably transfected HEK cells expressing different nAChR subtypes. All compounds synthesized were found to competitively displace [ 3 H]-epibatidine ([ 3 H]EB) from the nAChR binding site. Of all the analogues, H-11MNH showed highest affinity for nAChRs compared to a ~ 5 to10-fold lower affinity of A-84543. All other compounds had affinities > 10,000 nM. Both A-84543 and H-11MNH have highest affinity for α2β2 and α4β2 nAChRs and show moderate affinity for β4and α7-containing receptors. H-11MNH was found to be a full agonist with high potency at α3β4, while A-84543 is a partial agonist with low potency. Based on their unique pharmacological binding properties we suggest that A-84543 and its desmethylpyrrolidine analog can be useful as pharmacological ligands for studying nAChRs if selective pharmacological and/or genetic tools are used to mask the function of other receptors subtypes.
Effects of Nicotine on Biological Systems II, 1995
We used [3H]cytisine to characterize nicotinic cholinergic receptor binding sites in rat brain ne... more We used [3H]cytisine to characterize nicotinic cholinergic receptor binding sites in rat brain neurons grown in culture. Primary cells were obtained from several different areas of fetal rat brain at 18 days gestation and were kept in culture for up to 15 days. [3H] Cytisine binds with high affinity to primary cultures of neurons from cerebral cortex, hippocampus and striatum; but the highest binding (≈ 50 fmol/mg protein) was found in neurons from a region containing thalamus, midbrain and brainstem, which we refer to here as the TMB. Culturing cortical neurons in the presence of nicotine for 7 days increases the number of nicotinic receptor binding sites labeled by [3H]cytisine. Primary neuronal cultures should be useful as model systems for studies of subunit composition and molecular mechanisms involved in the regulation of neuronal nicotinic receptors.
Background: Menthol, a commonly used flavoring additive in cigarettes has been found to facilitat... more Background: Menthol, a commonly used flavoring additive in cigarettes has been found to facilitate smoking initiation and nicotine addiction. However, the neuroanatomical and neurochemical targets of menthol within the reward-addiction neurocircuitry remain unknown. In the present study in mice, we hypothesized that dopaminergic and GABAergic neurons of the reward-addiction circuitry are among the initial targets of menthol in the CNS.
Journal of psychopharmacology (Oxford, England), 2017
Mentholated cigarettes capture a quarter of the US market, and are disproportionately smoked by a... more Mentholated cigarettes capture a quarter of the US market, and are disproportionately smoked by adolescents. Menthol allosterically modulates nicotinic acetylcholine receptor function, but its effects on the brain and nicotine addiction are unclear. To determine if menthol is psychoactive, we assessed locomotor sensitization and brain functional connectivity. Adolescent male Sprague Dawley rats were administered nicotine (0.4 mg/kg) daily with or without menthol (0.05 mg/kg or 5.38 mg/kg) for nine days. Following each injection, distance traveled in an open field was recorded. One day after the sensitization experiment, functional connectivity was assessed in awake animals before and after drug administration using magnetic resonance imaging. Menthol (5.38 mg/kg) augmented nicotine-induced locomotor sensitization. Functional connectivity was compared in animals that had received nicotine with or without the 5.38 mg/kg dosage of menthol. Twenty-four hours into withdrawal after the la...
Experientia Supplementum, 1994
The properties of desensitization of nicotinic receptors in synaptosomal preparations isolated fr... more The properties of desensitization of nicotinic receptors in synaptosomal preparations isolated from mouse brain were examined using biochemical assays. While the efflux of 86Rb+ and the release of [3H]dopamine from synaptosomes can be stimulated by nicotine and other nicotinic agonists, and inhibited by nicotinic antagonists, the pharmacological properties of these two processes differ. Prolonged exposure of synaptosomes to activating concentrations of nicotine (0.1 µM – 10 µM) desensitizes both thalamic 86Rb+ efflux and striatal [H]dopamine release. Desensitization can also be observed when the synaptosomes are exposed to nonactivating concentrations of nicotine (1 nM – 100 nM). The kinetics of desensitization of the functional responses are in many ways similar to the kinetics of high affinity [3H]nicotine binding. Both the functional desensitization and the ligand binding are adequately, but not perfectly, explained by the two state model of Katz and Thesleff. The desensitization of 86Rb+ efflux from thalamic synaptosomes varies with the agonist such that the rate of desensitization observed for acetylcholine and other quarternary agonists exceeds that for nicotine or cytisine. The 86Rb+ efflux stimulated by cytisine was substantially lower than that observed for the other agonists. The nicotine-stimulated 86Rb+ efflux is inhibited approximately 50% by the sodium channel antagonist, tetrodotoxin (TTX). The rate of desensitization is reduced somewhat in the presence of 100 nM TTX, but the EC50 for activation by nicotine is unaffected by this toxin. Inclusion of Cs+ or other K+ channel blockers has no effect on either the amount of efflux or the rate of desensitization. Although full responsiveness for nicotine-stimulated [3H]dopamine release recovers when the agonist is removed, the 86Rb+ efflux after desensitization recovers incompletely. These studies demonstrate that nicotinic receptors isolated from brain undergo functional desensitization. Such desensitization may be important in regulating in vivo response to both acute or chronic exposure to nicotine or other agonists. (Supported by DA-03194 and DA-00194).
Human Molecular Genetics, 2007
Studies in cell culture and in animals suggest that neuregulin 1 (NRG1), a probable schizophrenia... more Studies in cell culture and in animals suggest that neuregulin 1 (NRG1), a probable schizophrenia susceptibility gene, regulates the expression of the a7 nicotinic acetylcholine receptors (nAChRs). We hypothesized that schizophrenia-associated allelic variations within the NRG1 gene, via their effects on NRG1 isoform expression, would be associated with alterations in nAChR a7 receptor levels. We examined the effects of four disease-associated single-nucleotide polymorphisms (SNPs) in the 5 0 region of the NRG1 gene on nAChR a7 mRNA transcript expression in both the dorsolateral prefrontal cortex (DLPFC) and hippocampus of normal controls and patients with schizophrenia using quantitative real-time PCR. NRG1 risk alleles at SNPs SNP8NRG221132 and rs6994992 predicted significantly lower nAChR a7 mRNA expression in the DLPFC. Haplotypes containing the risk alleles at the above SNPs were also associated with lower expression of nAChR a7 in the DLPFC. The genotype effect for rs6994992 and the haplotype effect were more pronounced within the schizophrenic patient group. To determine whether receptor levels follow that of mRNA expression, we performed receptor binding and autoradiography using [ 125 I] a-bungarotoxin in the DLPFC. Consistent with the mRNA findings, we found a decrease in binding in risk allele carriers of SNP8NRG221132 as compared with heterozygous individuals. Together, these results suggest that the molecular mechanism of the association between NRG1 risk alleles and schizophrenia may include downregulation of nAChR a7 expression.
... Title, Neuropeptides as endogenous neuronal growth regulatory factors on serotonergic maturat... more ... Title, Neuropeptides as endogenous neuronal growth regulatory factors on serotonergic maturation. Creator/Author, Davila-Garcia, MI. Publication Date, 1989 Jan 01. OSTI Identifier, OSTI ID: 6368121. Resource Type, Miscellaneous. Resource Relation, Thesis (Ph. D.). ...
Neuroscience, Jan 1, 2011
Untimely activation of nicotinic acetylcholine receptor (nAChR) by nicotine results in short-and ... more Untimely activation of nicotinic acetylcholine receptor (nAChR) by nicotine results in short-and long-term consequences on learning and behavior. In this study, the aim was to determine how prenatal nicotine exposure affects components of glutamatergic signaling in the hippocampus during postnatal development. We investigated regulation of both nAChRs and glutamate receptors for α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) and N-methyl-Daspartate (NMDA), from postnatal day (P) 1 to P63 after a temporally restricted exposure to saline or nicotine for 14 days in utero. We analyzed postsynaptic density components associated with AMPAR and NMDAR signaling: Calcium/calmodulin-dependent protein kinase II α (CaMKIIα), Calmodulin (CaM), and postsynaptic density-95 (PSD95), as well as presynaptically localized synaptosomal-associated protein 25 (SNAP25). At P1, there was significantly heightened expression of AMPAR subunit GluR1 but not GluR2, and of NMDAR subunits NR1, NR2a and NR2d but not NR2b. NR2c was not detectable. At P1, the postsynaptic proteins CaMKIIα, CaM, and PSD95 were also significantly upregulated, together with presynaptic SNAP25. This enhanced expression of glutamate receptors and signaling proteins was concomitant with elevated levels of [ 3 H] Epibatidine (EB) binding in prenatal nicotine-exposed hippocampus, indicating that α4β2 nAChR may influence glutamatergic function in the hippocampus at P1. By P14, neither [ 3 H]EB binding nor the expression levels of subunits GluR1, GluR2, NR1, NR2a, NR2b, NR2c, or NR2d seemed changed with prenatal nicotine. However, CaMKIIα was significantly upregulated with nicotine treatment while CaM showed downregulation at P14. The effects of nicotine persisted in young adult brains at P63. They exhibited significantly downregulated GluR2, NR1, and NR2c expression levels in hippocampal homogenates and a considerably muted overall distribution of [ 3 H]AMPA binding in areas CA1, CA2, CA3, and the dentate gyrus. Our results suggest that prenatal nicotine exposure can regulate the glutamatergic signaling system throughout postnatal development by enhancing or inhibiting availability of AMPAR and NMDAR or their signaling components. The persistent depression, in adults, of the requisite NR1 subunit for NMDAR assembly, and of GluR2, important for assembly, trafficking, and biophysical properties of AMPAR, indicates that nicotine may alter ionotropic glutamate receptor stoichiometry and functional properties in adults after prenatally restricted exposure.
Advances in experimental …, Jan 1, 1990
In summary, we have presented evidence that neuropeptides can function as either positive or nega... more In summary, we have presented evidence that neuropeptides can function as either positive or negative growth regulatory factors during development. The ACTH family of peptides appear to act predominantly as a positive growth regulatory factor-enhancing neurite outgrowth, cell survival, biochemical maturation and behavioral expression. These effects of ACTH are most pronounced prior to the time the afferent cell has reached its target. Thus, ACTH may act as a low level general neurotrophic growth regulatory factor. The opioids have the opposite effect. These neuropeptides inhibit neurite extension, cell survival, and biochemical maturation. The effects of these negative growth regulatory factors are observed even when the afferents have reached their targets. The action of the opioids is thought to occur through specific receptors and known second messenger systems. Thus, CNS neuropeptide levels can have important actions in regulating the development of a variety of CNS systems, and permanently influencing the structure and function of the brain.