The Effect of Nitric Oxide on the Rat Diaphragm at Different Frequencies of Indirect Electrical Stimulation (original) (raw)
Related papers
Bulletin of Egyptian Society for Physiological Sciences, 2007
Background: The free radical gas nitric oxide (NO) exhibits diverse vital roles in the human body. It is now recognized as a major messenger molecule. Neural NOsynthase is present in the sarcolemma of type II skeletal muscle fibers. In rats, the NO synthase pathway is present in skeletal muscle, vascular smooth muscle and motor nerve terminal. However, previous studies did not determine whether NO facilitates or impairs neuromuscular transmission in preparations indirectly stimulated at different frequencies. Aim of work: The study aims to examine the effect of NO in rat neuromuscular preparation at different stimulation frequencies and modulation of its effect by hemoglobin (NO scavenger). Methods: 30 rats were used in the experiment and were divided into 2 groups: GpI: rat diaphragms were electrically stimulated by supramaximal stimuli, at low frequency of 0.5Hz for 0.5msec, directly and indirectly to induce simple muscle twitch, GpII: rat diaphragms were electrically stimulated by high frequency of 100Hz, directly and indirectly to induce tetanic contraction. Rat diaphragms were bathed in Krebs solution. To investigate the effect of NO, Larginine was added to the bath in a dose of 4.7nM/50ml bath. Then bovine Hb (50 nM /50ml bath was added to scavenge NO. A contact time of 3 minutes is allowed for each step and the amplitude of maximal contraction(∆Y), contraction time(∆X), and 1/2 relaxation time (1/2Rt) were measured in GpI, while only amplitude of maximal contraction was measured in GpII. Results: NO significantly increased ∆Y, ∆X and decreased 1/2 Rt when rat diaphragm preparations were stimulated indirectly at low or high frequencies. In contrast, when rat diaphragm preparations were stimulated directly at either low or high frequencies, NO significantly decreased ∆Y, ∆X, and increased 1/2 Rt. Bovine Hb completely reversed the NO effects. Conclusion: We can conclude that NO has dual actions, facilitatory and inhibitory, on skeletal muscle contraction using indirect or direct electrical stimulation respectively at both low and high frequencies. Bovine Hb antagonized the effects of NO in all experimental steps, giving an additional proof that the recorded changes were NO mediated.
Neuroscience and behavioral physiology
Experiments on rat diaphragm muscle showed that the nitric oxide (NO) donors sodium nitroprusside SNP) and S-nitroso-N-acetylpenicillamine (SNAP). as well as L-arginine. a substrate for NO synthesis. decreased the level of muscle fiber hyperpolarization (the H effect) after blockade of cholinoceptors on the postsynaptic membrane by d-tubocurarine in conditions of irreversible inhibition of acetylcholinesterase with armine. Conversely, disruptions to NO synthesis in muscle fibers by the NO synthase blocker NG-nitro-L-arginine methyl ester (L-NAME) led to increases in the H effect both in vitro and in vivo. Inactivated solutions of sodium nitroprusside and inactive forms of arginine and NAME (D-arginine. D-NAME) had no effect on the magnitude of the H effect, while hemoglobin, which efficiently binds NO molecules, blocked the inhibitory effects of sodium nitroprusside. SNAP, and L-arginine on the magnitude of the H effect. All these points provide evidence that NO can function as a mo...
Brazilian Journal of Medical and Biological Research, 2001
In rats, the nitric oxide (NO)-synthase pathway is present in skeletal muscle, vascular smooth muscle, and motor nerve terminals. Effects of NO were previously studied in rat neuromuscular preparations receiving low (0.2 Hz) or high (200 Hz) frequencies of stimulation. The latter frequency has always induced tetanic fade. However, in these previous studies we did not determine whether NO facilitates or impairs the neuromuscular transmission in preparations indirectly stimulated at frequencies which facilitate neuromuscular transmission. Thus, the present study was carried out to examine the effects of NO in rat neuromuscular preparations indirectly stimulated at 5 and 50 Hz. The amplitude of muscular contraction observed at the end (B) of a 10-s stimulation was taken as the ratio (R) of that obtained at the start (A) (R = B/A). S-nitroso-N-acetylpenicillamine (200 µM), superoxide dismutase (78 U/ml) and L-arginine (4.7 mM), but not D-arginine (4.7-9.4 mM), produced an increase in R (facilitation of neurotransmission) at 5 Hz. However, reduction in the R value (fade of transmission) was observed at 50 Hz. N G-nitro-L-arginine (8.0 mM) antagonized both the facilitatory and inhibitory effects of L-arginine (4.7 mM). The results suggest that NO may modulate the release of acetylcholine by motor nerve terminals.
The effects of exogenous nitric oxide on the function of neuromuscular synapses
2002
Extracellular recording experiments using neuromuscular skin/chest muscle preparations from lake frogs were performed at low extracellular Ca 2+ ion concentrations to study the effect of L-arginine (the substrate for nitric oxide synthesis) and N G -nitro-L-arginine methyl ester (a blocker of NO synthase) on the parameters of evoked transmitter secretion and ion currents in motor nerve endings. L-arginine at a concentration of 100 µM decreased the amplitude of endplate currents as well as their quantum composition, and also increased the amplitude of the third phase of the evoked nerve ending response, which reflects the kinetics of potassium influx currents. N G -nitro-L-arginine methyl ester at a condition of 100 µM led to increases in the amplitude and quantum composition of endplate currents and decreased the amplitude of the third phase of the evoked nerve ending response. It is suggested that endogenous nitric oxide is produced in frog neuromuscular synapses, which in normal conditions suppresses transmitter secretion and modulates the function of potassium channels in the nerve ending.
British Journal of Pharmacology, 1994
The distribution of NADPH-diaphorase positive and catecholamine-containing nerve structures, and functional noradrenergic-nitrergic interactions, were studied in the rat anococcygeus muscle. 2 The morphological findings demonstrated NADPH-diaphorase positive neurones mostly as aggregates in intramural ganglia, nerve tracts and few single nerve fibres forming plexus-like structures. 3 The nitric oxide synthase inhibitor NG-nitro-L-arginine (L-NOARG) inhibited concentrationdependently the nitrergic relaxation, an effect reversed by L-arginine. The drug had dual effects on noradrenergic contractile responses: at lower concentrations (O.1-1OI1M) it decreased the amplitude of contractions and this was not affected by L-arginine; higher concentrations (50-500 JM) potentiated the contractions, an effect that was prevented by L-arginine. 4 The electron acceptor, nitro blue tetrazolium (NBT) produced a rapid inhibition of the noradrenergic contractile responses (EC50 0.178 ± 0.041 JAM). The drug decreased the tone of the preparations. However, it potentiated concentration-dependently the nitrergic relaxations. 5 NBT (1 JAM) had no significant effect on the relaxations induced by exogenously applied nitric oxide (NO)-donor sodium nitroprusside (SNP, 0.01-50 JM). However, the effect of NBT (O.1-1I10 M) on the electrically induced relaxation was significantly decreased by L-NOARG (10 and 50 JAM). The inhibition was of a non-competitive type. 6 Neither L-NOARG (100 JAM) nor NBT (1 JM) had any effect on the spontaneous or electricallyinduced release of 3H-radioactivity from the tissues preincubated in [3H]-noradrenaline. 7 It is concluded that L-arginine-NO pathway can modulate noradrenergic transmission in the rat anococcygeus muscle at postjunctional, but not prejunctional site(s).
Role of Nitric Oxide on Diaphragmatic Muscle Contraction Under Different Frequencies of Stimulation
2017
Background: Nitric oxide (NO) exhibits diverse vital roles in the body functions. It is clearly recognized that NO participates in the control of the vascular tone as an antagonist of adrenergic system. Neural NO-synthase is present in the sarcolemma of type II skeletal muscle fibers. Objective: Evaluating the role of nitric oxide on diaphragmatic muscle contraction under different frequencies of stimulation. Materials and methods: Thirty adult male albino rats weighing 140 155 g were chosen to be the model of the present study. They were divided into two equal groups: Group I (Low frequency stimulated group), and Group II (High frequency stimulated group). Results: NO significantly decreased maximal twitch force (ΔY) and contraction time (ΔX), while increased half relaxation time (1/2 Rt) when the rat diaphragm preparation was stimulated directly at either low (0.5 Hz) or high (100 Hz) frequencies. However, when the preparation was stimulated indirectly at low (0.5 Hz) or high (100...
European Journal of Neuroscience, 2000
After anticholinesterase treatment, the postsynaptic muscle membrane is depolarized by about 5 mV due to nonquantal release of acetylcholine (ACh) from the motor nerve terminal. This can be demonstrated by the hyperpolarization produced by the addition of curare (H-effect). The magnitude of the H-effect was decreased signi®cantly to 3 mV when the nitric oxide (NO) donors, sodium nitroprusside (SNP) and S-nitroso-N-acetylpenicillamine (SNAP) were applied to the muscle, or when NO production was elevated by adding L-arginine, but not D-arginine, as a substrate. The H-effect was increased to 8±9 mV by inhibition of NO synthase by Lnitroarginine methylester (L-NAME), or by guanylyl cyclase inhibition by methylene blue and 1H-[1,2,4]oxidiazolo[4,3-a]quinoxalin-1one (ODQ). ODQ increased the H-effect to 7.3 6 0.2 mV and diminished the SNP-induced decrease of the H-effect when applied together with SNP. The effects of NO donors and L-arginine were eliminated by adding reduced haemoglobin, an extracellular NO scavenger. The present results, together with earlier evidence for the presence of NO synthase in muscle ®bres, indicate that nonquantal release of ACh is modulated by NO production in the postsynaptic cell.
Nitric oxide as a mediator of nonadrenergic noncholinergic neurotransmission
The American journal of physiology, 1992
Part of the regulation of gastrointestinal (GI) smooth muscles is provided by nonadrenergic noncholinergic (NANC) nerves. Stimulation of these nerves, either by field stimulation or via neural reflex pathways, elicits hyperpolarization of postjunctional smooth muscle membranes referred to as inhibitory junction potentials and relaxation. The transmitter(s) that mediate NANC inhibitory neural transmission have been a controversial topic for nearly 30 years. Recent evidence suggests that nitric oxide (NO) may serve as a NANC inhibitory transmitter in the GI tract. This hypothesis is supported by the following. 1) Immunohistochemical studies have shown that the enzyme necessary for NO synthesis is expressed in enteric neurons. In vitro studies of muscles from nearly all levels of GI tract have also shown that arginine analogues, which inhibit NO synthesis, reduce inhibitory effects of NANC neurotransmission. Effects of arginine analogues can be restored by addition of excess L-arginine...
Neurophysiology, 2012
We examined the mechanisms of NO action on transmitter release in neuromuscular preparations of the mouse diaphragm muscle using a standard microelectrode technique. A donor of NO (SNAP, 100 μM) and a substrate for NO synthesis (L-arginine, 100 μM) reduced the evoked transmitter release from motor nerve endings. At the same time, SNAP did not change the frequency and amplitude of miniature end-plate potentials, while an inhibitor of NO synthase, L-NAME, exerted no effect on evoked and spontaneous transmitter release. Inhibition of soluble guanylate cyclase by ODQ (2.5 μM) abolished the effect of NO on the evoked transmitter release, while the elevation of cGMP-level by its membranepenetrating analog 8BrcGMP did not prevent such effect. The elevation of intracellular concentration of cAMP by 100 μM of its analog 8(4CPT) cAMP or inhibition of phosphodiesterase (PDE) by the action of 100 μM IBMX eliminated NO effects on transmitter release. It is concluded that NO activates soluble guanylate cyclase and intensifies the cGMP synthesis. Activation of the PDE II via an increase in the cGMP level with consequent reduction of the level of intracellular cAMP and decrease in the activity of PKA reduced transmitter release from mouse motor nerve ending.
Acta Scientiarum. Biological Sciences, 2004
The research was carried out to verify whether the neuromuscular effects induced by nitric oxide (NO) might depend on extracellular level of Ca ++. The donor of NO, sodium nitroprusside (SNP), and the analogue of cGMP, 8-Br-cGMP, increased the muscular contraction amplitude (MCA) in preparations indirectly stimulated at 0.2 Hz, but did not produce any effect when the nutrient solution was exchanged by Krebs buffer low Ca ++ / high Mg ++. SNP and 8-Br-cGMP reduced the MCA in preparations directly stimulated. Such effect was not recorded in Krebs buffer low Ca ++ / high Mg ++. Data suggest that the neuromuscular effects induced by NO or cGMP depend on extracellular level of Ca ++ .