Author:

Keywords:

Animals, Autonomic Nervous System, Electric Stimulation, Feedback, Gastric Fundus, Isometric Contraction, Male, Molsidomine, Muscle Relaxation, Muscle, Smooth, Nitric Oxide, Nitroglycerin, Rats, Rats, Wistar, Vasoactive Intestinal Peptide, Vasodilator Agents, Science & Technology, Life Sciences & Biomedicine, Pharmacology & Pharmacy, FEEDBACK INHIBITION, NITRERGIC NERVE, NITRIC OXIDE (NO), NANC (NONADRENERGIC NONCHOLINERGIC), GASTRIC FUNDUS, (RAT), RAT GASTRIC FUNDUS, VASOACTIVE INTESTINAL POLYPEPTIDE, NONADRENERGIC NONCHOLINERGIC NERVES, L-ARGININE, RELEASE, NEUROTRANSMISSION, SYNTHASE, STIMULATION, MUSCLE, CELLS, In Vitro Techniques, 0801 Artificial Intelligence and Image Processing, 1115 Pharmacology and Pharmaceutical Sciences, 1701 Psychology, 1702 Cognitive Sciences, 3214 Pharmacology and pharmaceutical sciences

Abstract:

The effects of pretreatment with the nitric oxide (NO)-releasing substances 3-morpholino-sydnoninime (SIN-1) and nitroglycerin were investigated on relaxations induced by non-adrenergic non-cholinergic (NANC) nerve stimulation, authentic NO and vasoactive intestinal polypeptide (VIP) in the rat gastric fundus. Short periods of electrical stimulation (0.5-16 Hz, 1 ms, pulse trains of 10 s) induced frequency-dependent transient relaxations, previously shown to be mainly mediated by NO. Both SIN-1 (10-100 microM) and nitroglycerin (0.5 mM) pretreatment significantly reduced these electrically induced responses to a similar extent as the inhibitor of the NO biosynthesis L-nitroarginine (30-300 microM). Prolonged periods of electrical stimulation (16 Hz, 1 ms, pulse trains of 180 s) induced a sustained relaxation, previously shown to be mediated by NO and VIP. L-Nitroarginine (30-300 microM) or pretreatment with SIN-1 (100 microM) or nitroglycerin (0.5 mM) did not affect the amplitude of this relaxation but slowed down its onset. Authentic NO (0.01-10 microM) and VIP (0.01-10 nM) induced respectively transient and sustained concentration-dependent relaxations. SIN-1 or nitroglycerin pretreatment had no effect on the concentration-response curves to NO and VIP. These results indicate that prolonged exposure to NO donors inhibits electrically induced nerve-mediated NANC relaxations without affecting the postjunctional response to NO and VIP. As similar results are obtained with NO biosynthesis inhibitors, our results illustrate a prejunctional inhibitory effect of NO on the NANC nerves of the rat gastric fundus and suggest the presence of an autoregulatory mechanism for the nitrergic innervation.