Inhibition of non-adrenergic non-cholinergic relaxations by nitric oxide donors.
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.
De Man
J G
JG
Division of Gastroenterology, University of Antwerp, Faculty of Medicine, Antwerp, Belgium.
Boeckxstaens
G E
GE
De Winter
B Y
BY
Moreels
T G
TG
Herman
A G
AG
Pelckmans
P A
PA
D000818:Animals; D001341:Autonomic Nervous System / Q000502:physiology*; D004558:Electric Stimulation; D005246:Feedback / Q000502:physiology; D005748:Gastric Fundus / Q000187:drug effects / Q000294:innervation; D066298:In Vitro Techniques; D007537:Isometric Contraction / Q000187:drug effects; D008297:Male; D008981:Molsidomine / Q000031:analogs & derivatives / Q000494:pharmacology; D009126:Muscle Relaxation / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects* / Q000294:innervation*; D009569:Nitric Oxide / Q000502:physiology*; D005996:Nitroglycerin / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D014660:Vasoactive Intestinal Peptide / Q000494:pharmacology; D014665:Vasodilator Agents / Q000494:pharmacology
D014665:Vasodilator Agents; D009569:Nitric Oxide; D014660:Vasoactive Intestinal Peptide; C002385:linsidomine; D008981:Molsidomine; D005996:Nitroglycerin