Non-adrenergic non-cholinergic relaxation mediated by nitric oxide in the canine ileocolonic junction.
The nature of the inhibitory non-adrenergic non-cholinergic (NANC) neurotransmitter was studied in circular muscle strips of the canine terminal ileum and ileocolonic junction. Nitric oxide (NO) induced tetrodotoxin-resistant NANC relaxation, similar to that induced by electrical stimulation or acetylcholine (ACh). Incubation with the stereospecific inhibitors of NO biosynthesis, NG-monomethyl-L-arginine (L-NMMA) and NG-nitro-L-arginine (L-NNA), resulted in an increase of basal tension in the ileocolonic junction which was partly reversed by L-arginine but not by D-arginine. Moreover, L-NMMA and L-NNA, but not D-NMMA, concentration dependently inhibited the NANC relaxation in response to electrical stimulation and ACh, but not that in response to NO or nitroglycerin. This inhibitory effect was reversed by L-arginine but not by D-arginine. Hemoglobin reduced the NANC relaxation in response to electrical stimulation, ACh and nitroglycerin, and abolished the responses to NO. Our results suggest that NO or a NO releasing substance mediates the NANC relaxation in the canine terminal ileum and ileocolonic junction.
Boeckxstaens
G E
GE
Division of Gastroenterology, Faculty of Medicine, University of Antwerp (UIA), Belgium.
Pelckmans
P A
PA
Bult
H
H
De Man
J G
JG
Herman
A G
AG
Van Maercke
Y M
YM
D000818:Animals; D001120:Arginine / Q000031:analogs & derivatives / Q000494:pharmacology; D001341:Autonomic Nervous System / Q000502:physiology*; D003106:Colon / Q000502:physiology; D004285:Dogs; D004558:Electric Stimulation; D005260:Female; D006454:Hemoglobins / Q000378:metabolism; D007082:Ileum / Q000502:physiology; D007537:Isometric Contraction / Q000187:drug effects; D008297:Male; D009126:Muscle Relaxation / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects*; D018377:Neurotransmitter Agents / Q000378:metabolism; D009569:Nitric Oxide / Q000494:pharmacology*; D019335:Nitroarginine; D013237:Stereoisomerism; D019323:omega-N-Methylarginine
D006454:Hemoglobins; D018377:Neurotransmitter Agents; D019335:Nitroarginine; D019323:omega-N-Methylarginine; D009569:Nitric Oxide; D001120:Arginine