title: K(+)-induced neurogenic relaxation of rat distal colon.
abstract: Relaxations of segments of rat distal colon were elicited by hypertonic solutions of potassium (K(+); final concentration, 20.8 or 50.8 mM). The initial part of the response to K(+) was antagonized by the nerve blocker tetrodotoxin. This effect could, moreover, be significantly antagonized by apamin (a blocker of K(+) channels), reactive blue 2 (a P(2y)-purinoceptor antagonist), N(G)-nitro-L-arginine (an inhibitor of NO synthase), 1H-[1,2,4]- oxadiazolo[4,3-a]quinoxaline-1-one (ODQ; an inhibitor of soluble guanylyl cyclase), or N-[2-(p-bromocinnamylamino)ethyl]-5-isoquinolinesulfonamide (H-89; an inhibitor of cAMP-dependent protein kinase). Sodium nitroprusside (a donor of NO) and vasoactive intestinal peptide (VIP) both relaxed the tissues. The response to sodium nitroprusside was abolished by ODQ and unaffected by H-89, and that to VIP was partially inhibited by VIP(10-28) (a VIP receptor antagonist), ODQ, or H-89. When combining reactive blue 2 and N(G)-nitro-L-arginine, the response to 50.8 mM K(+) was reduced by approximately 70% and was abolished by the concomitant administration of these antagonists and VIP(10-28). ATP, NO, and VIP may, thus, be inhibitory neurotransmitters in rat distal colon.
authors.affiliation: Institute of Surgical Sciences, Department of Surgery, Sahlgrenska University Hospital, Göteborg, Sweden.
authors.forename: L
authors.initials: L
authors.lastname: Börjesson
authors.forename: S
authors.initials: S
authors.lastname: Nordgren
authors.forename: D S
authors.initials: DS
authors.lastname: Delbro
mesh_terms: D000818:Animals; D001030:Apamin / Q000494:pharmacology; D002217:Carbachol / Q000494:pharmacology; D003106:Colon / Q000187:drug effects*; D004347:Drug Interactions; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018738:Hexamethonium / Q000494:pharmacology; D066298:In Vitro Techniques; D008012:Lidocaine / Q000494:pharmacology; D008297:Male; D009126:Muscle Relaxation / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects*; D009424:Nervous System Physiological Phenomena; D009599:Nitroprusside / Q000494:pharmacology; D010208:Papaverine / Q000494:pharmacology; D011188:Potassium / Q000008:administration & dosage / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013779:Tetrodotoxin / Q000494:pharmacology; D014660:Vasoactive Intestinal Peptide / Q000494:pharmacology
chemical_list: D004791:Enzyme Inhibitors; D009599:Nitroprusside; D001030:Apamin; D014660:Vasoactive Intestinal Peptide; D018738:Hexamethonium; D013779:Tetrodotoxin; D002217:Carbachol; D008012:Lidocaine; D010208:Papaverine; D011188:Potassium