title: Mode and mechanism of neurotensin action in rat proximal colon.
abstract: This study examined the mechanism of action of neurotensin on intraluminal pressure in rat proximal colon. The direct and indirect contractile response to neurotensin (100 nM) was abolished in Ca(2+)-free solution, and was antagonized by nifedipine (1-5-10 nM) and potentiated by Bay K 8644 (methyl 1,4-dihydro-2,6-dimethyl-3-nitro-4-(2-trifluoromethylphenyl)- pyridine-5-carboxylate) (10-100-1000 nM). Neurotensin, in the presence of nifedipine (10 nM) and atropine (1 microM), induced a tetrodotoxin-insensitive inhibitory effect, which was antagonized by SR 48692 (2[(1-(7-chloro-4-quinolinyl)-5-(2,6-dimethoxy-phenyl)pyrazol-3-yl) carbonyl amino]tricyclo (3.3.1.1.(3.7)) decan-2-carboxylic acid) (300 nM) or apamin (0.1 microM). The results demonstrate that the neurotensin response is dependent on the influx of Ca2+ via L-type channels and results from summation of excitatory and inhibitory effects.
authors.affiliation: Dipartimento di Biologia Cellulare e dello Sviluppo, Università di Palermo, Italy.
authors.forename: F
authors.initials: F
authors.lastname: Mulè
authors.forename: R
authors.initials: R
authors.lastname: Serio
mesh_terms: D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology; D000818:Animals; D001030:Apamin / Q000494:pharmacology; D001285:Atropine / Q000494:pharmacology; D018723:Bethanechol / Q000494:pharmacology; D002118:Calcium / Q000502:physiology; D002120:Calcium Channel Agonists / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D018679:Cholinergic Agonists / Q000494:pharmacology; D018680:Cholinergic Antagonists / Q000494:pharmacology; D003106:Colon / Q000187:drug effects*; D066298:In Vitro Techniques; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects*; D009496:Neurotensin / Q000494:pharmacology*; D009543:Nifedipine / Q000494:pharmacology; D011720:Pyrazoles / Q000494:pharmacology; D011804:Quinolines / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D018028:Receptors, Neurotensin / Q000037:antagonists & inhibitors
chemical_list: D002120:Calcium Channel Agonists; D002121:Calcium Channel Blockers; D018679:Cholinergic Agonists; D018680:Cholinergic Antagonists; D011720:Pyrazoles; D011804:Quinolines; D018028:Receptors, Neurotensin; D018723:Bethanechol; C079087:SR 48692; D001030:Apamin; D009496:Neurotensin; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D001285:Atropine; D009543:Nifedipine; D002118:Calcium