title: Action of tacrine on muscarinic receptors in rat intestinal smooth muscle.
abstract: 1. The reversible cholinesterase inhibitor, tacrine (THA) was examined against the contractions of rat duodenum to acetylcholine and carbachol (cholinesterase resistant). 2. Tacrine (10(-6) M) showed a similar behaviour to physostigmine (10(-6) M), changing the characters of the concentration-response curve to Ach. The contractual responses were shifted to the left at low concentrations of ACh to reveal a bell-shaped curve with declaring contradictions at high concentrations of ACh. 3. Antagonism by atropine (10(-8) M) was reduced in the presence of tacrine (10.54, dose-ratio) compared with the shift of the curve in the absence of tacrine (73.9, dose-ratio). The declining phase of the concentration-response curve to ACh was also antagonized by atropine. 4. Further evidence for muscarininc receptor antagonism by tacrine was a small rightward shift of the concentration-response curve for carbachol, an agonist immune to cholinesterase. 5. This study has shown that tacrine acts both as a cholinesterase inhibitor and muscarinic antagonist on rat intestinal smooth muscle.
authors.affiliation: Departamento de Farmacología, Facultad de Farmacia, Universidad de Sevilla, Profesor García-Gonzalez s/n, 41012 Sevilla, Spain.
authors.forename: M A
authors.initials: MA
authors.lastname: Becerra
authors.forename: M D
authors.initials: MD
authors.lastname: Herrera
authors.forename: E
authors.initials: E
authors.lastname: Marhuenda
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D002217:Carbachol / Q000494:pharmacology; D002800:Cholinesterase Inhibitors / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004386:Duodenum / Q000187:drug effects; D005260:Female; D066298:In Vitro Techniques; D007422:Intestines / Q000187:drug effects*; D008297:Male; D018727:Muscarinic Antagonists / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects*; D051381:Rats; D017208:Rats, Wistar; D011976:Receptors, Muscarinic / Q000187:drug effects*; D013619:Tacrine / Q000494:pharmacology*
chemical_list: D002800:Cholinesterase Inhibitors; D018727:Muscarinic Antagonists; D011976:Receptors, Muscarinic; D013619:Tacrine; D002217:Carbachol; D000109:Acetylcholine