Contractures produced by carbamate anticholinesterases in bovine tracheal smooth muscle.
1. In isolated strips of bovine tracheal muscle the carbamate anticholinesterases, neostigmine and eserine caused similar, slowly-developing, sustained spasms which were concentration-related in the range 10(-7)-10(-4) mol/l; these spasms could be abolished either by withdrawing the anticholinesterase or by addition of atropine (5 X 10(-7) mol/l). 2. Depletion of tissue stores of acetylcholine using hemicholinium-3 with or without electrical stimulation rendered the muscle unresponsive to neostigmine (10(-6) mol/l). Responses to acetylcholine itself were not impaired. 3. A low concentration of neostigmine (10(-8) mol/l) did not cause spasm but enhanced the contractile response of bovine trachealis to acetylcholine, carbachol and histamine. This concentration of neostigmine also increased the muscle's contraction upon exposure to a high-potassium solution, even in the presence of atropine (5 X 10(-7) mol/l). 4. It is concluded that neostigmine and eserine cause spasm not only by preventing breakdown of endogenously released acetylcholine but also by stimulating release of acetylcholine from nerve terminals and by a non-specific enhancement of muscle contraction.
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D002217:Carbachol / Q000494:pharmacology; D002219:Carbamates / Q000494:pharmacology*; D002417:Cattle; D002800:Cholinesterase Inhibitors / Q000494:pharmacology*; D006632:Histamine / Q000494:pharmacology; D066298:In Vitro Techniques; D009119:Muscle Contraction / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects*; D009388:Neostigmine / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D014132:Trachea / Q000187:drug effects*
D002219:Carbamates; D002800:Cholinesterase Inhibitors; D009388:Neostigmine; D006632:Histamine; D002217:Carbachol; D000109:Acetylcholine; D011188:Potassium