CONTRACTURES PRODUCED BY CARBAMATE ANTICHOLINESTERASES IN BOVINE TRACHEAL SMOOTH MUSCLE |
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Authors: | C. T. Kirkpatrick P. J. Rooney |
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Affiliation: | Physiology Department, The Queen's University of Belfast, Medical Biology Centre, Belfast, N. Ireland, UK |
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Abstract: | 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 × 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 × 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. |
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Keywords: | anticholinesterase hemicholinium-3 muscle contraction tracheal smooth muscle. |
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