Positive and negative inotropic effects of carbachol on the embryonic chick atrium |
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| Authors: | L L Protas |
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| Institution: | (1) Sechenoy Institute of Evolutionary Physiology and Biochemistry, USSR Academy of Sciences, M. Torez 44, 194223 St. Petersburg, (USSR);(2) Present address: 154 Harvard Street, apt. 1, 02146 Brookline, MA, USA |
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| Abstract: | The effect of carbachol on twitch tension of atrial preparations from chick embryos of different incubation ages (3–14 days) was studied. At every age carbachol evoked negative (at low concentrations) and positive (at higher concentrations) inotropic responses. Maximal response values for both effects increased with age; in 3- and 5-day atria the positive inotropic response prevailed. The muscarinic antagonist pirenzepine inhibited the positive (on 5-day atria) and negative (on strips of 14-day atria) inotropic effects of carbachol with pA2 values of 6.8 and 8.0, respectively, suggesting that muscarinic receptors mediating these effects belong to different receptor subtypes. |
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| Keywords: | Carbachol pirenzepine muscarinic inotropism atrium chick embryo |
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