The desensitization of postjunctional muscle membrane after intracellular application of membrane stabilizers and snake venom polypeptides
1972; Elsevier BV; Volume: 48; Linguagem: Inglês
10.1016/0006-8993(72)90202-8
ISSN1872-6240
Autores Tópico(s)Electrochemical Analysis and Applications
ResumoA new comparative characteristic of endplate microphysiology has been introduced. It is the feasibility of receptors to become desensitised as demonstrated on two frog species, Rana temporaria and Rana ridibunda: the decay times (τMEPC) of single quantum miniature endplate currents (MEPCs) in the sartorius muscles of both species were about 1 ms and were not affected by the desensitisation-promoting agent proadifen when AChE was active. However, when the desensitisation was induced by anticholinesterase neostigmine and promoted by proadifen, the prolongation of τMEPC from 1 ms was almost twice as great in Rana temporaria (τMEPC=4.4 ms) than in Rana ridibunda (τMEPC=3.1). This indicates that desensitisation reduces the number of available receptors and lowers the number of available ACh molecules for repetitive binding by trapping them by desensitised, high-affinity receptors significantly more in Rana ridibunda than in Rana temporaria. The application of proadifen, a promoter of desensitisation, decreased the prolongation of MEPCs in both species, but this shortening was more rapid in Rana ridibunda than in Rana temporaria. It is concluded that the desensitisation-induced reduction in the density, and the number of postsynaptic receptors is significantly higher at Rana ridibunda than in Rana temporaria endplates.
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