[Effect of beta-endorphin on the development of denervation changes in the membrane of the muscle fiber in the rat].

A decrease in the resting membrane potential, an increase in the input resistance, appearance of the anode breakdown and tetrodotoxin-resistant action potentials and extrajunctional acetylcholine sensitivity following denervation were revealed in surviving rat diaphragm muscle fibres. Addition of beta-endorphin (1.10(-8) M) to the culture medium prevented on increase in the input resistance and reduced a degree of the extrajunctional acetylcholine sensitivity, but did not inhibit the appearance of the anode breakdown and tetrodotoxin-resistant action potentials. Naloxone (1.25.10(-6) M) did not avert the effect of beta-endorphin, more over it exerted a beta-endorphin-like effect on the denervated muscle fibres. It is suggested that beta-endorphin can be the factor which is responsible for the neurotrophic control of passive electrical properties of the muscle fibre membrane and neurotrophic regulation of the membrane sensitivity to acetylcholine.