[Effect of hydrocortisone on the membrane properties of innervated and denervated muscle fibers in frogs].

Two injections of 10, 100 or 1000 micrograms of hydrocortisone into the lymphatic sack with one-week interval or daily injections of 100 micrograms of the hormone did not hinder a decrease in the membrane resting potential, an increase of the input resistance and time constant of the membrane as well as appearance of nonsynaptic sensitivity to acetylcholine in muscle fibers developing by the 13-15th day after denervation of the muscle. In latter two cases, however, no increase of the input resistance and time constant of the membrane occurs. Administration of the same doses of drug to intact frogs led to a decrease of the membrane resting potential, increase of the time constant and input resistance of the membrane whereas daily injections reduced the sensitivity of muscle fibers to acetylcholine. Hydrocortisone seems to be unable to hinder the postdenervation changes in the muscle membrane whereas high doses of the hormone are able to induce changes in the muscle membrane.