[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.

[Cooperative effect of calcium ions in freeing a mediator from the neuromuscular synapses of large and small muscle fibers of frog sartorius muscle].

The dependence of a amplitude and quantum content (m) of the end plate potentials on the external calcium concentration was studied in experiments on the frog sartorius amplitude of the miniature end plate potentials were found. The data obtained suggest that the number of calcium ions taking part in the release of each transmitter quantum may be different.