[Influence of pH and calcium of the environment on the electrical activity of an isolated muscle spindle].

The effects of external pH and Ca concentration were studied as applied to the receptor potential and impulse response of isolated frog muscle spindles. With a decrease in pH the amplitude and duration of the hyperpolarizing phase of the receptor potential increased, and the amplitude of the depolarizing phase decreased. The background firing anc evoked impulse activity decreased. An increase in pH decreased the amplitude and duration of the hyperpolarizing phase of the receptor potential; The background firing initially grew, then decreased up to 30-50 per cent of the standard. An increase in external Ca concentration increased the background firing in an alkaline medium and reduced the firing when pH was neutral or acid. The results are discussed in connection with possible alterations in the rate of the active (electrogenic) and passive transport of the Na and Ca ions