Abstract
Properties of the excitable sites in the squid axon membrane were studied by using various chemical stimulants and a real-time spectrum analyzer. Intact squid axons immersed in media with a reduced divalent cation concentration develop very small electric responses (1-30μV in amplitude) which repeat at more-or-less regular intervals. The frequency of repetition of these miniature responses falls when the temperature of the axon is lowered. Replacement of a small fraction of the external Na-ion with K-ion is a powerful means of generating miniature responses. Passage of an outwardly directed current through the axonal membrane also evokes miniature responses. This effect of an electric current is attributed to a transport of intracellular K-ion into the axonal membrane. The results of the effects of external application of the salts of Li-, Rb-and Cs-ion indicate that the ability of alkali metal ions to induce miniature response falls in the following order: K, Rb>Cs>Na>Li.
