title: Properties of excitable sites in the squid axon membrane as revealed by use of chemical stimulants and a spectrum analyzer.
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 (1-30 micronV 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 is greater than Cs is greater than Na is greater than Li.
mesh_terms: D000818:Animals; D001369:Axons / Q000187:drug effects / Q000502:physiology*; D002586:Cesium / Q000494:pharmacology; D049832:Decapodiformes; D005071:Evoked Potentials; D066298:In Vitro Techniques; D008094:Lithium / Q000494:pharmacology; D008564:Membrane Potentials; D008722:Methods; D011188:Potassium / Q000494:pharmacology; D011343:Procaine / Q000494:pharmacology; D012413:Rubidium / Q000494:pharmacology; D013696:Temperature
chemical_list: D002586:Cesium; D011343:Procaine; D008094:Lithium; D012413:Rubidium; D011188:Potassium