Concanavalin A blocks the Ca2+ -dependence of crayfish muscle fiber responses to glutamate.
(1) The response of crayfish muscle fibers to bath-applied glutamate is strongly inhibited when the Ca concentration of the physiological solution is reduced. Other divalent cations cannot substitute for Ca. The trivalent impermeant cation La can at low concentration replace Ca. Moreover, decreasing the Ca concentration in the presence of La potentiates the glutamate response. (2) The time course of responses to ionophoretically applied glutamate suggests a faster desensitization in low Ca solutions. The lectin concanavalin A, which blocks desensitization, also eliminates the decrease of the glutamate response in low Ca solutions. (3) The above results are compared to available data concerning Ca-dependence, desensitization and effects of concanavalin A.
D000818:Animals; D003400:Astacoidea; D002118:Calcium / Q000494:pharmacology*; D002413:Cations, Divalent; D003208:Concanavalin A / Q000494:pharmacology*; D005971:Glutamates / Q000494:pharmacology*; D018698:Glutamic Acid; D009132:Muscles / Q000187:drug effects / Q000502:physiology*
D002413:Cations, Divalent; D005971:Glutamates; D003208:Concanavalin A; D018698:Glutamic Acid; D002118:Calcium