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  • Title: Calcium-independent desensitization of rises in intracellular free Ca2+ concentration and catecholamine release in cultured adrenal chromaffin cells.
    Author: Sasakawa N, Ishii K, Kato R.
    Journal: Biochem Biophys Res Commun; 1985 Nov 27; 133(1):147-53. PubMed ID: 2416315.
    Abstract:
    Exposure of adrenal chromaffin cells to carbamylcholine (CCh) in the absence of extracellular Ca2+ suppressed rises in intracellular free Ca2+ concentration ([Ca2+]i) induced by subsequent addition of Ca2+ into the incubation medium. The extent of the suppression was dependent on the concentration of CCh and the duration of exposure. A similar inhibitory effect of CCh was also observed in the case of catecholamine release. In contrast, pretreatment with 56 mM K+ did not affect these two responses induced by Ca2+. Recovery from the desensitized state was rapid, since the responses became normal within 3 min following washout of the maximum concentration of CCh. These results show that, in Ca2+-free medium, exposure of the cells to CCh induces desensitization as indicated by diminished rise in [Ca2+]i and reduced release of catecholamines. These phenomena were not due to direct inhibition of voltage-dependent Ca2+ channels by CCh, but seem to be due to an uncoupling of signal transduction between the nicotinic receptor and Ca2+ channel.
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