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XB-ART-4062
J Physiol 2004 Apr 01;556Pt 1:121-34. doi: 10.1113/jphysiol.2003.056168.
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Intracellular Na+ inhibits voltage-dependent N-type Ca2+ channels by a G protein betagamma subunit-dependent mechanism.

Blumenstein Y , Maximyuk OP , Lozovaya N , Yatsenko NM , Kanevsky N , Krishtal O , Dascal N .


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N-type voltage-dependent Ca(2+) channels (N-VDCCs) play important roles in neurotransmitter release and certain postsynaptic phenomena. These channels are modulated by a number of intracellular factors, notably by Gbetagamma subunits of G proteins, which inhibit N-VDCCs in a voltage-dependent (VD) manner. Here we show that an increase in intracellular Na(+) concentration inhibits N-VDCCs in hippocampal pyramidal neurones and in Xenopus oocytes. In acutely dissociated hippocampal neurones, Ba(2+) current via N-VDCCs was inhibited by Na(+) influx caused by the activation of NMDA receptor channels. In Xenopus oocytes expressing N-VDCCs, Ba(2+) currents were inhibited by Na(+) influx and enhanced by depletion of Na(+), after incubation in a Na(+)-free extracellular solution. The Na(+)-induced inhibition was accompanied by the development of VD facilitation, a hallmark of a Gbetagamma-dependent process. Na(+)-induced regulation of N-VDCCs is Gbetagamma dependent, as suggested by the blocking of Na(+) effects by Gbetagamma scavengers and by excess Gbetagamma, and may be mediated by the Na(+)-induced dissociation of Galphabetagamma heterotrimers. N-VDCCs may be novel effectors of Na(+)ion, regulated by the Na(+) concentration via Gbetagamma.

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References [+] :
Bean, Neurotransmitter inhibition of neuronal calcium currents by changes in channel voltage dependence. 1989, Pubmed