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Autoinhibition of transmitter release from PC12 cells and sympathetic neurons through a P2Y 12 receptor‐mediated inhibition of voltage‐gated Ca 2+ channels
Author(s) -
Lechner Stefan G.,
Dorostkar Mario M.,
Mayer Martina,
Edelbauer Hannah,
Pankevych Halyna,
Boehm Stefan
Publication year - 2004
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1111/j.1460-9568.2004.03760.x
Subject(s) - depolarization , pertussis toxin , suramin , biophysics , p2y receptor , chemistry , competitive antagonist , receptor , stimulation , membrane potential , channel blocker , synaptosome , antagonist , purinergic receptor , medicine , endocrinology , biology , g protein , biochemistry , calcium , membrane , organic chemistry
Although feedback inhibition of noradrenaline release by coreleased nucleotides is a well known phenomenon, it remained unclear which P2 receptor subtypes and associated signalling cascades may be involved. In the rat pheochromocytoma cell line PC12, 2‐methylthio‐ADP reduced noradrenaline release triggered by K + depolarization more potently than ADP and ATP, whereas UDP or UTP failed to do so. The inhibition by ADP was abolished by pertussis toxin and antagonized by reactive blue 2, 2‐methylthio‐AMP, and AR‐C69931MX, but not by suramin. AR‐C69931MX acted as a competitive antagonist with an apparent affinity of 2 n m , but did not alter noradrenaline release, when PC12 cells were continuously superfused. However, when the superfusion was halted during K + depolarization, release was significantly reduced and this inhibition was attenuated by AR‐C69931MX, thus revealing ongoing autoinhibition. Rises in cellular cyclic AMP did not alter depolarization‐evoked release nor its reduction by ADP, even though the nucleotide did inhibit cyclic AMP accumulation. ADP and the direct Ca 2+ channel blocker Cd 2+ inhibited voltage‐activated Ca 2+ currents, but not ATP‐induced currents, and both agents reduced K + ‐evoked, but not ATP‐evoked, release. Hence, if voltage‐gated Ca 2+ channels do not contribute to stimulation‐evoked release, ADP fails to exert its inhibitory action. In primary cultures of rat sympathetic neurons, ADP also reduced Ca 2+ currents and K + ‐evoked noradrenaline release, and AR‐C69931MX acted again as competitive antagonist with an apparent affinity of 3 n m . These results show that P2Y 12 receptors mediate an autoinhibition of transmitter release from PC12 cells and sympathetic neurons through an inhibition of voltage‐gated Ca 2+ channels.