Acute ethanol alters calcium signals elicited by glutamate receptor agonists and K+ depolarization in cultured cerebellar Purkinje neurons

The effect of acute ethanol on Ca2+ signals evoked by ionotropic (iGluR) and metabotropic (mGluR) glutamate receptor (GluR) activation and K+ depolarization was examined in cultured rat cerebellar Purkinje neurons to assess the ethanol sensitivity of these Ca2+ signaling pathways. Mature Purkinje neurons similar to 3 weeks in vitro were studied. iGluRs were activated by (RS)-alpha-amino-3-hydroxyl-5 methyl-4-isoxazolepropionic acid (AMPA; 1 and 5 mu M) and domoate (5 mu M) mGluRs were activated by (1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid (ACPD; 300 mu M) and (R,S)-3,5-dihydroxyphenylglycine (DHPG; 200 mu M) These agents and K+ (150 mM) were applied from micropipettes by brief (1 s) microperfusion pulses. Ca2+ levels were monitored at 2-3 s intervals during pre-and post-stimulus periods using microscopic digital imaging and the Ca2+ sensitive dye fura-2. iGluR and mGluR agonists and K+ produced abrupt increases in intracellular Ca2+ that slowly recovered to baseline resting levels. Acute exposure to ethanol at 33 mM (150 mg%) and 66 mM (300 mg%) significantly reduced the amplitude of the Ca2+ signals to iGluR agonists and K+ with little or no effect on Ca2+ signals to mGluR agonists. In contrast, acute ethanol at 10 mM (45 mg%) had no effect on the Ca2+ signals to the iGluR agonist AMPA but significantly enhanced the Ca2+ signals to the mGluR agonist DHPG. These results show that ethanol modulates Ca2+ signaling linked to GluR activation in a receptor subtype specific manner, and suggest that Ca2+ signaling pathways linked to GluR activation and membrane depolarization may be important mechanisms by which ethanol alters the transduction of excitatory synaptic signals at glutamatergic synapses and thereby affects intercellular and intracellular communication in the CNS. (C) 1997 Elsevier Science B.V.