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

Abstract

The effect of acute ethanol on Ca 2+ 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 Ca 2+ signaling pathways. Mature Purkinje neurons ∼3 weeks in vitro were studied. iGluRs were activated by ( RS)-α-amino-3-hydroxyl-5 methyl-4-isoxazolepropionic acid (AMPA; 1 and 5 μM) and domoate (5 μM). mGluRs were activated by (1 S,3 R)-1-aminocyclopentane-1,3-dicarboxylic acid (ACPD; 300 μM) and ( R, S)-3,5-dihydroxyphenylglycine (DHPG; 200 μM). These agents and K + (150 mM) were applied from micropipettes by brief (1 s) microperfusion pulses. Ca 2+ levels were monitored at 2–3 s intervals during pre- and post-stimulus periods using microscopic digital imaging and the Ca 2+ sensitive dye fura-2. iGluR and mGluR agonists and K + produced abrupt increases in intracellular Ca 2+ 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 Ca 2+ signals to iGluR agonists and K + with little or no effect on Ca 2+ signals to mGluR agonists. In contrast, acute ethanol at 10 mM (45 mg%) had no effect on the Ca 2+ signals to the iGluR agonist AMPA but significantly enhanced the Ca 2+ signals to the mGluR agonist DHPG. These results show that ethanol modulates Ca 2+ signaling linked to GluR activation in a receptor subtype specific manner, and suggest that Ca 2+ 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.