CONTINUOUS EXPOSURE OF CULTURED RAT CEREBELLAR MACRONEURONS TO ETHANOL-DEPRESSED NMDA AND KCL-STIMULATED ELEVATIONS OF INTRACELLULAR CALCIUM

This series of experiments measured ethanol-induced changes in levels of free intracellular calcium. Cerebellar macroneurons, harvested from rat embryos on embryonic day 17, were cultured in the presence of 75 mM ethanol for 24, 48, or 96 hr, Intracellular calcium concentrations in control and ethanol-exposed neurons did not differ after 24 hr, but they were significantly elevated in the neurons exposed to ethanol fo r 48 or 96 hr. Similarly, increases in intracellular calcium elicited by stimulation with 50 mu M NMDA were not significantly different in c ontrol and ethanol-exposed neurons after 24 hr. After 48 and 96 hr, ho wever, NMDA-stimulated increases in intracellular calcium levels in co ntrol neurons were significantly greater than in the ethanol-exposed n eurons. These results showed that, when calcium levels were elevated b y prolonged exposure to ethanol, the neurons were significantly less r esponsive to NMDA stimulation. Increases in intracellular calcium elic ited by stimulation with 30 mM KCl were not significantly different in the control and treated neurons after 24 and 48 hr of ethanol exposur e. After 46 hr of exposure to ethanol, however, there was a significan t increase in intracellular calcium levels in control neurons followin g KCl stimulation, but not in the ethanol-exposed neurons. The fact th at neuronal responses to KCl stimulation were depressed only following 96 hr of exposure to ethanol makes it unlikely that voltage-regulated channels were the primary mediators of the ethanol-induced elevations in intracellular calcium in chronically exposed neurons.