Tolerance to inhibition by ethanol of N-methyl-D-aspartate-induced depolarization in rat locus coeruleus neurons in vitro.

Intracellular recordings were made in a pontine slice preparation of the rat brain containing the nucleus locus coeruleus. The pressure application of N-methyl-D-aspartate (NMDA) produced reproducible depolarizations of stable amplitude. Superfusion with ethanol (100 mM) for 15 min inhibited the depolarizing response to NMDA: the effect of ethanol was rapidly reversed on washout. When the superfusion time of ethanol (100 mM) was increased to 60 min, its inhibitory effect disappeared after 50 to 60 min. Moreover, after the subsequent washout of ethanol a withdrawal-like increase in the sensitivity to NMDA became evident. Hence, adaptive mechanisms of locus coeruleus neurons during the long-time contact with ethanol may be modelled in an in vitro system.