Evidence for site specific ethanol actions in the CNS.

The diverse behavioral and biochemical effects induced by ethanol suggest that ethanol exerts differential effects on the CNS. When the neuroactive amino acids, glycine, glutamate, aspartate, GABA and taurine, were measured in the cortex, striatum, hippocampus, midbrain, and brain stem of acute or chronic ethanol-treated rats, site specific changes were observed for glutamate, glycine, and aspartate. No changes were found for GABA or taurine. Upon in vivo application, it was found that the microinjection of thyrotropin-releasing hormone (TRH, 500 ng) into the medial septum significantly shortened ethanol's impairment of the righting reflex, while microinjection of muscimol (30 ng) markedly potentiated ethanol's impairment of the righting reflex. When these studies are combined with previous work showing that microinjection of muscimol (30 ng) into the inferior colliculus blocks audiogenically induced seizures in ethanol-withdrawn rats, the convergence implies that specific sites in the CNS may modulate certain actions of ethanol. Therefore, we propose that the medial septum and inferior colliculus can be used as in vivo models to study the acute and chronic actions of ethanol, respectively.