LOW AND MODERATE DOSES OF ETHANOL PRODUCE DISTINCT PATTERNS OF CEREBRAL METABOLIC CHANGES IN RATS

The quantitative autoradiographic 2-[C-14]deoxyglucose method was used to measure the effects of the acute administration of ethanol on loca l rates of glucose utilization in male Sprague-Dawley rats. Rates of g lucose utilization were measured 10 min after the intraperitoneal admi nistration of 0.00, 0.25, 0.50, and 1.00 g/kg ethanol. The acute admin istration of the lowest dose of ethanol (0.25 g/kg) significantly incr eased rates of cerebral metabolism, as compared with vehicle-treated c ontrols, in structures of the mesocorticolimbic and nigrostriatal dopa minergic systems. Among the affected regions were the nucleus accumben s, medial prefrontal cortex, olfactory tubercle, caudate, ventral tegm ental area, and substantia nigra. Acute administration of 0.50 g/kg et hanol resulted in similar trends in increased functional activity; how ever, significant increases were limited to the somatosensory cortex, posterior nucleus accumbens, and the CA3 region of the hippocampus. In contrast, the administration of 1.00 g/kg ethanol produced widespread decreases in rates of glucose utilization in brain regions involved i n processing of sensory and motor information, as well as in portions of the limbic system. These data indicate that the effects of acute et hanol administration on functional activity as reflected by rates of g lucose utilization are dose-dependent. These cerebral metabolic effect s parallel the dose dependent effects of ethanol on motor behavior, wi th stimulatory effects generally observed at lower doses and depressiv e effects at higher doses. Moreover, each of the doses studied produce d alterations in functional activity in a unique subset of structures. This suggests that different neuroanatomical circuits mediate the eff ects of each dose.