METABOLIC MAPPING OF THE EFFECTS OF ORAL ALCOHOL SELF-ADMINISTRATION IN RATS

The functional effects of the voluntary consumption of ethanol in rats were investigated using the quantitative autoradiographic 2-[C-14]deo xyglucose method for measurement of rates of local cerebral glucose ut ilization, A modified sucrose-substitution procedure was used to train three groups of Wistar rats to self-administer water, a 5% sucrose so lution, or a 10% ethanol/5% sucrose solution in daily sessions. Once s table rates of consumption were established, the 2-[C-14]deoxyglucose method was applied immediately after completion of the final test sess ion, Rats received a dose of ethanol equivalent to 0.5 g/kg (n = 6) on the day of the procedure or a comparable volume of sucrose solution ( n = 6) or water (n = 5). Rates of local cerebral glucose utilization i n rats that ingested water did not differ from those that rats consume d a 5% sucrose solution. In contrast, voluntary ethanol consumption pr oduced a highly discrete pattern of changes in rates of glucose utiliz ation. Ethanol ingestion increased cerebral metabolism, as compared wi th rates of metabolism in rats that consumed either water or sucrose i n the rostral pole and shell of the nucleus accumbens, medial prefront al cortex, lateral septum, basolateral and central nuclei of the amygd ala, substantia nigra, and the ventral tegmental area. This pattern of alterations in functional activity is distinctly different from that observed when equivalent doses of ethanol are administered acutely, em phasizing the importance of self-administration in determining the cha nges in glucose utilization, Furthermore, within the nucleus accumbens , glucose utilization was selectively augmented in the rostral pole an d shell subterritories, whereas cerebral metabolism in the core was un affected. Finally, these data demonstrate that it is the simultaneous activation of an interconnected network of limbic brain regions that s erves as the substrate of the effects of voluntarily ingested ethanol.