Brain monoamines and free choice ethanol consumption in rats.

Rats given intraventricular (i.v.t.) injections of 6-hydroxydopa (90 microgran) showed reduced brain part noradrenaline levels but no change in free choice ethanol consumption, while rats given 6-hydroxydopamine (250 microgram) i.v.t. injections showed reduced brain part noradrenaline and dopamine levels and a reduced free choice ethanol intake. Rats given i.v.t. injections of 5,6-dihydroxytryptamine (50 microgram) showed a reduction of serotonin in the hippocampus and an increase in free choice ethanol consumption. Chronic forced ethanol consumption, achieved by placing rats on a Metrecal--ethanol diet, also increased subsequent free choice ethanol intake, but had no permanent effect on brain part monoamine levels. Rats exposed to ethanol prenatally were hyperactive at 5 weeks of age but not at 10 weeks. At 15 weeks, their ethanol preference was not different from that of controls nor did their brain part monoamine levels differ from those of controls at 16 weeks. These results indicate that disrupting the balance between the monoamine neuro-transmitter systems with the neurotoxins alters the free choice ethanol consumption of rats but that prior chronic exposure to ethanol also changes free choice ethanol consumption in the absence of any permanent change in monoamine levels. The long-term behavioral changes seen in rats exposed to ethanol are not due to permanent alterations in the brain levels of noradrenaline, dopamine, or serotonin.