Effects of TRH, ethanol, and TRH-ethanol combination on activity in rats with altered monoamine content.

Investigations were undertaken with 5,7-dihydroxytryptamine and 6-hydroxydopamine treated rats to see whether activity changes induced by TRH, ethanol and the TRH-ethanol combination would be affected after reduced monoamine function. In keeping with earlier results, TRH increased activity, ethanol reduced activity and the TRH-ethanol combination produced activity counts greater than those for TRH alone. Neither the 5,7-dihydroxytryptamine-induced reduction of brain serotonin nor the 6-hydroxydopamine treatments which reduced brain catecholamines altered the hyperactivity induced by TRH or the TRH-ethanol combination. While reduction of brain serotonin did not affect the ethanol-induced changes in activity, preferential reduction of dopamine as well as reduction of both norepinephrine and dopamine significantly antagonized this measure of ethanol-induced depression. The reduction of dopamine alone produced the greatest effect on this action of ethanol. It can be concluded from the data that the increased locomotion induced by TRH and the TRH-ethanol combination does not depend upon endogenous monoamines, whereas the sedative effects of ethanol are apparently influenced by alterations in brain catecholamine function.