Facilitation of shock-induced fighting following intraventricular 5,7-dihydroxytryptamine and 6-hydroxydopa.

Using a 15-s intershock interval, an increase in shock-induced fighting was observed following intraventricular 96 microgram 5,7-dihydroxytryptamine (5,7-DHT) and 90 microgram 6-hydroxydopa (6-OHdopa). The incidence of predatory mouse killing was enhanced by 5,7-DHT, but was not affected by 6-OHdopa. Pain sensitivity was increased by 6-OHdopa, but both neurotoxins produced hyperreactivity to footshock. Specific serotonin depletion was produced by 5,7-DHT and norepinephrine depletion by 6-OHdopa. The increase in shock-induced fighting could not be predicted on the basis of monoamine depletion alone, since a long intershock interval was necessary to observe this increase.