8-OH-DPAT MICROINJECTED IN THE REGION OF THE DORSAL RAPHE NUCLEUS BLOCKS AND REVERSES THE ENHANCEMENT OF FEAR CONDITIONING AND INTERFERENCEWITH ESCAPE PRODUCED BY EXPOSURE TO INESCAPABLE SHOCK

Prior work suggests that inhibition of the dorsal raphe nucleus (DRN) either during exposure to inescapable electric shock (IS) or during la ter behavioral testing might block the usual behavioral consequences o f IS. The 5-HT1A agonist 8-OH-DPAT was microinjected into the region o f the DRN either before exposure to IS or before testing for fear cond itioning and escape learning conducted 24 hr later. IS potentiated fea r conditioning and interfered with escape performance. These effects w ere completely prevented by intra-DRN administration of 8-OH-DPAT at e ither point. Low but not high systemic doses of 8-OH-DPAT had a simila r effect, supporting the idea that the effective site of action is pre synaptic. The relation between these data and other effects of 8-OH-DP AT is discussed.