Interaction of serotonin- and dopaminergic systems of the brain in mechanisms of latent inhibition in rats.

The activity of serotoninergic neurons of the medial raphé nucleus was turned off by local injection of the neurotoxin, 5,7-dihydroxytryptamine. Seven days later, a conditioned passive avoidance reaction was developed following 20 preexposures to the conditional stimulus (the presentation of the experimental chamber). As compared with the sham-operated control, in which 20 preexposures to the stimulus elicited latent inhibition, i.