The effects of a serotoninergic substrate of the nucleus accumbens on latent inhibition.

Latent inhibition is an effect consisting of a delay in the acquisition of a stimulus in response to quenching of its significance by repeated presentation (pre-exposure) before combination with the reinforcement. This phenomenon is used for studies of the mechanisms of attention. Experiments were performed on rats to determine whether latent inhibition could be formed in a passive avoidance response in conditions of blockade of serotoninergic terminals in the nucleus accumbens. After pre-exposure, sham-operated animals demonstrated a delay in acquisition of the stimulus as compared with animals not subjected to pre-exposure. Bilateral injection of the neurotoxin 5,7-dihydroxytryptamine into the nucleus accumbens led to disruption of latent inhibition, which could in turn be prevented by systemic administration of haloperidol before training. The importance of serotoninergic terminals in the nucleus accumbens for latent inhibition is discussed, along with the mechanism of their interaction with the dopaminergic system during the formation of this effect.