Haloperidol-based conditioned increase in locomotor activity is disrupted by latent inhibition and extended...

Previous research have shown that repeated administration of 0.5 mg/kg of haloperidol in a given context gives rise to an increase in activity when spontaneous locomotor activity is recorded in a drug-free test conducted in such context. In order to confirm whether this type of response is based on processes of a Pavlovian nature, we conducted two experiments involving two manipulations that disrupt conditioning in typical classical conditioning procedures: preexposure of the to-be-conditioned stimulus (latent inhibition), and an increase in the length of the inter-stimulus interval. The results revealed that both manipulations were effective in reducing the conditioned increase of the locomotor response. This kind of conditioning can be explained in terms of the differential effects of low vs. high doses of haloperidol, and the temporal dynamics of conditioned response.