Enhanced suppression of a conditioned avoidance response by haloperidol but not phenoxybenzamine in rats with bilateral parafascicular lesions.

Male rats were subject to bilateral lesions in the parafascicular nucleus (PF) of the thalamus. The lesions had little or no effect on the performance of a pre-operatively acquired conditioned avoidance response. However, the PF lesioned animals displayed an enhanced response to the dopamine receptor blocking agents haloperidol or pimozide but not to the noradrenaline receptor blocking agent phenoxybenzamine. The results indicate that intralaminar thalamic nuclei and dopaminergic extrapyramidal motor pathways are functionally connected.