Self-stimulation at the lateral hypothalamus and locus coeruleus after specific unilateral lesions of the dopamine system.

A group of rats was trained to press levers for electrical stimulation from bipolar electrodes aimed at the lateral hypothalamus (LH), and another group was trained to self-stimulate from electrodes in the locus coeruleus (LC). All rats in both groups were subjected to unilateral injections of 6-hydroxydopamine into the substantia nigra and midbrain ventral tegmentum. The lesions produced profound depletions of dopamine from the ipsilateral frontal cortex, nucleus accumbens/olfactory tubercle, and corpus striatum. Pretreatment with desmethylimipramine prevented loss of noradrenaline in excess of that caused by electrode implantation. The destruction of the dopamine projections produced a persistent and pronounced deficit in intracranial self-stimulation from ipsilateral electrodes in both the LH and LC groups, but only transient effects on self-stimulation from contralateral electrodes at these sites. These results suggest that an intact dopamine system is required for the expression of self-stimulation behaviour.