Apomorphine: selective inhibition of the aversive component of lateral hypothalamic self-stimulation.

The effects of dopamine agonists on self-stimulation are a matter of considerable dispute. Apomorphine has variously been reported to inhibit, have no effect on, or to facilitate lever-press self-stimulation. To investigate the possibility that these discrepancies may reflect peculiarities of the lever-press test situation, the present study investigated the effects of apomorphine on locomotor initiation of and escape from lateral hypothalamic stimulation in a shuttle-box. Apomorphine had relatively little effect on the initiation behavior, but it produced a large and dose-dependent inhibition of escape. These data suggest that apomorphine acts to inhibit the aversive component of lateral hypothalamic stimulation. The implications of these findings for the usefulness of the shuttle-box in investigating the pharmacology of self-stimulation are discussed.