Effects of dopamine-receptor blockade on self-stimulation in the monkey.

In a dose-response experiment it was shown that intraperitoneal injections of 0.062 mg/kg, and 0.1 mg/kg of the dopamine-receptor blocking agent and neuroleptic spiroperidol severely attenuate self-stimulation in the orbitofrontal cortex, hypothalamus, and in the region of the locus coeruleus, in the rhesus monkey and in the squirrel monkey. In the rhesus monkey intracranial injections of 6 mug of spiroperidol bilaterally into the nucleus accumbens or the hypothalamus attenuated self-stimulation of the amygdala, and injections into the orbitofrontal cortex attenuated self-stimulation of the amygdala and lateral hypothalamus. Self-stimulation at other sites tested (including the region of the locus coeruleus) was much less affected by the injections, and injections into the region of the locus coeruleus were ineffective. These results together with other control experiments suggest that spiroperidol can attenuate self-stimulation in the monkey independently of any motor impairment or sedation produced, and that dopamine receptors in particular brain regions are involved in self-stimulation of particular brain sites.