Effects of dopamine receptor stimulants on locomotor activity of rats with electrolytic or 6-hydroxydopamine-induced lesions of the nucleus accumbens.

Ergometrine (8 mg/kg) injected intraperitoneally into normal rats had little effect on locomotor activity. In contrast, rats with selective 6-hydroxydopamine-induced lesions of dopamine terminals in the nucleus accumbens showed a strong stimulation of locomotor activity following injection of this dose or ergometrine. The dopamine analogue 2-amino-6-7-dihydroxy-1, 2, 3, 4-tetrahydronaphthalene (ADTN) (150 mug), caused strong and long lasting stimulation of locomotor activity when injected intracerebroventricularly into rats. The ADTN response was markedly reduced in rats with bilateral electrolytic lesions of the nucleus accumbens, but unchanged in rats with bilateral electrolytic lesions of the caudate nucleus. At a lower dose level (50 mug) ADTN, injected intracerebroventricularly, had little effect on the locomotor activity of normal or sham-operated rats. This dose of ADTN was, however, effective in causing locomotor stimulation of rats with bilateral 6-hydroxydopamine-induced lesions of the nucleus accumbens. These results support the view that the dopamine receptors in the nucleus accumbens are involved in the actions of locomotor stimulant drugs.