BEHAVIORAL AND BIOCHEMICAL EFFECTS OF THE DOPAMINE D-3 RECEPTOR-SELECTIVE LIGAND, 7-OH-DPAT, IN THE NORMAL AND THE RESERPINE-TREATED RAT

In normal rats, the dopamine D-3 receptor-selective ligand, 7-hydroxy-2-(di-n-propylamino)tetralin (7-OH-DPAT), produced biphasic effects on spontaneous locomotor activity, i.e. suppression at low doses (0.06-0.25 mu mol kg(-1) s.c.), followed by a gradual increase in motor activity (1.0-4.0 mu mol kg(-1)). The core temperature was decreased at these latter high doses only. The reserpine-induced (8.2 mu mol kg(-1) s.c.) increase in neostriatal 3,4-dihydroxyphenylatanine (DOPA) accumulation, following treatment with m-hydroxybenzylhydrazine-(NSD-1015) (475 mu mol kg(-1) i.p.), was dos e dependently ant agonized by 7-OH-DPAT in the dose range 0.02-4.0 mu mol kg(-1). The reserpine-induced suppression of spontaneous locomotor activity, however, was antagonized at higher doses only (1.0-4.0 mu mol kg(-1)). Finally, there were no region-selective effects of 7-OH-DPAT on DOPA accumulation in the neostriatum. Thus, it appears that the dopamine D-3 receptor-preferring ligand, 7-OH-DPAT, displays the profile of a dopamine D-2 receptor agonist, pre- and postsynaptically.