Effects on hypothalamic self-stimulation of drugs influencing dopaminergic neurotransmission injected into nucleus accumbens and corpus striatum of rats.

The role of the nucleus accumbens septi (ACB) and corpus striatum (CPU) in self-stimulation were investigated by injecting directly or indirectly acting stimulant drugs or a dopamine-(DA)-receptor blocking agent into each site bilaterally. d-Amphetamine (68 nmol) facilitated hypothalamic self-stimulation when injected into either side. Apomorphine (40 nmol) depressed or facilitated responding, the direction and magnitude of this effect being contingent (C = 0.52) on the effect of systemic injection (0.3 mg/kg.i.p.), and correlated with the difference between the effects of d- and l-amphetamine (0.5 mg/kg i.p.) but not with injection site. Haloperidol (6.6 nmol) in either site depressed self-stimulation. Tyramine (730 nmol), an agent believed to cause noncontingent displacement of transmitter from catecholamine terminals, depressed self-stimulation when injection into CPU, but facilitated it when injected into ACB. The site-specific effects found with tyramine but not with apomorphine may have been due to release by tyramine of transmitters other than DA.