The effect of microinjections of amphetamine into the neostriatum and the nucleus accumbens on self-stimulation behaviour.

The effect of micro-injections of dexamphetamine chloride into the neostriatum, the nucleus accumbens, the anterior hypothalamus, and the ventricular system on self-stimulation with electrodes in the ventral tegmentum was studied. Unilateral injections of 10 mug into the anterior hypothalamus produced no effect. Injections into the neostriatum tended to depress the self-stimulation rate, whereas injections into the nucleus accumbens increased the rate markedly. Bilateral injections (2 times 2.5 mug and 2 times 5 mug amph.) into the nucleus accumbens were more effective than unilateral injections and were as effective as systemic injections of 1 mg/kg amphetamine (i.p.). Bilateral injections into the neostriatum also increased the self-stimulation rate. Injections of 10 mug into the ventricular system resulted in a smaller increase which was not statistically significant. These results are discussed in relation to the involvement of the dopaminergic system in the maintenance of self-stimulation behaviour.