[Roles of noradrenergic and dopaminergic systems in the self-stimulation behavior of the substantia nigra].

A bipolar electrode was stereotaxically implanted in the substantia nigra of male albino Wistar-Imamichi rats. 1) Rats lifted and turned their heads and contralateral forelimb towards the contralateral side to the electrode during the substantia nigral self-stimulation (SS) behavior. 2) Methamphetamine facilitated the SS dose-dependently in the "threshold"-intensity reinforcement. The pretreatment of imipramine facilitated the effects of methamphetamine. 3) FLA63 and U-14,624, dopamine beta-hydroxylase inhibitors, suppressed the SS in the moderate-intensity reinforcement. 4) Apomorphine, stimulant of dopamine receptor, did not facilitate, but rather inhibited the SS dose-dependently in the "threshold"-intensity reinforcement. 5) l-Norepinephrine injected into the lateral ventricle facilitated the SS dose-dependently. On the other hand, dopamine had no marked effects. 6) These results suggest that the noradrenergic system in the brain plays a more important role in the positive reinforcement of the substantia nigral SS behavior than does the dopaminergicsystem.