Changes in the substantia nigral self-stimulation behavior by intraventricular injection of norepinephrine, dopamine and GABA.

Abstract

A bipolar electrode was stereotaxically implanted in the substantia nigra of male albino Wistar-Imamichi rats. Effects of l-norepinephrine(NE), dopamine(DA) and γ-aminobutyric acid (GABA), injected into the lateral ventricle, on the substantia nigral self-stimulation(SS) behavior, and the effects of α- and β-adrenergic receptor antagonists on the facilitation induced by NE were investigated. NE but not DA facilitated the SS behavior and GAGA showed no constant effects on the behavior. Facilitation by NE of SS behavior was inhibited by phentolamine, but not by propranolol. These results suggest that the noradrenergic system in the brain may play a more significant role in the positive reinforcement of the substantia nigral SS behavior than does the dopaminergic or GABA-ergic system, and that the action of NE may be facilitated through α-receptors rather than through β-receptors.