EFFECTS OF COCAINE AND GBR-12909 ON BRAIN-STIMULATION REWARD

Cocaine and GBR-12909, two dopamine reuptake blockers, were administer ed in a multiple current rate-frequency curve-shift test of intracrani al self-stimulation (ICSS) reward in rats with medial forebrain bundle (MFB) electrodes. Acute injections of cocaine (0, 5, 15, 30 mg/kg, IP ) increased ICSS reward at all currents (501, 316, 200 mu Amps) as mea sured by decrease half-maximal frequency threshold. Cocaine also incre ased operant motor performance but only at the low current. In additio n, cocaine increased dynamic interval at the highest dose at all curre nts. Similar treatment with GBR-12909 (0, 5, 10, 20 mg/kg, IP) signifi cantly increased ICSS reward (decreased threshold) especially at the m edium dose in all currents and had no significant effects on operant m otor performance or dynamic interval. The major novel finding of the p resent study is that the rewarding effects of both drugs was not depen dent on the choice of stimulation current, which is discussed as simpl ifying future psychophysical testing of psychostimulant drugs in the I CSS rate-frequency curve-shift paradigm.