Neurochemical correlates of brain-stimulation reward measured by ex vivo and in vivo analyses.

Evidence from ex vivo analyses of dopaminergic function following self-stimulation behavior is reviewed and compared to in vivo analyses of extracellular dopamine measured by chronoamperometry during self-stimulation. Both data bases provide strong support for a dopaminergic substrate for brain-stimulation reward obtained by electrical stimulation of the ventral tegmental area (VTA). Data obtained from in vivo measures of dopamine release are particularly compelling as a positive correlation was observed between the rate/intensity function for self-stimulation and increments in the oxidation current for dopamine. An examination of the effects of the dopamine uptake blockers, cocaine and GBR 12909 on self-stimulation and stimulated release of dopamine revealed a facilitation of both measures. In contrast, the noradrenaline uptake blocker desipramine had no effect on either self-stimulation or extracellular dopamine. These pharmacological experiments also are consistent with a dopaminergic substrate of brain-stimulation reward at electrode sites in the VTA.