Effects of microiontophoretic application of cocaine, alone and with receptor antagonists, upon the neurons of the medial prefrontal cortex, nucleus accumbens and caudate nucleus of rats.

The spontaneous extracellular electrical activity of 102 neurons, within the caudate nucleus (CN), medial prefrontal cortex (MPC), nucleus accumbens (NAc) and a control site, the lateral thalamic nucleus (LT), was studied. Cocaine depressed spontaneous activity in the majority of the cells studied from all regions except the lateral thalamus. Desipramine, which has been used clinically for the treatment of withdrawal of cocaine, also depressed neuronal activity in the caudate nucleus. In addition, of the three receptor antagonists tested, sulpiride, methysergide and naloxone, only the dopamine antagonist (sulpiride) affected cocaine-induced neuronal responses. This study further emphasizes the emerging importance of midbrain dopaminergic systems in the pharmacological effects of this important drug of abuse.