THE EFFECTS OF CHRONIC COCAINE ADMINISTRATION ON BRAIN NEUROTRANSMITTER RECEPTORS

The nonmedical use of cocaine has continued to increase during the past decade, resulting in considerable interest in the clinical and neurobiological implications of this behavior. A better understanding of the complex neurobiological changes associated with chronic cocaine intoxication may assist in the search for improved methods of treatment in the clinic. In this investigation, chronic daily injections of cocaine for 15 days resulted in opposite effects on dopamine receptor number measured with [3H]sulpiride in the striatum and nucleus accumbens of rats. Binding was increased in the nucleus accumbens but decreased in the striatum. By contrast, benzodiazepine receptors measured with [3H]Ro 15‐1788 were increased in the striatum and cerebellum but decreased in the frontal cortex. Intraventricular injections of 6‐hydroxydopamine resulted in a decrease in the number of benzodiazepine receptors measured in the striatum and reduced the effects of cocaine on these receptors. These data suggest that while chronic cocaine administration may induce changes in dopaminergic activity and dopaminergic receptors, opposite effects may be observed in benzodiazepine receptor number induced either directly by cocaine or indirectly through changes in dopaminergic neuronal activity. Although the significance of these findings is not clear, the results of this investigation suggest a different noncatecholaminergicavenue for future studies to follow. Copyright © 1990 Wiley‐Liss, Inc.