Influence of cocaine administration patterns on dopamine receptor regulation.

Chronic exposure to drugs of abuse induces important modifications on neuronal systems. Increasing evidence shows that the consequences to chronic cocaine exposure can be different depending on the administration pattern. The aim of the present study was to evaluate the consequences of two cocaine administration patterns on dopaminergic receptor regulation. Male Sprague-Dawley rats were injected with cocaine (20 mg/kg, i.p.) for 14 days according to an intermittent (one daily injection) or a binge (three daily injections) pattern. By autoradiography, we compared the modifications of dopamine D1 and D2 receptor densities in the dopaminergic systems (mesocorticolimbic and nigrostriatal) 1 (WD1) and 14 (WD14) days after the last cocaine injection. On WD1, we observed modifications of D1 receptors after the binge cocaine treatment pattern while no modification was observed after the intermittent pattern, suggesting that multiple daily injections are needed to induce early D1 receptor modifications. On the contrary, densities of the D2 receptors were modified by both cocaine administration patterns, and interestingly, they were opposite depending on the administration pattern. On WD14, we observed different modifications of D1 and D2 receptors depending on the administration pattern, suggesting that the cocaine administration pattern promoted long-term regulations of the dopaminergic system. Two cocaine administration patterns induce different modifications of the dopaminergic receptor densities.