ABSTRACT
The dopamine D1 receptor is centrally involved in mediating the effects of cocaine and is essential for cocaine-induced locomotor sensitization. Changes in D1 receptor expression have been reported in various models of cocaine addiction; however, the mechanisms that mediate these changes in D1 receptor expression are not well understood. Using preadolescent drd1a-EGFP mice and a binge cocaine treatment protocol we demonstrate that the D1 receptor is post-transcriptionally regulated in the caudate-putamen of cocaine-sensitized animal. While cocaine-sensitized mice express high levels of steady-state D1 receptor mRNA, the expression of D1 receptor protein is not elevated. We determined that the post-transcriptional regulation of D1 receptor mRNA is rapidly attenuated and D1 receptor protein levels increase within 30 min when the sensitized mice are challenged with cocaine. The rapid increase in D1 receptor protein levels requires de novo protein synthesis and correlates with the cocaine-induced hyperlocomotor activity in the cocaine-sensitized mice. The increase in D1 receptor protein levels in the caudate-putamen inversely correlated with the levels of microRNA 142-3p and 382, both of which regulate D1 receptor protein expression. The levels of these two microRNAs decreased significantly within 5 min of cocaine challenge in sensitized mice. The results provide novel insights into the previously unknown rapid kinetics of D1 receptor protein expression which occurs in a time scale that is comparable to the expression of immediate early genes. Furthermore, the results suggest a potential novel role for inherently labile microRNAs in regulating the rapid expression of D1 receptor protein in cocaine-sensitized animals.
