Dopamine D4 receptor gene expression plays important role in extinction and reinstatement of cocaine-seeking behavior in mice.

Dopamine D4 receptor (DRD4) dysregulation is associated with a variety of behaviors including novelty-seeking, approach avoidance, and ADHD. DRD4 has also been shown to interact with the environment to produce changes in behavior and longevity. The present study sought to examine the role of DRD4 on cocaine-seeking behavior in the conditioned place preference (CPP) test and determine its effects on extinction and reinstatement in adult wild-type (WT), heterozygous (HT), and knockout (KO) mice. Results revealed that all mice, regardless of sex or genotype, developed a similar acquisition for a cocaine place preference. Female DRD4 KO mice failed to extinguish their preference for the cocaine-paired chamber following the extinction period. Male DRD4 KO mice failed to reinstate their preference after a priming dose following successful extinction. No differences in locomotor activity were observed within drug treatment conditions due to genotype, and female mice displayed reduced locomotor activity during CPP conditioning compared to male mice. The observed effects illustrate the role DRD4 gene expression has on extinction and reinstatement, but not acquisition, of cocaine-seeking behavior.