Contribution of D1R-expressing neurons of the dorsal dentate gyrus and Ca v 1.2 channels in extinction of cocaine conditioned place preference.

Cocaine-associated contextual cues can trigger relapse behavior by recruiting the hippocampus. Extinction of cocaine-associated contextual memories can reduce cocaine-seeking behavior, however the molecular mechanisms within the hippocampus that underlie contextual extinction behavior and subsequent reinstatement remain poorly understood. Here, we extend our previous findings for a role of Ca _v 1.2 L-type Ca ²⁺ channels in dopamine 1 receptor (D1R)-expressing cells in extinction of cocaine conditioned place preference (CPP) in adult male mice. We report that attenuated cocaine CPP extinction in mice lacking Ca _v 1.2 channels in D1R-expressing cells (D1 ^cre , Ca _v 1.2 ^fl/fl ) can be rescued through chemogenetic activation of D1R-expressing cells within the dorsal dentate gyrus (dDG), but not the dorsal CA1 (dCA1). This is supported by the finding that Ca _v 1.2 channels are required in excitatory cells of the dDG, but not in the dCA1, for cocaine CPP extinction. Examination of the role of S1928 phosphorylation of Ca _v 1.2, a protein kinase A (PKA) site using S1928A Ca _v 1.2 phosphomutant mice revealed no extinction deficit, likely due to homeostatic scaling up of extinction-dependent S845 GluA1 phosphorylation in the dDG. However, phosphomutant mice failed to show cocaine-primed reinstatement which can be reversed by chemogenetic manipulation of excitatory cells in the dDG during extinction training. These findings outline an essential role for the interaction between D1R, Ca _v 1.2, and GluA1 signaling in the dDG for extinction of cocaine-associated contextual memories.