Constitutive activity of the dopamine (D5) receptor, highly expressed in CA1 hippocampal neurons, selectively reduces CaV3.2 and CaV3.3 currents

Abstract

Background and Purpose: CaV3.1-3 currents differentially contribute to neuronal firing patterns. CaV3 are regulated by G protein-coupled receptors (GPCRs) activity, but information about CaV3 as targets of the constitutive activity of GPCRs is scarce. We investigate the impact of D5 recpetor constitutive activity, a GPCR with high levels of basal activity, on CaV3 functionality. D5 recpetor and CaV3 are expressed in the hippocampus and have been independently linked to pathophysiological states associated with epilepsy. Experimental Approach: Our study models were HEK293T cells heterologously expressing D1 or D5 receptor and CaV3.1-3, and mouse brain slices containing the hippocampus. We used chlorpromazine (D1/D5 inverse agonist) and a D5 receptor mutant lacking constitutive activity as experimental tools. We measured CaV3 currents and excitability parameters using the patch-clamp technique. We completed our study with computational modelling and imaging technique. Key Results: We found a higher sensitivity to TTA-P2 (CaV3 blocker) in CA1 pyramidal neurons obtained from chlorpromazine-treated animals compared with vehicle-treated animals. We found that CaV3.2 and CaV3.3—but not CaV3.1—are targets of D5 receptor constitutive activity in HEK293T cells. Finally, we found an increased firing rate in CA1 pyramidal neurons from chlorpromazine-treated animals in comparison with vehicle-treated animals. Similar changes in firing rate were observed on a neuronal model with controlled CaV3 currents levels. Conclusions and Implications: Native hippocampal CaV3 and recombinant CaV3.2-3 are sensitive to D5 receptor constitutive activity. Manipulation of D5 receptor constitutive activity could be a valuable strategy to control neuronal excitability, especially in exacerbated conditions such as epilepsy.