Differential regulation of Cav3.2 and Cav2.2 calcium channels by CB1 receptors and cannabidiol

Abstract

Background and PurposeCannabinoids are a promising therapeutic avenue for chronic pain. However, clinical trials often fail to report analgesic efficacy of cannabinoids. Inhibition of voltage gate calcium (Cav) channels is one mechanism through which cannabinoids may produce analgesia. We hypothesized that cannabinoids and cannabinoid receptor agonists target different types of Cav channels through distinct mechanisms.Experimental ApproachElectrophysiological recordings from tsA‐201 cells expressing either Cav3.2 or Cav2.2 were used to assess inhibition by HU‐210 or cannabidiol (CBD) in the absence and presence of the CB1 receptor. Homology modelling assessed potential interaction sites for CBD in both Cav2.2 and Cav3.2. Analgesic effects of CBD were assessed in mouse models of inflammatory and neuropathic pain.Key ResultsHU‐210 (1 μM) inhibited Cav2.2 function in the presence of CB1 receptor but had no effect on Cav3.2 regardless of co‐expression of CB1 receptor. By contrast, CBD (3 μM) produced no inhibition of Cav2.2 and instead inhibited Cav3.2 independently of CB1 receptors. Homology modelling supported these findings, indicating that CBD binds to and occludes the pore of Cav3.2, but not Cav2.2. Intrathecal CBD alleviated thermal and mechanical hypersensitivity in both male and female mice, and this effect was absent in Cav3.2 null mice.Conclusion and ImplicationsOur findings reveal differential modulation of Cav2.2 and Cav3.2 channels by CB1 receptors and CBD. This advances our understanding of how different cannabinoids produce analgesia through action at different voltage‐gated calcium channels and could influence the development of novel cannabinoid‐based therapeutics for treatment of chronic pain.