CACNA1B and peripheral nerve injury: The intrathecal analgesic effects of morphine in vivo [35] and, most relevant to this discussion, abnormal cell-specific splicing of CaV2.2 in heat-sensitive Trpv1 nociceptors following peripheral nerve injury, leads to reduced expression of the e37a splice isoform of CaV2.2 and an accompanying reduction in the analgesic efficacy of morphine [25,34,36].