*5.2. Voltage-Gated Calcium Channels*

Several lines of evidence have shown that DRG and spinal cord neurons express CaV1.2 [166], while L-type CaV channels are broadly expressed in skeletal and cardiac muscle, neurons, auditory hair cells, pancreatic cells, and the retina [167]. Electrophysiological examination of the DRG showed that L-type CaV channels are present largely in small and large neurons, although these channels are regulated during chronic pain [168]. One study using RT-PCR showed that L-type CaV channels are downregulated in DRG upon chronic constriction injury (CCI) and sciatic nerve axotomy in rats [169]. suggesting that decreases in CaV1.2 and CaV1.3 in DRG could contribute to the hyperexcitability of neuropathic pain by modulating Ca2+-dependent inactivation or facilitation as negative feedback [170]. Inversely, CaV1.2 is upregulated in the spinal cord in a spinal nerve ligation (SNL) model. One study reported that Cav1.2 functions as a key factor for the differentiation of tooth pulp stem cells [171]. In addition, several lines of evidence indicate that CaV1.2 may have a central role in odontoblast behavior at both the physiological and pathological levels [31,172–174].
