Up-regulation of Cavβ3 Subunit in Primary Sensory Neurons Increases Voltage-activated Ca2+ Channel Activity and Nociceptive Input in Neuropathic Pain

High voltage-activated calcium channels (HVACCs) are essential for synaptic and nociceptive transmission. Although blocking HVACCs can effectively reduce pain, this treatment strategy is associated with intolerable adverse effects. Neuronal HVACCs are typically composed of alpha(1), beta (Cav beta), and alpha(2)delta subunits. The Cav beta subunit plays a crucial role in the membrane expression and gating properties of the pore-forming alpha(1) subunit. However, little is known about how nerve injury affects the expression and function of Cav beta subunits in primary sensory neurons. In this study, we found that Cav beta(3) and Cav beta(4) are the most prominent subtypes expressed in the rat dorsal root ganglion (DRG) and dorsal spinal cord. Spinal nerve ligation (SNL) in rats significantly increased mRNA and protein levels of the Cav beta(3), but not Cav beta(4), subunit in the DRG. SNL also significantly increased HVACC currents in small DRG neurons and monosynaptic excitatory postsynaptic currents of spinal dorsal horn neurons evoked from the dorsal root. Intrathecal injection of Cav beta(3)-specific siRNA significantly reduced HVACC currents in small DRG neurons and the amplitude of monosynaptic excitatory postsynaptic currents of dorsal hornneurons in SNL rats. Furthermore, intrathecal treatment with Cav beta(3)-specific siRNA normalized mechanical hyperalgesia and tactile allodynia caused by SNL but had no significant effect on the normal nociceptive threshold. Our findings provide novel evidence that increased expression of the Cav beta(3) subunit augments HVACC activity in primary sensory neurons and nociceptive input to dorsal horn neurons in neuropathic pain. Targeting the Cav beta(3) subunit at the spinal level represents an effective strategy for treating neuropathic pain.