Intrathecal P/Q- and R-type calcium channel blockade of spinal substance P release and c-Fos expression

Abstract

Intrathecal (IT) studies have shown that several voltage sensitive calcium channels (VSCCs), such as the L-, N- and T-type may play roles in nociception and that of these only the N-type regulates primary afferent substance P (SP) release. However, the actions of other VSCCs at the spinal level are not well known. We investigated the roles of spinal P/Q- and R-type VSCCs, by IT administration of R-type (SNX-482) and P/Q-type (ω-agatoxin IVA) VSCC blockers on intraplantar formalin-evoked flinching, SP release from primary afferents and c-Fos expression in spinal dorsal horn. Intraplantar injection of formalin (2.5%, 50 µL) produced an intense, characteristic biphasic paw flinching response. In rats with IT catheters, IT SNX-482 (0.5 µg) reduced formalin-evoked paw flinching in both phase 1 and 2 compared with vehicle. Intraplantar formalin caused robust neurokinin 1 receptor (NK1r) internalization (indicating SP release) and c-Fos expression in the ipsilateral dorsal horn, which were blocked by IT SNX-482. IT ω-agatoxin IVA (0.03, 0.125 and 0.5 µg) did not reduce formalin-evoked paw flinching or c-Fos expression at any doses, with higher doses resulting in motor dysfunction. Thus, we demonstrated that blockade of spinal R-type, but not P/Q type VSCCs attenuated formalin-induced pain behavior, NK1r internalization and c-Fos expression in the superficial dorsal horn. This study supports a role for Cav2.3 in presynaptic neurotransmitter release from peptidergic nociceptive afferents and pain behaviors.

Sustained relief of ongoing experimental neuropathic pain by a CRMP2 peptide aptamer with low abuse potential

“…Additionally, central blockade of CaV2.2 is effective in treatment of cases of chronic pain that are intractable to other interventions [11]. Other subtypes of calcium channels, such as CaV2.3 (R-type) [54; 72; 81] or CaV3 (T-type)[35; 51; 58], have also been indicated to play important roles in chronic pain. The CaV2.3-selective blocker, SNX-482, has been reported to block the C- and Aδ- fiber neurotransmission in animal models of chronic neuropathic pain [54] and reduce formalin induced paw-flinching and FOS-expression in the ipsilateral spinal cord [81].…”

Substance P stimulates proliferation of spinal neural stem cells in spinal cord injury via the mitogen-activated protein kinase signaling pathway

“…In present study, we did not analyze the pain behavior after SP injection, and there was no behavioral change or extraordinary reaction after injection compared with the control group. However, many studies suggested that SP of the spinal cord is linked closely to nociceptive change [40][41][42]; so, a welldesigned study is needed to clarify the pain behavior after SP injection.…”

Voltage-Gated R-Type Calcium Channel Inhibition via Humanμ-,δ-, andκ-opioid Receptors Is Voltage-Independently Mediated by GβγProtein Subunits

“…Genetic research approaches confirmed this, with Ca v 2.3 knockout mice exhibiting reduced pain perception (Saegusa et al, 2000;Yang and Stephens, 2009). In pharmacological studies, intrathecal delivery of the Ca v 2.3 channel blocker SNX-482, a toxin from the tarantula Hysterocrates gigas, produces analgesia in animal models of neuropathic pain Terashima et al, 2013). Despite the clear functional importance of Ca v 2.3 channels in pain pathways, the mechanisms by which they are modulated by GPCRs have not yet been adequately examined (Rittenhouse, 2014).…”