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

Neuropharmacology. 2013 Dec;75:1-8. doi: 10.1016/j.neuropharm.2013.06.018. Epub 2013 Jun 26.

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.

Keywords: CGRP; DRG; G protein-coupled receptor; GPCR; IB4; IR; IT; N-methyl-d-aspartate; NK1r; NMDA; Neurokinin 1 receptor; SNX-482; SP; Spinal cord; TRPV1; VSCCs; Voltage sensitive calcium channels; c-Fos; calcitonin gene-related peptide; dorsal root ganglia; immunoreactive; intrathecal; isolectin B4; neurokinin 1 receptor; substance P; transient receptor potential protein vanilloid 1; trkA; tropomyosin receptor kinase A; voltage-sensitive calcium channels; ω-Agatoxin IVA.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Calcium Channel Blockers / pharmacology*
  • Dose-Response Relationship, Drug
  • Injections, Spinal
  • Male
  • Movement Disorders / etiology
  • Pain Measurement / drug effects
  • Phosphopyruvate Hydratase / metabolism
  • Protein Transport / drug effects
  • Proto-Oncogene Proteins c-fos / metabolism*
  • Rats
  • Rats, Sprague-Dawley
  • Receptors, Neurokinin-1 / metabolism
  • Spider Venoms / pharmacology
  • Spinal Cord / drug effects*
  • Spinal Cord / metabolism
  • Substance P / metabolism*
  • Touch / drug effects
  • Touch / physiology
  • Vocalization, Animal / drug effects
  • omega-Agatoxin IVA / pharmacology

Substances

  • Calcium Channel Blockers
  • Proto-Oncogene Proteins c-fos
  • Receptors, Neurokinin-1
  • SNX 482
  • Spider Venoms
  • omega-Agatoxin IVA
  • Substance P
  • Phosphopyruvate Hydratase