Alteration of the mu opioid receptor: Ca2+ channel signaling pathway in a subset of rat sensory neurons following chronic femoral artery occlusion

Bassil Hassan, Joyce S. Kim, Mohamed Farrag, Marc P Kaufman, Victor Ruiz-Velasco

Research output: Contribution to journalArticle

9 Scopus citations

Abstract

The exercise pressor reflex, a crucial component of the cardiovascular response under physiological and pathophysiological states, is activated via metabolic and mechanical mediators that originate from contracting muscles and stimulate group III and IV afferents. We reported previously that stimulation of mu opioid receptors (MOR), expressed in both afferents, led to a significant attenuation of the reflex in rats whose femoral arteries had been occluded for 72 h. The present study examined the effect of arterial occlusion on the signaling components involved in the opioid-mediated modulation of Ca2+ channels in rat dorsal root ganglion neurons innervating the triceps surae muscles. We focused on neurons that were transfected with cDNA coding for enhanced green fluorescent protein whose expression is driven by the voltage-gated Na+ channel 1.8 (NaV1.8) promoter region, a channel expressed primarily in nociceptive neurons. With the use of a small interference RNA approach, our results show that the pertussis toxin-sensitive Gai3 subunit couples MOR with Ca2+ channels. We observed a significant leftward shift of the MOR agonist [D-Ala2-N-Me-Phe4-Glycol5]-enkephalin concentration-response relationship in neurons isolated from rats with occluded arteries compared with those that were perfused freely. Femoral occlusion did not affect Ca2+ channel density or the fraction of the main Ca2+ channel subtype. Furthermore, Western blotting analysis indicated that the leftward shift did not result from either increased Gai3 or MOR expression. Finally, all neurons from both groups exhibited an inward current following exposure of the transient potential receptor vanilloid 1 (TRPV1) agonist, 8-methyl-N-vanillyl-6-nonenamide. These findings suggest that sensory neurons mediating the exercise pressor reflex express NaV1.8 and TRPV1 channels, and femoral occlusion alters the MOR pharmacological profile.

Original languageEnglish (US)
Pages (from-to)3104-3115
Number of pages12
JournalJournal of Neurophysiology
Volume112
Issue number12
DOIs
StatePublished - Dec 15 2014
Externally publishedYes

    Fingerprint

Keywords

  • Exercise pressor reflex
  • Na1.8 promoter region
  • Whole-cell patch clamp

ASJC Scopus subject areas

  • Neuroscience(all)
  • Physiology

Cite this