Pharmacological characterization of a rat Nav1.7 loss-of-function model with insensitivity to pain. Issue 6 (June 2020)

• Record Type: Journal Article
• Authors: Chen, Lubin; Effraim, Philip R.; Carrara, Jennifer; Zhao, Peng; Dib-Hajj, Fadia B.; Dib-Hajj, Sulayman D.; Waxman, Stephen G.
• Is Part Of: Pain. Volume 161:Issue 6(2020)
• Publication Date: 2020-06
• Subjects: Nav1.7 -- CIP -- Nav1.7-related CIP -- Endogenous opioid -- Endogenous cannabinoid -- SR141716A -- CB1 -- Itch; Pain -- Periodicals; Douleur -- Périodiques; Anesthésie -- Périodiques; Pain; Electronic journals; Periodicals; Electronic journals; 616.0472
• DOI: 10.1097/j.pain.0000000000001807
• Languages: English
• ISSNs: 0304-3959

Abstract

Abstract : Abstract: Sodium channel Nav 1.7, encoded by the SCN9A gene, is a well-validated target that plays a key role in controlling pain sensation. Loss-of-function mutations of Nav 1.7 can cause a syndrome of profound congenital insensitivity to pain in humans. Better understanding of how the loss of Nav 1.7 leads to loss of pain sensibility would help to decipher the fundamental mechanisms of nociception and inform strategies for development of novel analgesics. Using a recently described rat Nav 1.7 loss-of-function model with deficient nociception but intact olfactory function, we investigated the involvement of endogenous opioid and cannabinoid systems in this rodent model of Nav 1.7-related congenital insensitivity to pain. We found that both the opioid receptor antagonist naloxone and cannabinoid receptor blockers SR141716A (rimonabant) and SR144528 fail to restore acute pain sensitivity in Nav 1.7 loss-of-function rats. We observed, however, that after rimonabant administration, Nav 1.7 loss-of-function but not WT rats displayed abnormal behaviours, such as enhanced scratching, caudal self-biting, and altered facial expressions; the underlying mechanism is still unclear. Dorsal root ganglion neurons from Nav 1.7 loss-of-function rats, although hypoexcitable compared with WT neurons, were still able to generate action potentials in response to noxious heat and capsaicin. Our data indicate that complete loss of dorsal root ganglion neuron excitability is not required for insensitivity to pain and suggest that endogenous opioid and cannabinoid systems are not required for insensitivity to pain in the absence of Nav 1.7 channels in this rat Nav 1.7 loss-of-function model. Abstract : Supplemental Digital Content is Available in the Text.Neither complete loss of dorsal root ganglion neuron excitability nor endogenous opioid and cannabinoid systems are required for insensitivity to pain in the rat Nav 1.7 loss-of-function model.