Chronic stress exacerbates neuropathic pain via the integration of stress-affect-related information with nociceptive information in the central nucleus of the amygdala

Pain. 2017 Apr;158(4):717-739. doi: 10.1097/j.pain.0000000000000827.

Abstract

Exacerbation of pain by chronic stress and comorbidity of pain with stress-related psychiatric disorders, including anxiety and depression, represent significant clinical challenges. However, the underlying mechanisms still remain unclear. Here, we investigated whether chronic forced swim stress (CFSS)-induced exacerbation of neuropathic pain is mediated by the integration of stress-affect-related information with nociceptive information in the central nucleus of the amygdala (CeA). We first demonstrated that CFSS indeed produces both depressive-like behaviors and exacerbation of spared nerve injury (SNI)-induced mechanical allodynia in rats. Moreover, we revealed that CFSS induces both sensitization of basolateral amygdala (BLA) neurons and augmentation of long-term potentiation (LTP) at the BLA-CeA synapse and meanwhile, exaggerates both SNI-induced sensitization of CeA neurons and LTP at the parabrachial (PB)-CeA synapse. In addition, we discovered that CFSS elevates SNI-induced functional up-regulation of GluN2B-containing NMDA (GluN2B-NMDA) receptors in the CeA, which is proved to be necessary for CFSS-induced augmentation of LTP at the PB-CeA synapse and exacerbation of pain hypersensitivity in SNI rats. Suppression of CFSS-elicited depressive-like behaviors by antidepressants imipramine or ifenprodil inhibits the CFSS-induced exacerbation of neuropathic pain. Collectively, our findings suggest that CFSS potentiates synaptic efficiency of the BLA-CeA pathway, leading to the activation of GluN2B-NMDA receptors and sensitization of CeA neurons, which subsequently facilitate pain-related synaptic plasticity of the PB-CeA pathway, thereby exacerbating SNI-induced neuropathic pain. We conclude that chronic stress exacerbates neuropathic pain via the integration of stress-affect-related information with nociceptive information in the CeA.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Action Potentials / physiology
  • Animals
  • Body Weight / physiology
  • Central Amygdaloid Nucleus / cytology
  • Central Amygdaloid Nucleus / drug effects
  • Central Amygdaloid Nucleus / physiology*
  • Disease Models, Animal
  • Food Preferences / psychology
  • Hyperalgesia / physiopathology
  • Locomotion / physiology
  • Long-Term Potentiation / drug effects
  • Long-Term Potentiation / physiology
  • Male
  • Maze Learning / physiology
  • Neuralgia / complications*
  • Neurons / physiology
  • Pain Threshold / physiology
  • Rats
  • Rats, Sprague-Dawley
  • Stress, Psychological / complications*
  • Sucrose
  • Swimming / psychology
  • Synaptosomes / metabolism

Substances

  • Sucrose