Frontiers in Pain Research (Apr 2023)

Characterization of pain-, anxiety-, and cognition-related behaviors in the complete Freund's adjuvant model of chronic inflammatory pain in Wistar–Kyoto rats

  • Mehnaz I. Ferdousi,
  • Mehnaz I. Ferdousi,
  • Mehnaz I. Ferdousi,
  • Patricia Calcagno,
  • Patricia Calcagno,
  • Patricia Calcagno,
  • Patricia Calcagno,
  • Connie Sanchez,
  • Karen L. Smith,
  • John P. Kelly,
  • John P. Kelly,
  • John P. Kelly,
  • Michelle Roche,
  • Michelle Roche,
  • Michelle Roche,
  • David P. Finn,
  • David P. Finn,
  • David P. Finn

DOI
https://doi.org/10.3389/fpain.2023.1131069
Journal volume & issue
Vol. 4

Abstract

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IntroductionChronic pain is often associated with comorbid anxiety and cognitive dysfunction, negatively affecting therapeutic outcomes. The influence of genetic background on such interactions is poorly understood. The stress-hyperresponsive Wistar–Kyoto (WKY) rat strain, which models aspects of anxiety and depression, displays enhanced sensitivity to noxious stimuli and impaired cognitive function, compared with Sprague–Dawley (SD) counterparts. However, pain- and anxiety-related behaviors and cognitive impairment following induction of a persistent inflammatory state have not been investigated simultaneously in the WKY rats. Here we compared the effects of complete Freund's adjuvant (CFA)-induced persistent inflammation on pain-, negative affect- and cognition-related behaviors in WKY vs. SD rats.MethodsMale WKY and SD rats received intra-plantar injection of CFA or needle insertion (control) and, over the subsequent 4 weeks, underwent behavioral tests to assess mechanical and heat hypersensitivity, the aversive component of pain, and anxiety- and cognition-related behaviors.ResultsThe CFA-injected WKY rats exhibited greater mechanical but similar heat hypersensitivity compared to SD counterparts. Neither strain displayed CFA-induced pain avoidance or anxiety-related behavior. No CFA-induced impairment was observed in social interaction or spatial memory in WKY or SD rats in the three-chamber sociability and T-maze tests, respectively, although strain differences were apparent. Reduced novel object exploration time was observed in CFA-injected SD, but not WKY, rats. However, CFA injection did not affect object recognition memory in either strain.ConclusionsThese data indicate exacerbated baseline and CFA-induced mechanical hypersensitivity, and impairments in novel object exploration, and social and spatial memory in WKY vs. SD rats.

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