Chronic psychological stress enhances nociceptive processing in the urinary bladder in high-anxiety rats

This study sought to determine whether acute and/or chronic psychological stress produce changes in urinary bladder nociception. Female Sprague–Dawley (SD; low/moderate anxiety) or Wistar–Kyoto (WK; high-anxiety) rats were exposed to either an acute (1 day) or a chronic (10 days) water avoidance stress paradigm or a sham stress paradigm. Paw withdrawal thresholds to mechanical and thermal stimuli and fecal pellet output, were quantified at baseline and after the final stress or sham stress exposure. Rats were then sedated, and visceromotor responses (VMRs) to urinary bladder distension (UBD) were recorded. While acute stress exposure did not significantly alter bladder nociceptive responses in either strain of rats, WK rats exposed to a chronic stress paradigm exhibited enhanced responses to UBD. These high-anxiety rats also exhibited somatic analgesia following acute, but not chronic, stress. Furthermore, WK rats had greater fecal pellet output than SD rats when stressed. Significant stress-induced changes in nociceptive responses to mechanical stimuli were observed in SD rats. That chronic psychological stress significantly enhanced bladder nociceptive responses only in high-anxiety rats provides further support for a critical role of genetics, stress and anxiety as exacerbating factors in painful urogenital disorders such as interstitial cystitis (IC).