title: An endogenous pain control system is altered in subjects with interstitial cystitis.
abstract: OBJECTIVE
  Multiple studies have demonstrated that in healthy subjects, painful stimuli applied to one part of the body inhibit pain sensation in other parts of the body, a phenomenon referred to as conditioned pain modulation. Conditioned pain modulation is related to the presence of endogenous pain control systems. Studies have demonstrated deficits in conditioned pain modulation associated inhibition in many but not all chronic pain disorders. In this study we determine whether conditioned pain modulation is altered in subjects with interstitial cystitis/bladder pain syndrome.
  
  
  METHODS
  Female subjects with and without the diagnosis of interstitial cystitis/bladder pain syndrome were studied psychophysically using quantitative cutaneous thermal, forearm ischemia and ice water immersion tests. Conditioned pain modulation was assessed by quantifying the effects of immersion of the hand in ice water (conditioning stimulus) on threshold and tolerance of cutaneous heat pain (test stimulus) applied to the contralateral lower extremity.
  
  
  RESULTS
  The conditioned pain modulation responses of the subjects with interstitial cystitis/bladder pain syndrome were statistically different from those of healthy control subjects for cutaneous thermal threshold and tolerance measures. Healthy control subjects demonstrated statistically significant increases in thermal pain tolerance whereas subjects with the diagnosis of interstitial cystitis/bladder pain syndrome demonstrated statistically significant reductions in thermal pain tolerance.
  
  
  CONCLUSIONS
  An endogenous pain inhibitory system normally observed with conditioned pain modulation was altered in subjects with interstitial cystitis/bladder pain syndrome. This finding identifies interstitial cystitis/bladder pain syndrome as similar to several other chronic pain disorders such as fibromyalgia and irritable bowel syndrome, and suggests that a deficit in endogenous pain inhibitory systems may contribute to such chronic pain disorders.
authors: Department of Anesthesiology, University of Alabama at Birmingham, Birmingham, Alabama. Electronic address: tjness@uab.edu.
authors: Timothy J
authors: TJ
authors: Ness
authors: Department of Urology, University of Alabama at Birmingham, Birmingham, Alabama.
authors: L Keith
authors: LK
authors: Lloyd
authors: University of Florida College of Dentistry and Gainesville Veterans Affairs Medical Center, Gainesville, Florida.
authors: Roger B
authors: RB
authors: Fillingim
mesh_terms: D000328:Adult; D018856:Cystitis, Interstitial / Q000503:physiopathology*; D059328:Diffuse Noxious Inhibitory Control / Q000502:physiology*; D005260:Female; D006801:Humans; D008875:Middle Aged; D010147:Pain Measurement; D058748:Pain Perception / Q000502:physiology*; D013697:Thermosensing / Q000502:physiology; D055815:Young Adult
keywords: BPS; CPM; HC; IC; bladder pain syndrome; conditioned pain modulation; diffuse noxious inhibitory control; healthy control; interstitial cystitis; pain; urinary bladder
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