Abstract: PD01-03
Sources of Funding: AUA Urology Care Foundation Research Scholar Award. R37 DK54824. NIH RO1 DK57284

Introduction

There is evidence (in patients and preclinical models) that stress can enhance painful sensations in patients with functional pain syndromes such as interstitial cystitis/bladder pain syndrome (IC/BPS). Though the underlying mechanisms have yet to be fully explored, findings reveal increased autonomic (sympathetic) dysregulation as well as a role for central augmentation. In this regard, activation of spinal cord (SC) glial cells can increase excitability of neurons leading to the initiation and maintenance of bladder hyperalgesia and impaired bladder storage function (urgency, frequency). Our goal was to examine whether chronic stress (using the water avoidance stress or WAS model) can alter neural-glial distribution and chemistry, which may play a role in micturition and pain behavior.

Methods

Adult female Wistar-Kyoto rats were exposed to WAS by placement on a pedestal in a water-filled container (1hr/day x10 consecutive days) versus handled controls. Previous published findings have revealed WAS rats exhibit long-lasting urinary frequency and hyperalgesia. SC (L6) were harvested from anesthetized animals, and either cryosectioned (for immunocytochemistry) or homogenized (for RT-PCR). The following were investigated: calcitonin gene-related peptide (CGRP; sensory fibers), microglia (IBA-1), Toll-like receptor (TLR-4), purinergic receptor subtypes (P2X4, P2X7). Separate groups of both WAS and control animals were treated 2 days prior then every other day with the adrenergic antagonist phenoxybenzamine (PB; 2 mg/kg i.p.) or saline, respectively.

Results

WAS increased neural CGRP (40%) and IBA-1 (2 fold) expression in the L6 SC dorsal horn and central canal (regions receiving input from nociceptive fibers). We find PB reduced CGRP expression (92% decrease) as well as IBA-1 in WAS SC. Further, both TLR-4 as well as P2X4 and P2X7 purinergic receptor are increased (50%) in WAS, suggesting microglia activation with chronic stress.

Conclusions

Taken together, our findings suggest increased communication between the sympathetic nervous system and bladder sensory neurons that may play an important role in chronic pain conditions. This includes abnormal neural sprouting and altered morphology and chemistry of SC glial cells, which are likely to play an important role in modifying neural activity resulting in changes in bladder function and sensory mechanisms.

Funding

AUA Urology Care Foundation Research Scholar Award. R37 DK54824. NIH RO1 DK57284