Login to Access Video or Poster Abstract: MP29-09
Sources of Funding: DOD W81XWH-12-1-0565; NIH DK088836

Introduction

We investigated whether spinal cord microglia are involved in colon-to-bladder neural crosstalk in a rat model of colitis.

Methods

Adult female SD rats were divided into A) control, B) colitis, and C) colitis + minocycline groups. Experimental colitis was induced by instilling 50% trinitrobenzene sulfonic acid into the distal colon in groups B and C; vehicle was administered in group A. Minocycline (200 mg/day), a microglial inhibitor, was continuously infused into the intrathecal space in group C; groups A and B were given the vehicle. On day 7: _x000D_ (1) an awake cystometrogram (CMG) was performed; _x000D_ (2) nociceptive licking and freezing behavior induced by intravesical instillation of resiniferatoxin was observed;_x000D_ (3) the distal colon was stained with hematoxylin-eosin (HE);_x000D_ (4) immunofluorescence staining for CD 11b, a microglial marker, was performed on the L6 spinal cord;_x000D_ (5) reverse transcription polymerase chain reaction for mRNA was performed on the L6 spinal cord;_x000D_ (6) the bladder was stained with toluidine blue._x000D_

Results

(1) CMG in group B showed significantly (p < 0.01) shorter intercontraction intervals (ICI) than in group A. Group C showed significantly (p < 0.01) longer ICI than group B._x000D_ (2) There were no significant differences in licking events among the 3 groups. However, the number of freezing events was significantly (p < 0.01) greater in group B than in group A. Group C showed significantly (p < 0.05) fewer freezing events than group B._x000D_ (3) HE staining showed substantial inflammation in the distal colon in groups B and C compared with that in group A. _x000D_ (4) The number of CD 11b-positive cells significantly differed among groups in the following order: group B > group C > group A._x000D_ (5) The mRNA expressions of interleukin-1β, chemokine ligand 3, and brain-derived neurotrophic factor in the L6 spinal cord were significantly (p<0.05) increased in group B compared with those in group A. However, group C showed significantly (p<0.05) less mRNA expression of these molecules than group B._x000D_ (6) Toluidine blue staining in group B showed significantly (p<0.01) more total and degranulated mast cells in the bladder than group A. Group C showed significantly (p<0.05) fewer total and degranulated mast cells in the bladder than group B. _x000D_

Conclusions

Spinal microglia probably play an important role in colitis-induced bladder overactivity and enhanced bladder pain sensitivity in colitic rats.

Funding

DOD W81XWH-12-1-0565; NIH DK088836