Cold environmental stress induces detrusor overactivity via resiniferatoxin-sensitive nerves in conscious rats

Aims: We determined if cold environmental stress induced detrusor overactivity in conscious rats. We then examined the role of resiniferatoxin (RTX)-sensitive nerves in this response. Methods: Three days prior to cystometric investigation, the urinary bladders of 12 female rats were cannulated. Six of the rats were treated with RTX 24 hr prior to cystometric investigation. The rats were exposed to three ambient temperature conditions: room temperature (RT, 27 degrees C) for 20 min, low temperature (LT, 4 degrees C) for 40 min, and RT again for 20 min. During each exposure, cystometric patterns of the rats were recorded. Additionally, neuronal structures of urinary bladders were visualized by immunohistochemistry. Results: When the conscious rats were suddenly transferred from RT to LT, the cooled rats exhibited micturition patterns of detrusor overactivity. After 20 min at LT, the response slowly improved. After returning to RT, the overactive detrusor response disappeared, reverting to patterns similar to those before transfer to LT. When the RTX-treated rats were exposed with cold stress, they also exhibited detrusor overactivity. However, it was significantly mitigated compared to the non-RTX-treated normal rats. The normal rats had distinct neuronal structures labeled with S100 and calcitonin gene-related peptide antibodies in the urinary bladders, but the RTX-treated rats had few. Conclusion: Detrusor overactivity of the conscious rats was induced by cold environmental stress. A portion of the cold-stress detrusor overactivity might be mediated by RTX-sensitive neurological pathway. The cold-stress model would be useful to investigate lower urinary tract functions.