The effect of the 5-HT2A/2C receptor agonist DOI on micturition in rats with chronic spinal cord injury.

We examined the effects of the 5-HT2A/2C receptor agonist DOI on micturition in chronic spinal cord injured rats. Female Sprague-Dawley® rats were used. Spinal cord injury was produced by transection at the T10 level. A cystometric study was performed 8 to 12 weeks after transection. Cystometrograms were done using urethane anesthesia in all rats. The selective 5-HT2A antagonist ketanserin was administered after each DOI dose-response curve. All drugs were administered intravenously. Compared to controls, spinal cord injured rats had higher bladder capacity and post-void residual urine volume, and lower voiding efficiency. In spinal cord injured rats DOI (0.01 to 0.3 mg/kg) induced significant dose dependent increases in micturition volume and decreases in residual volume, resulting in increased voiding efficiency. Cystometrogram measurements showed a dose dependent increase in high frequency oscillation activity, evident as an increased number of small oscillation per voiding. This correlated with the improved voiding efficiency. Ketanserin (0.1 mg/kg) partially or completely reversed the DOI induced changes. High frequency oscillation seems to reflect external urethral sphincter burst activity during voiding. Bladder voiding efficiency and high frequency oscillation activity were decreased in spinal cord injured rats. High frequency oscillation activity can be enhanced by 5-HT2A receptor agonism, improving voiding efficiency. To our knowledge it remains to be studied whether these results may have implications for the future treatment of voiding dysfunction in patients with spinal cord injury.