To examine the effect of intrathecal serotonin (5-HT)2A/2C receptor agonist administration on voiding function in urethane-anesthetized rat, and the change of (5-HT)2A and 2C receptor expression in lumbosacral cord Onuf’s nucleus with Diabetes Mellitus (DM).

Female Sprague–Dawley rats were divided into two groups (DM group vs normal control [NC] group). Under urethane anaesthesia, cystometry was performed to examine the variation in urodynamic variables before and after successive intrathecal (i.t.) administration of various doses of DOI into the lumbosacral cord. Half of the remaining rats were used for pseudorabies (PRV) retrograde tracing, immunofluorescence (IF) and Western Blot.

Compared with NC rats, the DM rats had higher bladder capacity and post-void residual urine volume, and lower voiding efficiency. After DM, DOI improved voiding efficiency, probably via external urethral sphincter (EUS) activity(Fig 1). By PRV retrograde tracing and IF, 5-HT2A and 5-HT2C receptors were demonstrated in L6-S1 spinal cord Onuf’s nucleus in both NC and DM rats, but the expression was significantly stronger in DM rats (Fig.2). Western blot showed a significant increase of 5-HT2A and 5-HT2C receptors in ventral L6-S1 spinal cord in DM rats

These results indicate that: (1). DOI improved voiding efficiency, which probably increase external urethral sphincter (EUS) activity. (2)  5-HT2A and 5-HT2C receptors were demonstrated in L6-S1 spinal cord Onuf’s nucleus in both NC and DM rats, but the expression was significantly stronger in DM rats.Thus, it is assumed that intrathecal injection of DOI can improve voiding efficiency and this may be attributed to 5-HT2A and -2C receptor upregulation in Onuf’s nucleus controlling EUS activity.

In rats with DM, DOI can improve voiding efficiency; this may be attributed to 5-HT2A and -2C receptor upregulation in Onuf’s nucleus controlling EUS activity.