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Objectives: To examine the effect of intrathecal (i.t.) serotonin (5‐hydroxytryptamine) 5‐HT7 agonist administration on voiding function in the urethane‐anesthetised rat, and the change in 5‐HT7 receptor (5‐HT7R) expression in the lumbosacral cord Onuf's nucleus after spinal cord injury (SCI). Materials and methods: In all, 32 female Sprague–Dawley (SD) rats were equally divided into a spinally intact (SI) group and SCI group (n = 16 each). At 8 weeks after transection, half of the rats underwent continuous cystometry under urethane anaesthesia, and the 5‐HT7R‐selective agonist LP44 was given (i.t.). The remaining rats were used for pseudorabies (PRV) retrograde tracing, immunofluorescence, and Western Blot. Results: LP44 administered i.t. had no effect in the SI rats. In SCI rats, LP44 (1–30 μg/kg) induced significant dose‐dependent increases in micturition volume, voiding efficiency, number of high‐frequency oscillations per micturition; and decreases in residual volume, bladder capacity, peak bladder pressure, threshold pressure and non‐voiding contractions. The 5‐HT7R antagonist, SB‐269970 (10 μg/kg), partially reversed LP44‐induced changes. Using PRV retrograde tracing and immunofluorescence, 5‐HT7Rs were found in the L6–S1 spinal cord Onuf's nucleus in both SI and SCI rats, but the expression was significantly greater in the SCI rats. Western blot showed significantly more 5‐HT7Rs in the ventral L6–S1 spinal cord in SCI rats. Conclusion: A 5‐HT7R agonist, given i.t., improved voiding efficiency in urethane‐anesthetised SCI rats, and the 5‐HT7R was significantly up‐regulated in the lumbosacral cord Onuf's nucleus. If valid for humans, these findings suggest that the 5‐HT7R could be a target for therapeutic interventions. [ABSTRACT FROM AUTHOR]

Objectives: To investigate whether the voiding dysfunction caused by spinal cord injury (SCI) in rats can be improved by i.v. administration of the serotonin (5‐HT)2A/2C receptor agonist 2,5‐dimethoxy‐4‐iodophenyl‐2‐aminopropanehydrochloride (DOI), and to discuss whether the mechanism can be ascribed to 5‐HT2A and 5‐HT 2C receptor upregulation in lumbosacral cord motoneurons. Materials and Methods: Female Sprague–Dawley rats were divided into two groups (SCI 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. Changes in 5‐HT2A and ‐2C receptors in the lumbosacral cord were also investigated using immunohistochemical staining and Western blot analysis. Results: Compared with NC rats, the SCI rats had higher bladder capacity and post‐void residual urine volume, and lower voiding efficiency. After SCI, DOI improved voiding efficiency, probably via external urethral sphincter (EUS) activity. Immunohistochemical staining and Western blot analysis showed that 5‐HT2A and ‐2C receptors were upregulated in lumbosacral cord motoneurons. Conclusion: In rats with SCI, DOI can improve voiding efficiency; this may be attributable to 5‐HT2A and ‐2C receptor upregulation in lumbosacral cord motoneurons controlling EUS activity. [ABSTRACT FROM AUTHOR]