Evidence for the involvement of central 5‐HT 7 receptors in the micturition reflex in anaesthetized female rats

The effects of the selective 5‐HT 7 receptor antagonists SB‐269970 (3‐300 μ g kg −1 ; n =5–6) and SB‐656104 (30 μ g kg −1 ; n =5) administered centrally (i.c.v.) were investigated on the ‘micturition reflex’ in the urethane anaesthetized female rat. In cystometric recordings, SB‐269970 caused significant increases in volume of 58±15 and 138±33% and pressure of 140±46 and 149±60% thresholds at 10 and 30 μ g kg −1 . These changes were associated with significant decreases in distension‐induced bladder contraction of 62±14 and 60±11%, respectively. However, there was no change in residual volume. At the higher doses, SB‐269970 blocked the micturition reflex. SB‐656104 had similar effects to SB‐269970 but in addition significantly increased the residual volume. SB‐269970 (10 μ g kg −1 ; n =5) given i.v. had no effect on the micturition reflex. SB‐269970 (30 μ g kg −1 ; n =4) given intrathecally (i.t.) had no effect on micturition reflex, although the selective 5‐HT 1A receptor antagonist WAY‐100635 given i.t. after SB‐269970 caused a significant increase in the volume threshold. Using an isovolumetric method in which urethral changes were measured, SB‐269970 (30 μ g kg −1 ; n =4; i.c.v.) failed to have any effect on these urethral‐evoked changes although they significantly reduced the amplitude of the bladder contraction. These data demonstrate that 5‐HT 7 receptors located supraspinally in the rat are involved in the control of micturition.British Journal of Pharmacology (2003) 140 , 53–60. doi: 10.1038/sj.bjp.0705399