Effects of WAY100635, a selective 5-HT1A-receptor antagonist on the micturition-reflex pathway in the rat

5-Hydroxytryptamine (5-HT) receptors in the central nervous system have bee n implicated in the control of micturition. The present study was undertake n to evaluate the effects of a selective 5-HT1A-receptor antagonist {N-[2-[ 4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-N-(2-pyridinyl) cyclohexanecarboxa mide trihydrochloride (WAY100635)} on the micturition-reflex pathway in ure thane-anesthetized female Wistar rats. Rhythmic isovolumetric bladder contr actions evoked by bladder distension were abolished by 0.3- to 3-mg/kg iv o r 30- to 100-mug intrathecal (it) administration of WAY100635 in a dose-dep endent manner for periods of 3-15 min. Intrathecal injection of WAY100635 w as effective only if injected at the L6-S1 spinal cord level, but not at th e thoracic or cervical cord levels. WAY100635 (30-100 mug it) significantly reduced the amplitude of bladder contractions evoked by electrical stimula tion of the pontine micturition center. However, the field potentials in th e rostral pons evoked by electrical stimulation of pelvic nerve were not af fected by intrathecal or intravenous injection of WAY100635. These results suggest that 5-HT1A receptors at the L6-S1 level of the spinal cord have an important role in the tonic control of the descending limb of the micturit ion-reflex pathway in the rat.