SEROTONERGIC MODULATION OF CAT BLADDER FUNCTION BEFORE AND AFTER SPINAL TRANSECTION

Micturition was evoked in conscious cats by infusing saline into the b ladder at a physiological rate. Drugs were administered intrathecally. Micturition volume threshold was increased by 5-hydroxytryptamine (5- HT, serotonin) and decreased by zatosetron, a 5-HT3 receptor antagonis t, in spinally intact cats. Thus 5-HT3 receptors inhibit micturition. After complete spinal transection, serotonin reduced volume threshold in 3 of 4 cats, indicating an alteration in serotonergic control. Howe ver, 2-methyl-5-HT, a 5-HT3 receptor agonist, increased volume thresho ld. Thus 5-HT3 receptor-mediated inhibition of bladder function remain s after spinal transection. We conclude that some, but not all, seroto nergic modulation of bladder function is altered after spinal transect ion.