SEROTONERGIC NEUROTOXIC LESIONS FACILITATE MALE SEXUAL REFLEXES

The effects of the neurotoxin 5,7 dihydroxytryptamine (5,7 DHT) on the urethrogenital reflex was examined in anesthetized male rats. Both IC V and intrathecal administration of 5,7 DHT produced a marked depletio n (92%) of spinal 5-hydroxytryptamine (5-HT) and 5-hydroxyindole aceti c acid (5-HT IAA) levels. ICV but not intrathecal administration of 5, 7 DHT also caused a moderate reduction in 5-HT and 5-HT IAA levels in the medulla and hypothalamus (40-48%). No reduction in adrenergic leve ls were observed. In spinally intact, vehicle-treated rats the urethro genital reflex could not be evoked. However, the urethrogenital reflex could be evoked in rats pretreated with either ICV or intrathecal 5,7 DHT prior to section of the spinal cord. These data support the hypot hesis that 5-HT mediates the descending inhibition of male sexual refl exes.