Effects of p-chloroamphetamine and 5,7-dihydroxytryptamine on the sexual behavior of gonadectomized male and female rats.

Treatment with the 5-HT neurotoxins p-chloroamphetamine (PCA, 2 X 10 mg/kg) or 5,7-dihydroxytryptamine (5,7-DHT, 2 X 6 microgram intracerebrally) stimulated the display of all aspects of sexual behavior, including ejaculations, by castrated male rats in the absence of testosterone (T) treatment and increased the behavioral sensitivity to a low level of T stimulation. The reduction of the (3H) 5-HT uptake after PCA treatment was more pronounced in the cortex than in the hypothalamus. 5,7-DHT treatment reduced the (3H) 5-HT uptake in the septum, hippocampus, amygdala, hypothalamus and cortex but the behavioral effects produced by the 5,7-DHT treatment could not be correlated to the biochemical effects in any of these brain areas. Since the behavioral effect of PCA appears to be stronger than that of 5,7-DHT, the 5-HT neurotoxins may exert their effect on sexual behavior in forebrain structures rather than in the hypothalamus. PCA treatment had a very small effect on mounting behavior but 5,7-DHT treatment stimulated the display of mounts and intromission patterns by ovariectomized female rats given no hormone treatment. Neither PCA nor 5,7-DHT had any effect on lordosis behavior tested before and after treatment with estradiol benzoate alone or in combination with progesterone. The observations support the conclusion that 5-HT is involved in the control by T of sexual behavior in male rats, but argue against a role of 5-HT in the neural control of lordosis behavior.