Mounting and Lordosis Behavior in Androgen Primed Ovariectomized Rats

Effect of Dorsal Deafferentation of the Preoptic Area and Hypothalamus

Abstract

Daily injections of 500μg testosterone propionate (TP) for 21days induced mounting behavior in all of 10 castrated male rats and the mean mount frequency (MF) for 30min was 32.4±6.6 (mean±S. E.). The same treatment with TP induced mounting behavior in 6 out of 8 ovariectomized rats (female control), but the mean MF was 2.8±0.7. Eight out of 12 ovariectomized rats which received a horizontal half-circle cut anterior to the anterior commissure (anterior roof deafferentation, ARD) with an L-shaped Halasz knife displayed mounting behavior more frequently and their MF was 14.5±5.1. The latent period between the introduction of a receptive female and the occurrence of the first mounting (mount latency, ML) in ARD rats was significantly shorter than that of the female controls. A half circle cut located posterior to the anterior commissure (posterior roof deafferentation, PRD) and sham deafferentation (SD) in the female rats had no effect on MF and ML.
On the day following the last test for male behavior, all female rats were injected with 0.5mg progesterone in order to examine female sexual behavior. The mean lordosis quotient (LQ) of the ARD group was 62.5±13.4. In the female control, SD and PRD groups, however, LQs were significantly lower than that of ARD rats, being 15.1±10.9, 37.5±14.7 and 23.8±11.8, respectively. These results suggest that the dorsal inputs to the POA and hypothalamus which pass anterior to the anterior commissure may exert an inhibitory influence not only on the female sexual behavior mediating system but also on the mounting mediating system in female rats.