Effects of sympathetic inhibition on receptive, proceptive, and rejection behaviors in the female rat.

The present investigation was designed to examine the effects of sympathetic nervous system (SNS) inhibition on sexual behavior in ovariectomized, steroid-treated female rats. Clonidine, an alpha2-adrenergic agonist, guanethidine, a postganglionic noradrenergic blocker, and naphazoline, an alpha2-adrenoreceptor agonist were used to inhibit SNS activity. Intraperitoneal injections of either 33 micrograms/ml or 66 micrograms/ml clonidine significantly decreased receptive (lordosis) and proceptive (ear wiggles) behaviors and significantly increased rejection behaviors (vocalization, kicking, boxing). Either 25 mg/ml or 50 mg/ml guanethidine significantly decreased receptive and proceptive behavior and had no significant effect on rejection behaviors. Naphazoline significantly inhibited lordosis behavior at either 5 mg/ml or 10 mg/ml doses, significantly inhibited proceptive behavior at 5 mg/ml, and had no significant effect on rejection behaviors. These findings support the hypothesis that SNS inhibition decreases sexual activity in the female rat.

Adrenal role in proceptivity and receptivity induced by two modes of estradiol treatment.

The effects of chronic estrogen treatment on the receptive and proceptive behaviors of the female rat were investigated using two modes of estrogen administration: estrogen implants and chronic estrogen injections. In addition, the potential mediating role of the adrenal was investigated. Animals were either ovariectomized (OVX) or ovariectomized and adrenalectomized (ADX-OVX). Each surgery group received three doses of estrogen, via implants in Experiment 1 and chronic injections in Experiment 2. Each animal was tested with and without progesterone treatment. Within the range of doses in the two experiments, the effect of estrogen on proceptivity appeared to be dose dependent. However, low estrogen doses were sufficient to maintain a high level of receptivity. These results suggest different mechanisms for the induction of proceptive and receptive behavior in the female rat. The facilitatory effect of progesterone on receptivity was dependent on the estrogen dose for both modes of administration, but on proceptivity was dependent on the estrogen dose only following chronic estrogen injections. Overall, this study suggests that the adrenal gland is important in the display of female sexual behavior elicited by exogenous hormones. The estrogen implant study (Experiment 1) revealed that while the adrenal gland is not necessary for receptive behavior, it is important for the display of proceptive behavior. In addition, with chronic estrogen injections (Experiment 2), progesterone was more effective in elevating proceptivity in ADX-OVX than in OVX females, and ADX-OVX females treated with progesterone generally showed less lordosis behavior than OVX females treated with progesterone. These results suggest that progesterone of adrenal origin may be important for sexual responding in the female rat.

Aggression by a female rat cohabitating with a sterile male: termination of pseudopregnancy does not abolish aggression.

At the end of that time, each female was assessed for aggressiveness toward an unfamiliar female intruder once each week for 3 weeks. Those females displaying a high level of aggression had their male cagemate changed. For half of the females, the new male cagemate was a castrated male with a testosterone implant. For the other half, the new cagemate was a castrated male without a testosterone implant. Replacement males had been subjected to surgery 9 weeks previously. There were no differences in the aggressiveness of females of the two groups on any of 3 subsequent weekly tests of aggression. In a 3-h evaluation of male sexual behavior, none of the 9 castrated males without testosterone replacement displayed sexual activity with an estrogen/progesterone primed ovariectomized female, but 6 of 9 males with testosterone replacement did. Reanalysis of the aggression data comparing the females whose males had no testosterone replacement and females housed with the 6 males that were sexually active also revealed no differences in aggression over the 21-day test period. Since pseudopregnancy is known to last 13 days, these results indicate that the continuous presence of pseudopregnancy is not required for maintenance of aggression by a female cohabiting with a sterile male.