Hippocampal and cortical activity during sexual behavior in the female rat.

Hippocampal and cortical activity were studied during sexual behavior in the female rat. Hippocampal theta appeared during her soliciting behavior. High-frequency theta accompanying the male's pursuit slowed when the male mounted the female and then increased in frequency during the brief continuation of lordosis following mounts without vaginal penetration. During prolonged lordosis after intromissions and ejaculations, slow theta continued. No changes in cortical frequencies were observed during mounts, intromissions, or ejaculations. During immobility (standing, sitting, and lying down) hippocampal activity became slow and irregular. High-amplitude hippocampal and, eventually, cortical spindles developed during immobility as sexual exhaustion was approached. Immobility and its accompanying electroencephalographic spindling are interpreted as indicative of a sexual satiety or inhibitory process.     

Role of the ultrasonic vocalization of the female rat (Rattus norvegicus) in sexual behavior

Both male and female rats vocalize ultrasonically during mating. Whereas male calls are known to facilitate female proceptive behavior, the female mating call has not been studied beyond spectrographic analysis. In this article, a series of experiments were done to examine the effects of the female's mating call on rat mating behavior. In the first experiment, females copulated with intact males before and after surgical devocalization. In the second experiment, intact females copulated twice with a male: once when they were able to hear and once when they were temporarily deafened with a medical ear mold. In the third experiment, tape recorded ultrasounds were placed in the presence of devocalized females while they were copulating with intact males. In the control condition, tape hiss was presented. In each experiment, it was observed that the female darted more if communication were disrupted (i.e., female devocalized or male deafened). Playback partially reduced darting to control levels. No other behavior was affected consistently across all experiments. Female calls might facilitate self-regulation of mating behavior, or they might focus the male's attention on her proceptive behaviors. It is also possible that the female calls could alter the stimulus properties of the male's behavior, indirectly affecting her own behavior.     

Role of monoamines in the control by hormones of sexual receptivity in the female rat.

The involvement of indole- and catecholamines in the hormonal regulation of sexual receptivity has been investigated in ovariectomized female rats. Drugs that reduce 5-hydroxytryptamine, dopamine, and adrenaline or increase noradrenaline neurotransmission tended to facilitate the occurrence of estrous behavior in estrogen-treated females, and drugs having opposite effects tended to inhibit receptivity induced by estrogen and progesterone. Estrogen decreased noradrenaline turnover in cortex and brain stem; progesterone enhanced this effect in brain stem but prevented it in cortex. Both hormones tended to block noradrenaline uptake in hypothalamus in vitro. In a schedule used to induce receptivity, estrogen accelerated serotonin turnover, an effect prevented by progesterone. Thus a number of monoamines may be involved in the control by hormones of estrous behavior. Furthermore, hormones affect both amine turnover and uptake mechanisms.     

Monoaminergic mediation of female sexual behavior.

Lordotic behavior was facilitated in estrogen-primed female rats by direct application of progesterone or serotonergic or beta-adrenergic receptor blockers to specific telencephalic, anterior hypothalamic-medial preoptic, or posterior hypothalamic sites. Blockade of the alpha-adrenergic system was ineffective in facilitating lordosis, as was the application of the active drugs to control sites in the thalamus or basal ganglia. Female soliciting behavior was not evoked by any of the treatments. It is concluded that the lordotic behavior component of the female rat's estrous behavior pattern is inhibited by a specific central monoaminergic system that also responds to progesterone. Soliciting behavior appears to be mediated by systems that are anatomically, and possibly neurochemically, separable from those regulating lordosis.     

Social isolation inhibits male-like sexual behavior in female hamsters

In the female golden hamster, Mesocricetus auratus, group housing permits the expression of male-like behavioral patterns including mounting and pelvic thrusting toward an estrous stimulus female. Sixty percent of females housed in groups of five showed these behaviors, while singly housed females were rarely observed to show mounting or thrusting. Females weaned at 19 or 35 days of age did not differ in their tendencies to show male-like behavioral patterns. Virtually all observations of mounting and pelvic thrusting behaviors were made on days when the females being tested were in behavioral estrus. These findings differ from previous studies which have reported that masculine behavioral patterns are rare in normal female hamsters. In previous studies females that were evaluated were typically not in behavioral estrus and were not housed for long periods of time with other intact females. Social factors interact with hormonal state to contribute to the expression of male-like behaviors in female hamsters.     

Hormonal control of sexual attraction in pseudohermaphroditic female dogs

Groups of female dogs exposed to different degrees of androgenic stimulation during development and a control group of ovariectomized females were tested for their attraction to tethered male and female stimulus animals. Attraction to the male was measured before and after administration of estradiol, and attraction to an estrous female was tested before and after administration of testosterone propionate (TP). Time spent visiting the tethered male was approximately equal for all groups prior to hormone treatment, but after receiving estradiol, control females exhibited a pronounced increase in visiting time; the second longest visits were paid by females that had received moderate amounts of androgen before birth; more heavily androgenized females exhibited no increase in attraction to the male despite estradiol injections. Visits to the estrous female before administration of TP were longer for some groups than for others, but there was no relation between the degree of perinatal androgenization and mean visiting time. After injections to TP the most pronounced increase in visiting was shown by females that had received the largest amounts of androgen during development, and the second largest increase occurred in the prenatally androgenized group. Control females showed the smallest increase in visiting time.     

Effects of female odors on the sexual behavior of male hamsters

A series of experiments was undertaken to investigate the effects of removal of several scent glands and scent-producing organs of female hamsters on the copulatory performance of male hamsters. In the first experiment it was shown that males engage in less copulatory activity toward females lacking vaginal secretions than toward females with these odors. Eliminating visual cues by observing pairs under infrared illumination did not change the performance of males toward these two kinds of females. The results of Experiment 2 indicated the importance of flank, ear, and Harderian glands as well as vaginal secretions--males showed the highest levels of copulatory behavior toward females with a full complement of odors and the lowest levels toward those lacking three of four sources of scent. Similar results were obtained in the third experiment in which anesthetized females were used as stimulus animals to increase the importance of chemical cues and to reduce variability due to the behavior of females. The sexual behavior of males was greatest toward females with all sources of scent present, lower toward those lacking vaginal secretions, and still lower toward those lacking vaginal secretions and other sources of odors. In the fourth experiment we asked whether any one of the nonvaginal scent glands was particularly important in stimulating male sexual behavior, but we found no differences in male performance toward females that lacked vaginal secretions or that in addition lacked one of the other scent glands. In the fifth experiment males displayed higher levels of sexual behavior toward vaginectomized females than toward vaginectomized females that had been deodorized by a cleaning procedure, again indicating the importance of nonvaginal odors in stimulating copulatory performance. Thus these experiments demonstrate the importance of vaginal secretions in the sexual arousal of male hamsters, a role for nonvaginal odors in sexual arousal of males, and the lack of necessity of these odors for male copulatory behavior. These results have implications for theories of olfactory communication in mammals and for interpretations of experiments in which lesions of the olfactory system lead to deficits in male copulatory performance.     

Estradiol and progesterone in the control of sexual receptivity in female rats

Estradiol (E₂) and progesterone (P) are both required for induction of sexual behavior in female rats under physiological conditions. Administration of E₂ in brief pulses can induce the behavior in ovariectomized rats. P does not normally exert inhibitory or anti-estrogenic effects on the behavior. The decline of sexual receptivity in ovariectomized E₂+P-treated rats is dependent upon the amount of E₂ and P given but independent on the continued presence of either hormone. Ovariectomized animals treated with a constant amount of E₂ show a behavioral rhythm which is disrupted by hypothalamic lesions and it is suggested that peptidergic neurons in the suprachiasmatic nuclei of the hypothalamus rhythmically inhibit the behavior of ovariectomized E₂-treated rats.     

Central progesterone induces female sexual behavior in estrogen-primed intact males rats

Progesterone induced high levels of female lordotic behavior in 10 of 17 intact, estrogen-primed male rats when it was applied directly to the medial preoptic-anterior hypothalamic area. All 17 males previously had shown lordosis when the serotonergic antagonist methysergide was applied to the same central sites. Few males responded to systemic progesterone and none to intracralial cholesterol. Intradiencephalic Metycaine, a local anesthetic, induced lordosis in eight male that previously had responded to central progesterone. These data indicate that estrogen and progesterone act synergistically to induce lordosis in male rats when progesterone is administered directly to sensitive brain sites.