Aggressive behavior in female hamsters: the hormonal basis for fluctuations in female aggressiveness correlated with estrous state

The frequency and sequencing of aggressive behaviors by naive female hamsters change during series of brief encounters, probably because of the lack of stable dominance relations. Such initial encounters seem most representative of interactions likely in free-ranging hamsters and have been emphasized in studies of the hormonal mediation of female aggression. Nonestrous females exhibit intense aggression toward conspecifics of either sex. Estrous females are not aggressive and spend much time in lordosis, indicative of sexual receptivity. The inhibition of fighting on estrous day depends on estrogen and progesterone. Whereas oil-injected adrenalectomized-ovariectomized females fight at high levels, comparable with intact nonestrous females, the combination of 17 beta-estradiol benzoate and progeterone suppresses fighting completely. In contrast, replacement of estradiol, progesterone, or testosterone propionate individually has on consistent effect. Hypophysectomized females also fight at high levels, indicating that pituitary hormones are not required for vigorous aggression. Further, individual anterior pituitary hormones did not produce marked changes in fighting. These results emphasize the roles of estrogen and progesterone in synchronizing aggression with current reproductive state.     

Effect of novel and familiar mating partners on the duration of sexual receptivity in the female hamster

The lordosis duration of the female golden hamster (Mesocricetus auratus) in response to novel and familiar mating partners was examined. In Experiment 1, females mated to the point of sexual satiation with one male hamster, and following its removal, showed renewed receptivity in response to the introduction of a second male. Upon sexual satiation with the second male, females either received a novel third male or were reexposed to the original male. Total lordosis duration in the third bout in the group receiving a novel male was significantly greater than in the group reexposed to the original male. In Experiment 2, the insertion of a 1-h delay between the second and the third mating partner had no effect on the female's responsiveness, regardless of whether the third male was the original male or a novel male. In Experiment 3, removal of the ovaries followed by hormone replacement treatment (40 micrograms estradiol benzoate, 72 h prior to testing, and 500 micrograms progesterone, 4 h prior to testing) failed to alter the females' ability to discriminate between novel and familiar mating partners. These results demonstrate that females make clear discriminations among individual mating partners, that this can affect sexual receptivity and will continue to do so following a delay of at least 1 h, and that the effect is not mediated by the release of ovarian steroids.     

Unconditioned sexual incentive motivation in the male Norway rat (Rattus norvegicus)

Sexual incentive motivation was evaluated in a procedure consisting of a large open field where incentive animals were confined behind wire mesh openings. When sexually inexperienced male rats (Rattus norvegicus) were exposed to the receptive female-male incentives, they spent more time close to the female. If the incentives were receptive female-nonreceptive female, the receptive female was preferred. However, when the alternatives were nonreceptive female-male, no preference was obtained. Castration abolished preference for the receptive female, and treatment with testosterone propionate restored it. Estradiol plus oil is as efficient as estradiol plus progesterone for giving the ovariectomized female incentive properties. The living female can be replaced with female odor. Sexual experience did not have any long-term effects on the female's incentive value, but immediately preceding limited sexual activity enhanced it     

Social variables influence female sexual behavior in the musk shrew (Suncus murinus)

The role of social variables in the mediation of sexual behavior was examined in the female musk shrew (Suncus murinus). Two social variables were manipulated: amount of reproductive experience and exposure to male-related chemical cues. Virgin females took significantly longer to achieve receptivity than did sexually experienced females. In addition, exposure to soiled bedding taken from a male's cage for 24-hr prior to testing reduced receptivity latencies in all females. Even a brief (30 min) exposure to male-related cues was effective in facilitating receptivity in virgins. The converse was noted for female aggressive behavior. Virgin females attacked more frequently than experienced females, and preexposure to male-related cues reduced aggressiveness. These findings suggest that social variables play an important role in female sexual behavior in this primitive eutherian mammal.     

Inhibition of aggression by progesterone and its metabolites in female Syrian hamsters

The sequence of estradiol and progesterone is known to inhibit the expression of aggression in female hamsters. Despite the key importance of progesterone in the inhibition of aggression, little is known of the mechanisms through which progesterone may exert this effect. Three experiments were performed to assess the degree to which metabolites of progesterone can affect aggression in female Syrian hamsters. Systemic estradiol treatment followed by injections of either progesterone (300 μg IP) or 4‐pregnen‐21‐ol‐3,20‐dione (DOC, 300 μg IP) reliably inhibited aggression. Systemic injection (75, 150, or 300 μg IP) of either 5α‐pregnan‐3α,21‐diol‐20‐one (THDOC) or 5α‐pregnan‐3α‐ol‐20‐one (3α,5α‐THP) did not affect aggression. Intracerebroventricular infusion of 3α,5α‐THP following systemic estradiol treatment also did not affect aggression. In a third experiment, female hamsters were given systemic treatments with estradiol and progesterone that were subthreshold with respect to inhibition of aggression. In these females, intracerebroventricular infusion of THDOC inhibited aggression. These results indicate that metabolites of progesterone can inhibit aggression, most notably in synergy with progesterone itself. Aggr. Behav. 27:372–381, 2001. © 2001 Wiley‐Liss, Inc.     

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.     

Maternal aggression toward infanticidal males of different social status in wild house mice (Mus musculus domesticus)

Maternal aggression was examined in wild female mice (Mus musculus domesticus) derived from animals trapped in Alberta, Canada. Lactating females were tested for their behavior toward intruder males during the time of postpartum estrus while housed in a two-cage apparatus containing a defensible nest area. Prior to being used as intruders, sexually naive males were screened for their behavior toward a newborn pup (83% exhibited infanticide). Only infanticidal males were then housed in pairs and allowed to establish a dominance hierarchy. Dominance status was further verified by a urine marking test. The dominant and subordinate infanticidal males were then placed into a lactating female's cage and observed for 1 hr. The test was terminated immediately when a male began to attack the pups. Lactating females attacked the males in both groups, but subordinate males received more intense attacks than dominant males. Dominant males elicited significantly more fear/defense behavior than subordinate intruders. All of the dominant males and only one submissive male attacked the pups. Females were thus successful in blocking infanticide only by infanticidal subordinate males. Since females do not persist in attacking males with high fighting ability, one function of maternal aggression could be to assess the fighting, and resource holding, potential of a future mate. © 1994 Wiley-Liss, Inc.     

大学生性别情绪刻板印象的内隐和外显研究

为了了解不同性别大学生的性别情绪刻板印象,并分析内隐和外显测验的关系,对280名大学生进行了外显连线测试,对87名大学生进行了内隐联想测验。结果发现:在内隐和外显测验中,男女大学生均存在性别情绪刻板印象,将男性名字更多地与愤怒词相联系,将女性名字更多地与高兴词相联系;男女大学生的性别情绪刻板印象程度存在极其显著的差异,女生更明显地表现出"男性更容易愤怒、女性更容易高兴"的偏见;被试的内隐和外显性别情绪刻板印象相关不显著,是两个不同的建构。     

Evidence that a factor besides progesterone, prolactin, or plasma-estradiol-binding protein inhibits estrogen-induced sexual receptivity in pregnant rats.

Daily administration of estradiol benzoate stimulated significantly less lordotic behavior in rats during the second half of pregnancy than in ovariectomized females that received subcutaneous progesterone implants, pituitary grafts that raised plasma prolactin, or both treatments combined. Following an initial facilitation of receptivity, females with progesterone implants showed only moderate reductions in lordosis quotients over 3 test days. The capacity of plasma from pregnant rats to bind estradiol was found to increase significantly during the second half of pregnancy. However, daily administration to pregnant rats of a synthetic estrogen, R 2858, which is not bound by plasma protein, was no more effective than estradiol benzoate in stimulating receptive behavior. Administration of estradiol benzoate also stimulated significantly lower levels of sexual behavior in pregnant females than in females in which pseudopregnancy had been prolonged by previous hysterectomy or induction of uterine decidualization. These findings suggest that some endocrine factor other than progesterone, prolactin, or estradiol-binding protein is primarily responsible for the potent suppression of behavioral responsiveness to estrogen which occurs in pregnant rats. It is suggested that 5 alpha-reduced androgens may cause these behavioral effects.     

Sociosexuality and face perception: Unrestricted sexual orientation facilitates sensitivity to female facial cues

Across two studies, sexually unrestricted men and women showed heightened sensitivity to female facial symmetry (a signal of genetic fitness) and female sexual receptivity (happy facial expressions). In Study 1, individuals assessed the attractiveness of male and female targets of varying facial symmetry. Sexually unrestricted men and women, compared to their sexually restricted counterparts, showed a stronger symmetry advantage in attractiveness ratings for female targets, an indication of greater sensitivity to facial symmetry. Study 2 asked participants to discriminate between genuine (Duchenne) and deceptive smiles on both male and female faces. Results indicated that sexually unrestricted men and women, compared to sexually restricted individuals, were better able to discriminate between these actual and deceptive signals of receptivity for female targets. Neither study found any relationship between sociosexual orientation and the perception of male targets. These results suggest that sexually unrestricted individuals are attuned to reproductively-relevant cues in female faces.     

Effect of anosmia on reproduction in male and female wolves (Canis lupus)

Anosmia was produced in two female and three male wolves by transection of the olfactory peduncle and was confirmed by their inability to detect meat, urine, feces, anal-gland secretions, and fish emulsion. All operated animals continued to investigate the environment with their noses, to interact normally with other pack members, and to feed at levels which maintained presurgical body weights. No effect was found on reproductive physiology (females: estradiol or progesterone concentrations, ovulation, pregnancy or parturition; males: testosterone, testicular recrudescence or sperm numbers, motility or maturation). One anosmic female became dominant and although she urine-marked with a flexed leg, the rate was lower than typical for dominant females and perhaps contributed to her failure to pair-bond with the dominant male. One anosmic male raised-leg-urinated while competing for pack dominance and when kenneled away from other males. Precopulatory, copulatory, and maternal behavior were observed for one anosmic female and appeared normal. However, neither male that was sexually naive before surgery showed interest in proestrous or estrous females. The possibility that secondary degeneration of brain regions mediating sexual behavior was responsible for the failure of these males to respond was not supported. Not only was the lack of male sexual response the only serious deficit following transection, but the male which was sexually experienced prior to surgery did copulate successfully during his second postoperative breeding season despite continued anosmia. Chemosensory priming from female urine during the protracted proestrous phase, as well as urinary and vaginal odors during estrus, appear to be critical for induction of full sexual potency in sexually naive males. The importance of urine and vaginal secretions in the sexual response of experienced males is uncertain.     

Female lordotic behavior mediated by monoamines in male rats.

Direct application of serotonergic of beta-adrenergic receptor blockers to anterior or posterior areas of the hypothalamus induced lordosis in intact estrogen-primed male rats. Such treatment with an alpha-adrenergic blocker or systemic administration of progesterone failed to increase lordosis. Centrally elicited lordosis did not occur without estrogen priming. Anatomical and neurochemical similarity may exist in the brain mechanism mediating lordotic behavior in male and female adult rats.     

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.     

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.     

Factors affecting incidence of infanticide and discrimination of related and unrelated neonates in male Mus musculus

Infanticide by males was examined in two strains (C57B1 and DBA) of the house mouse (Mus musculus). Males that had contact with a female within the previous 2-3 weeks rarely committed infanticide when introduced to the home cage of a female and her 1-day-old neonates, even when the female and neonates were of a different strain and from a different colony. In contrast, 90% of C57B1 males that had no contact with a female for more than 7 weeks killed pups when placed in the female's home cage, and 60% killed when a 1-day-old pup was introduced to the male's home cage. No difference in levels of infanticide occurred when grouped males were compared to isolated males. These results indicate that infanticide is not dependent upon recognition of the pups or the female, but depends on the male's previous exposure to females. Infanticidal behavior is not directly determined by genetic relationship, but the factors that inhibit this behavior reduce the probability that a male will kill his own offspring.     

Female behavior in populations of mice in the presence and absence of male hierarchy

Female aggression may be the regulator of population size in small mammals. Freely growing populations of house mice showed several differences in aggressive female behavior in the presence and the absence of a male hierarchy. Territoriality in females and not in males appeared to maintain social order and regulate population density. Certain females were seen patrolling and guarding the territory and chasing and fighting with both male and female intruders. These females did not fight amongst themselves, suggesting that they were not fighting for rank (as do the males) but for territory. Although these aggressive females produced young, the pups were neglected, and few were weaned. The non-aggressive females were the successful breeders. Aggression by the females only occurred when there was reproduction and increased densities. Assembled females with no males present never show this aggression. The occurrence of “male-type” behavior became most apparent when the males were removed at peak population densities. The removed males were then castrated and injected with testosterone cyprionate. Doses were increased by population cage, and therefore all males returned to each freely growing population were given the same dose. The males given oil placebo injections showed no return of a male hierarchy and the females showed high levels of aggression toward them. Males injected with testosterone cyprionate showed return of male aggression and fighting and mounting of females. But the new “dominant” females continued their patrols and chased males away from their territories and did not permit these males to mount. Male-male fighting consisted primarily of frontal attacks to the face and roll and tumble fights. Female-male aggression consisted primarily of attacks to the posterior region targeted at the base of the tail and the genitals of the male. The males were rarely seen attacking females and then only during mating. Females only attacked each other in defense of their territories.     

Vaginal stimulation in rats induces prolonged lordosis responsiveness and sexual receptivity.

Sexual receptivity to males resulted from stimulation of the vagina with a glass rod in previously unreceptive ovariectomized, estrogen-treated rats. Several minutes of rejection behavior preceded the receptivity. In a second study, manual palpation was used to determine the duration of the lordosis response facilitation. Initially, all females were unresponsive to manual flank-perineum stimulation (palpation). Vaginal stimulation plus palpation, which together elicit lordosis, facilitated subsequent lordosis responses to palpation. This effect persisted for several hours after the vaginal stimulation was applied. Vaginal stimulation alone, which was ineffective in eliciting lordosis, also facilitated lordosis in response to subsequent palpation. Repeated palpation did not facilitate lordosis. These prolonged effects were independent of hormone treatment.     

Opposite strain-dependent differences for intermale aggressive behavior elicited by individual housing and housing with a female in the mouse

Male mice of the C57BL/6 strain show a significant increase in aggression toward a nonaggressive male conspecific following 72 hr of individual housing. However, this increase was no longer evident following 2 weeks of individual housing. When housed with a female, C57BL/6 mice show significantly more aggression than singly housed mice of the same strain after 72 hr as well as 2, 4, 8 weeks of differential housing. Male C57BL/6 mice housed with a female also show significantly higher levels of aggression than DBA/2 mice living in the same housing condition after 4 or 8 weeks of differential housing. Finally, male DBA/2 mice individually housed for 8 weeks are significantly more aggressive than mice of the same strain housed with a female for the same time. These results indicate that the increase in aggressive behavior observed following isolation and cohabitation with a female in the mouse is not the same phenomenon. © 1994 Wiley-Liss, Inc.     

Fear of success versus fear of gender-inappropriate behavior

To test the prediction that both males and females would show evidence of fear of success when success was achieved in a nontraditional field, male and female subjects wrote five-minute stories in response to cues depicting a male's or female's success in medical school or nursing school. Results showed that both sexes wrote more fear of success stories in gender-inappropriate than in gender-appropriate conditions. The need for a broader conception of fear of success motivation is discussed.Portions of this paper were presented at the meeting of the Midwestern Psychological Association, Chicago, May 1975.     

Male versus female Siamese fighting fish as reinforcing stimuli for conspecific males in single- and two-choice operant situations

Two experiments attempted to determine the reinforcing effectiveness of visual exposure to a female versus a male stimulus in male Siamese fighting fish (Betta splendens). This was accomplished by making male or female presentation contingent upon an operant ring swimming response in single- (Experiment 1) and two-choice (Experiment 2) continuous reinforcement operant situations for 1 hr per day. It was found that visual exposure to a female stimulus was behaviorally reinforcing in a way comparable to that typically found in intermale studies. If given a choice, male test subjects were observed to demonstrate a consistent preference for the female as opposed to the male stimulus. The results are discussed in terms of stimulus discrimination and approach-avoidance conflict as differentially elicited by male and female target stimuli.