Effects of neonatal treatment with cyproterone acetate on aggressive behavior induced by footshock in adult male rats

High levels of androgens are required to organize aggressive behavior in adult male rats. Footshock-induced aggression was tested in Wistar rats allocated to one of three experimental groups: control (oil-injected) males (M), males neonatally injected with the antiandrogen cyproterone acetate (CA), and males treated as in the CA group but gonadectomized just before puberty (CAG). An antiaggressive effect of CA in those adult male rats neonatally treated with this compound was found. Neonatal exposure to cyproterone acetate exerts an antiandrogenic effect over the expression of shock-induced aggressive behavior. The behavioral effects of CA were not countered by adult treatment with testosterone propionate.     

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.     

Comparison of agonistic behavior in individually-housed male mice with those cohabiting with females

Videotape recordings of male mice group-housed, individually-housed and cohabiting with females, were rated for their agonistic behavior in a “standard opponent” test. Previously mated male mice showed more fighting than isolated or grouped males. Marked differences in other social and non-social behaviors, which could not be accounted for in terms of increased fighting, were not evident. These results suggest that agonistic behavior may be usefully studied by examining male mice that have cohabited with females. One obvious advantage is that such mice cannot be dismissed as being “socially deprived,” as is sometimes claimed for individually-housed mice. Other advantages are that aggressiveness is induced quickly, at high levels, and the mice appear very sensitive to hormone manipulation following castration.     

Neonatal androgenic stimulation and adult sexual behavior in male and female golden hamsters.

Neonatally and adult castrated male hamsters as well as neonatally androgenized and nonandrogenized female hamsters were tested for both mounting and lordosis behaviors during treatment with either testosterone or ovarian hormones. Neonatal androgenization facilitated mounting behavior in adult animals administered either testosterone or ovarian hormones and suppressed lordosis behavior in adult ovarian-hormone-treated animals. Early androgen effects on the display of lordosis behavior during adult testosterone treatment were complex and varied with the exact timing of perinatal endogenous or exogenous androgenization. Species differences in hormone-behavior relationships and the possible role of perinatal androgenization in the development of rodents' ability to aromatize androgens were discussed.     

The role of endocrines in isolation-induced lntermale fighting in albino laboratory mice. II. Sex steroid influences in aggressive mice

Isolation-induced intermale fighting in laboratory mice can be dramatically reduced under most circumstances by castration. This behavior in castrates may, however, be restored, or even accentuated, by androgen replacement. Experiments on the effects of sex steroids on such fighting in castrated mice, which, for want of a better term, are designated as “aggressive,” have been recently described. These mice are housed with a female until 10 days after siring a litter and are, thereafter, housed individually for a further 14 days before castration and subsequent hormone treatment. Such mice show substantial levels of fighting in “standard-opponent” tests even before isolation. Although castration results in reduced fighting in these mice, this behavior is rarely completely abolished in all individuals. It seems likely that steroid treatment of aggressive mice maintains or intensifies an already present motivation. Treatments in these studies consisted of daily oil-based intramuscular injections for 14 days preceding and throughout behavioral testing. The standard-opponent tests were 7 min encounters with adult, subordinate, grouped males in the cleaned home cages of experimental mice. The steroids investigated included estradiol benzoate (EB), 19-hydroxytestosterone (19-OHT), androstenedione (A), testosterone (T), and Sα-dihydrotestosterone (DHT), either singly or in combination. The results suggest that (a) on a dosage basis, estrogens were at least as effective as androgens in maintaining fighting in castrated aggressive mice; (b) 19-OHT (one of the metabolic intermediates between testosterone and 17 β-estradiol) was also effective but somewhat less so than the same dose of EB; (c) the three naturally occurring androgens investigated all effectively maintained fighting at comparatively low doses (50 μg/day) which compares with a replacement dose of 500 μg/day of T in some studies in traditional castrated mice (e.g., Luttge and Hall, 1973); (d) aromatization is not essential for a behavioral action of androgens as DHT, a nonaromatizable androgen, maintained fighting in these mice; (e) whereas a two-site (central motivational and peripheral penile) action seems probable in the influence of androgens on sexual behavior in castrated rats (e.g., Parrott, 1975), DHT did not augment the action of EB on fighting in castrated aggressive mice, indicating that only a central action of steroids was required in the aggressor.     

Rare male aggression directed toward females in a female‐dominated society: Baiting behavior in the spotted hyena

Spotted hyenas (Crocuta crocuta) are gregarious carnivores. The females are socially dominant to males, and adult males rarely direct aggression toward adult females. This study analyzed all cases in which adult immigrant males behaved aggressively toward adult females in a large population of free‐living hyenas in Kenya, observed for 11 years. Our goals were to describe the conditions under which male attacks on females occur, and address possible adaptive functions. Most aggression directed by adult immigrant males against females occurred when coalitions of two or more males attacked a single adult female, who typically responded by defending herself and fighting back. Male aggression against females frequently occurred at sites of ungulate kills, but males never behaved aggressively toward females over food, and all male attacks on females were unprovoked. Although no mounting or other copulatory behaviors ever occurred during or immediately after an attack, the number of male attacks on females peaked around the time of conception. Daily rates at which males attacked females did not vary with female social rank. However, daily attack rates did vary significantly with female reproductive state, and the highest rates of male attack on females were observed during the two stages of the reproductive cycle during which females were most likely to conceive litters. The adaptive significance of male aggression against females in this species remains unknown, but a tight association between male attacks on females and a female's time of conception provides strong evidence of some role for male aggression in hyena sexual behavior. In particular, our data are consistent with hypotheses suggesting that male aggression toward females in this species either serves to inform females about male fitness or represents sexual harassment. Aggr. Behav. 29:457–474, 2003. © 2003 Wiley‐Liss, Inc.     

Variation in aggressive behavior and anatomo-physiological correlates generated by crowding without physical contact in the house mouse

Behavioral, physiological (i.e., endocrine), and anatomical consequences of crowding in mice were studied in a situation where animals were in auditory, visual, olfactory, and tactile contact but restrained from full physical interactions, to prevent overt aggression. Males that cohabited with females undisturbed by neighboring conspecifics showed greater propensity to attack same-sex intruders and had higher plasma testosterone levels than did their “crowded” counterparts, that is, males cohabiting with females and housed adjacent to other male/female pairs. In this respect, the latter animals resembled submissive males. However, a significant increase in weight of androgen-dependent target organs (i.e., seminal vesicles and preputial glands) was found in crowded males. These data indicate that despite the observed inhibition of social aggression these males are not physiologically comparable (homologous) to male mice that experienced defeat and the stress of submission during fighting. The intriguing possibility that different conversion pathway of testosterone are accelerated, as a result of social communication, in males living in these two environments and the behavioral implications of these possibilities are discussed. Finally, the parental behavior of crowded animals, although not freely interacting with each other, was disrupted, causing a marked decrease in reproductive success. In this situation a high incidence of infanticide of their offspring by both parents was observed, whereas this behavior was virtually absent in non-crowded male/female pairs.     

Television and Sex-Role Stereotyping1

The possible influence of television on sex-stereotyped behavior was investigated in three studies. In Study I the portrayal of male and female central characters on children's Saturday morning television programs was examined, and a number of differences consistent with current sex-role stereotypes were found. Males and females were portrayed in different roles, they manifested different behaviors, and their behaviors were followed by different consequences. In addition, male characters were more frequent than females, and they exhibited higher rates of behavior. Similar differences in the portrayal of males and females in the commercial announcements accompanying these programs were found in Study II. The sexes differed in their frequency of appearance, their location, their roles, their expertise, and the consequences of their behavior. In Study III the effects on children's behavior of exposure to sex-stereotyped vs. non-stereotyped behavior by adult televised models were examined. It was found that children manifested greater imitation and recall for the behavior of a same-sex model with the result that boys exposed to “stereotyped” behavior by a male and female model manifested and recalled relatively more “masculine” behavior than those exposed to “non-stereotyped” behavior, while the opposite trend obtained for girls. Implications of these three studies for television's contribution to sex-stereotyped behavior are discussed.     

Genotype modulates prenatal stress effects on aggression in male and female mice

Prenatal stress (heat and restraint) significantly increased postpartum aggression (proportion of animals fighting and/or the intensity of the behavior) in C57BL/6J female mice and reduced the behavior in DBA/2J females. For intermale aggression, prenatal stress increased the behavior (intensity of aggression) in C57BL/6J males but did not affect aggressive behavior in DBA/2J animals. Infanticidal behavior (the killing of young) exhibited by male mice was not influenced by prenatal stress in either strain. Relative anogenital distance measurements in neonates at birth did not serve as a reliable predictor of strain variation in prenatal stress effects. Prenatal stress did not influence this measure of prenatal androgen exposure in DBA/2J or C57BL/6J females. For males, prenatal stress elevated relative anogenital distance in C57BL/6J mice and decreased this measure in DBA/2J animals. Prenatal stress effects on aggressive behavior in male and female mice therefore depend upon genotype. Strain-dependent differences may be modulated by differences in endocrine reactivity to prenatal stress/and or differential central neural tissue sensitivity to hormones.     

Male-female differences and the influence of neonatal and adult testosterone on intraspecies aggression in rats.

Male and female albino rats were tested for intraspecies aggression without the use of shock. In the first experiment, male pairs showed more biting attacks, offensive sideways movements, and self-grooming than did female pairs; male pairs also showed more stereotyped defensive/submissive behaviors and were wounded more frequently. The second experiment examined the effects of neonatal castration and testosterone propionate (TP) administration on fighting. Males castrated at birth attacked other males less frequently than did controls when tested with TP treatment as adults. The TP given at birth to neonatally castrated males restored attacks to control levels. Females given TP as neonates did not differ from either male or female controls. Other aggressive/defensive behaviors, however, did not show this pattern. The results suggest that while the presence of testosterone during a brief postnatal period and during adulthood is necessary for attack behavior to occur, other related behaviors may not be affected in a similar manner.     

Role of neonatal androgens in sexual differentiation of brain structure, scent marking, and gonadotropin secretion in gerbils

Gerbils display a sexually dimorphic scent marking behavior that responds to testosterone (T) in adulthood and develops under the influence of testosterone perinatally. A complex of cell groups between the preoptic area and anterior hypothalamus of the gerbil brain is also sexually dimorphic and responsive to testosterone. One of these cell groups, the sexually dimorphic area pars compacta (SDApc), usually exists only in males. Even when given testosterone, adult female gerbils rarely have an SDApc. To determine if the SDApc develops under the influence of testosterone, male gerbils were castrated or given sham operations on the day they were born or 1 day later, or were not manipulated. Female gerbils were injected subcutaneously with 0, 50, or 100 micrograms testosterone propionate (TP) on the day after birth. When given ovarian transplants as adults, neonatally castrated males scent marked at low levels typical of females. Neonatally androgenized females given testosterone as adults scent marked at high levels typical of males. Neonatal castration did not affect the probability that the SDApc would develop, but neonatal androgenization did. Half the females given either dose of TP as neonates had SDApcs bilaterally. The sizes of the SDApcs present in females depended on the dose of testosterone given neonatally. The larger dose produced larger SDApcs. The 100-micrograms dose of TP also defeminized gonadotropin secretion, but the 50-micrograms dose did not. The castration of males neonatally prevented the defeminization normally caused by endogenous testosterone. Both groups of neonatally castrated males formed corpora lutea in their ovarian transplants, but control males did not.     

The expression of the genes of aggressiveness in mice: The effect of androgen on aggression and sexual behavior in females

Female mice of strains selectively bred for aggressiveness or nonaggressiveness were injected with testosterone propionate (TF′) at the age of 2 days and as adults, or they were injected as adults only. Aggressive and sexual behavior was then tested with female, receptive female, and male partners before, during, and after the latter TP treatment. The females that had received both TP treatments displayed as much or as little aggression as males of the same strain, leading to the conclusion that aggressiveness genes are not linked with the male sex chromosome, even though they depend on it for their expression. The sexual behavior of the females of both strains that had received both TP treatments was altered to the male type. In the females of the aggressive strain even adult treatment alone was sufficient for this change. Aggressiveness and male sexual behavior would seem to be determined separately, although aggressiveness facilitates the display of male sexual behavior.     

Sex-role behavior and obedience to authority: A field study

Obedience by male and female subjects to male and female experimenters was investigated under various conditions of “perceived legitimacy.” The procedure involved an experimenter stopping a subject who was about to cross a street at a particular crosswalk, the subject was then instructed to cross at another designated location. The dependent variable was the level of obedience to these instructions. The four main factorial independent variables were the sex of the experimenter, the sex of the subject, and two conditions of “perceived legitimacy” (presence or absence of a “uniform,” presence or absence of an “explanation”). Significant results were obtained for the uniform and sex of subject main effects (more obedience with a uniform, more disobedience by females). Additional analyses indicated that “older” subjects disobeyed more often than “younger” ones, that “formally” dressed subjects disobeyed more often than “informally” dressed ones, and that ethnic minority group experimenters were disobeyed significantly more often than Caucasian experimenters. Significant interactions were also obtained, mainly due to the behavior of the younger men and the older women. Male and female experimenters were obeyed equally, in general. The results are discussed in relation to sex-role prejudice and discriminatory behavior.     

Psychopharmacological therapy of deviant sexual behavior

Psychopharmacological approaches to controlling male deviant sexual behavior, especially sexual recidivism and sexual deviants on probation, have been reported in psychiatric literature. In Europe, the drug cyproterone acetate, and in the United States, medroxyprogesterone acetate, Provera, and in the long-acting form, Depo-Provera, have all benefitted exhibitionists and pedophiliacs, and reduced sex drive in sexual deviants. The combination of pharmacotherapy and either psychotherapy or behavioral therapy has been the most effective approach to reducing the sex drive of sexual deviants.     

The effect of vicarious punishment on prosocial behavior in children

Two experiments are reported dealing with the effects of vicarious punishment on prosocial behavior. In Experiment I, first and second grade females who witnessed a peer model being punished for a refusal to share (“nonsharing, punished”), shared more than an appropriate control group. Sharing was similarly heightened, however, in a group who witnessed punishment to the model which was not contingent upon any specific behavior (“punishment only”). Experiment II tested and confirmed the hypothesis derived from Experiment I that noncontingent vicarious punishment has a generalized inhibitory effect on antisocial behaviors. First, second, and third grade females were shown either the “nonsharing, punished,” “punishment only,” or baseline videotapes used in Experiment I. Subsequent to viewing the tapes, subjects in the “punishment only” condition helped the experimenter significantly more than did subjects in the “nonsharing, punished” and baseline conditions. The ability of existing theoretical treatments of vicarious punishment to account for these results is questioned.     

Ethanol effects on shock-induced fighting and muricide by rats

Ethanol (0.25-1 gm/kg body weight; IP) did not significantly alter shock-induced fighting, regardless of whether it was administered to both rats or to only one rat of the pair. Higher doses tended to decrease shock-induced fighting. Ethanol (0.25-2 gm/kg body weight; IP) also did not induce “nonkiller” rats to kill mice and only high doses (1.5 and 2 gm/kg body weight) decreased the incidence of muricide in “killer” rats. The depressant effects of ethanol on both shock-induced fighting and muricide appeared to result from drug-induced ataxia rather than from a direct effect of ethanol on aggressive behavior.     

Activity of creatine kinase in mice under various “Stress” conditions

“Stress” induced by swimming, immobilization, and fighting in male albino mice results in a significant increase of creatine kinase (CK) activity in blood obtained by decapitation. The increase partially depends on motor activity as shown in fighting animals. Males show higher CK values than females. Isolation and even immobilization also lead to higher CK activity, the latter to a similar extent as swimming and fighting. We believe that CK activity is regulated by processes additional to motor activity.     

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.     

Perceptions of sexual harassment as a function of sex of rater and incident form and consequence

The purpose of this study was to investigate differences in perceptions of two “severity dichotomies” present in the Equal Employment Opportunity Commission Guidelines on sexual harassment. Alale and female undergraduates (N = 198), from a predominately white midwestern university, were given one of four statements based on these guidelines, varying “form” (physical/verbal) and “consequence” (economic injury/hostile environment) of the behavior. Analysis of variance results showed females rated the incident as more definitely sexual harassment and as affecting perfonnance more than did males. Participants reading “economic injury” statements rated them as having more effect on the victim’s job status than did those reading “hostile environment” statements. A multivariate analysis of variance revealed significant “consequence” and “sex” effects on several factors: A significant three-way interaction showed that males rated statements less negatively than did females, especially when the statement described “physical” behavior with “hostile environment“ consequences. Cluster analysis results are also presented.     

Attitudes in four age groups toward sex role division in adult occupations and activities

Kindergarten, eighth grade, college, and adult subjects were presented with a list of 43 adult occupations. They indicated for each whether it should be performed by a male, female, or either. Liberality, defined in terms of the number of “either” responses, increased markedly from kindergarten to eighth grade through college and then showed a moderate decrease in the adult sample. In each age group except kindergarten there was a significant sex difference with females being more liberal. Analysis of individual roles showed that both sexes were willing to let women into prestige occupations but females were more willing than males to have household and child-caring tasks performed by both sexes.