Effects of early exposure to mating on adult sexual behavior in male mice varying in their genetic disposition for aggressive behavior

This study examined whether the sexual behavior of adult male mice is influenced by exposure in early postnatal life to brief episodes of mating. Another focus of interest was the interplay between a genetic disposition for aggressive behavior and the early exposure experiences. The subjects used in the study were male mice of the fiftysixth generation of selection for high (Turku aggressive, TA) and low (Turku non-aggressive, TNA) levels of aggressiveness. Moderately aggressive males of the parental strain (normal, N) were also used. Subjects of each strain were exposed from 21 to 32 days of age to mating mice behind a wire mesh screen. Control subjects were placed in a comparable enclosure, but were exposed to nothing. The results showed that male mice exposed to mating early in life showed a higher rate of activities in the sexuality tests, including aggressive responses. A genetic potential for aggressive behavior was related to a higher degree of sexual activity, and the early exposures optimized the hereditary attributes. The relation between sexual and aggressive behavior is discussed. © 1994 Wiley-Liss, Inc.     

Differences between two strains of mice,selectively bred for high and low aggressiveness,in the capacity of male odors to affect aggressive behavior

The connection between a genetic disposition for aggressive behavior and the odor signal system in male mice was studied. The males belonged to two strains of mice which have been developed by selective breeding for high- (TA) and low aggressiveness (TNA). Urine from the high aggressive strain (TA), when applied to castrates, stimulated the aggressiveness of NMRI males while TA-soiled bedding suppressed their aggressiveness. In response to male odors from the low aggressive strain (TNA), the NMRI males showed quite contrasting reactions. The results provide evidences of a correlation between the hereditarily determined disposition for aggressive behavior and the odor signal system in TA- and TNA males.     

Gender-specific social experiences and the development of aggressive and sexual behavior in male mice

This study examined influences of gender-specific social experiences on the development of aggressive and sexual behavior in male mice. To determine the effects of gender-specific social experience three different types of groups were constituted after the animals had been weaned. The subjects were randomly assigned to different treatments. Female groups were composed of one experimental male and three female cohabitants. Male groups were composed of five experimental males each, and the mixed-sex groups were composed of two experimental males and of two females. The experimental subjects stayed in these groups until the age of approximately three months, when the testing for sexual and aggressive behavior commenced. For the sexuality tests, a receptive female was placed in the home cage of the experimental male for ten minutes. A nonaggressive male was placed in the home cage of the experimental male for seven minutes for the aggression tests. The experimental males were administered both sexuality and aggression tests, the sequence of testing sexual and aggressive behavior was systematically varied in order to control the influence of the two different types of behavioral tests. The results showed that males with only male social experiences showed fewer responses and were less active in both the aggression and sexuality tests than the males from the two other types of groups. Significant positive correlations between activity during aggression and sexual tests were obtained for all three groups. © 1994 Wiley-Liss, Inc.     

Effects of alpha and beta adrenergic antagonists on aggressive behavior in male mice

The effects of a variety of alpha and beta adrenergic antagonists were examined on the social encounters of isolated male mice with anosmic male partners. A range of alpha antagonists, including phentolamine, prazosin, and yohimbine, all suppressed social aggression. A range of beta antagonists, including propranolol, atenolol, metaprolol, and ICI 118, 551, also reduced this type of attack. Ethological assessment of the lowest effective dose of these adrenergic antagonists revealed a marked inhibitor action on offensive, social, and nonsocial behavior, while defensive responses and immobility were enhanced. It is concluded that the noradrenergic system has a significant non-specific role in mediating intermale aggression via both alpha and beta adrenergic receptor subtypes. © 1993 Wiley-Liss, Inc.     

Differential effect of handling on adult aggression in male mice bidirectionally selected for attack latency

Individual variation in intermale aggression is to a significant degree based upon genetic variation, but environmental factors can also exert their influence on the level of aggression. Moreover, genotype–environment interactions are a well‐known phenomenon. In the present experiment, I tested whether cage size or handling during development had an influence on adult attack latency scores. To be able to study a genotype–environment interaction, mice from two bidirectionally on attack latency selected lines were used. The size of the cage in which the mice grew up had no long‐term effect on aggression, neither in the high‐ nor in the low‐aggressive line. Handling, however, significantly increased the adult aggression of males from the low‐aggressive line. Despite the differential effect of handling on genetically high‐ and low‐aggressive mice, handling was not able to undo the marked differences in attack latencies between mice from both lines. Aggr. Behav. 25:365–368, 1999. © 1999 Wiley‐Liss, Inc.     

Effects of novel odors on intermale attack behavior in mice

Offensive, defensive, and nonagonistic social behaviors of resident male mice toward unfamiliar intruders were examined during exposure to the novel odors of chocolate or sheep's wool. Both novel odors reduced lateral attacks and boxing when compared to familiar sawdust odor. Chocolate, but not sheep's wool, also reliably increased flight behavior by residents. Neither social behaviors nor self-grooming were affected by these odors. The novel odors had no effect upon, or actually decreased, the defensive responses of intruders towards residents. The equivalent effectiveness of both predator and nonpredator odors in elevating risk assessment and suppressing attack during firsttime exposure, and the decreased potency of cat odors following repeated exposure, suggests that novelty contributes to the enhanced defensiveness seen among subjects during initial exposure to predator odors. © 1995 Wiley-Liss, Inc.     

Stages in the development of aggressive behavior in early childhood

Primary manifestations of aggression appear in the behavior of children in the second half of the first year of life. The frequency of Occurrence of interpeer aggression increases with age, and reaches its maximum in the third year. The frequency of aggression may later decrease, but there are considerable individual differences. Changes a h Occur in the form in which aggression is manifested; its motivational background and associated elicitors; its direction, duration, timing, and other operational characteristics, and in the modes of its acquisition. A certain continuity may be traced, however, in any of these features and the development of aggression may be perhaps more adequately represented by the following sequence of developmental stage:

• 1 Stage of preaggressive behavior;
• 2 Stage of primary differentiation;
• 3 Stage of the appearance of the individual pattern of aggressive behavior;
• 4 Stage of secondary differentiation of aggression;
• 5 Stage of the beginning of the transition into covert behavior—internalization of aggression

These stages represent certain facets of the interaction between the changing behavioral performance of the child and herlhis social environment, and may be used for evaluating aggressive behavior in young children.     

The relationship between aggressive and sexual behavior in male mice: Effects of testosterone and parachlorophenylalanine

The purpose of this study was to clarify the connection between aggressive and sexual behavior with the aid of testosterone propionate (TP) and parachlorophenylalanine (PCPA). Previous studies have indicated that aggressive and sexual behavior are positively correlated, and it has been suggested that both behaviors are related to the level of general arousal. Testosterone has documented effects on both aggressive and sexual behavior. It has been hypothesized that these effects are due to an increased level of general arousal. If this is the case, aggressive and sexual behavior could be restored by administration of drugs excitating the central nervous system, e.g., PCPA. The present study examined the effects of TP and PCPA on aggressive and sexual behavior in gonadectomized male mice. Control animals were injected with sesame seed oil or saline. The level of aggressiveness was assessed by means of dyadic tests with gonad-intact male opponents. For the sexuality tests, a receptive female was placed in the home cage of the experimental male. The results showed that male mice injected with PCPA were more aggressive than the males of the other groups, while the TP-exposed males expressed the most sexual activity. Compared to the control group, the PCPA and TP groups were more active in both the aggression and the sexuality tests. These findings lend support to the hypothesis that the earlier documented correlations between aggressive and sexual behavior could be due to both behaviors being dependent on a certain level of general activation. Aggr. Behav. 24:367–377, 1998. © 1998 Wiley-Liss, Inc.     

Strain‐specific aggressive behavior of male mice submitted to different husbandry procedures

Severe aggression within groups of male laboratory mice can cause serious welfare problems. Previous experiments have shown that the transfer of specific olfactory cues during cage cleaning and the provision of nesting material decrease aggression and stress in group‐housed male mice. In this study, the combined effect of these husbandry procedures was tested for their long‐term effect on aggression in two strains of male mice (BALB/c and CD‐1). We used postcleaning aggressive behavior, wound counts, and testosterone levels as indicators of aggressiveness. Physiological responses to social challenge were investigated through urinary corticosterone and adrenal tyrosine‐hydroxylase measurements. Furthermore, the aggression‐modulating effects of two enrichment items (ShepherdShack/DesRes and PVC tube) were explored. Marked differences were found between the two strains. CD‐1 mice were more aggressive, had higher testosterone levels but lower corticosterone levels, and had fewer wounds than BALB/c mice. However, in neither of the two strains was long‐term enrichment with nesting material and its transfer after cage cleaning effective in lasting reduction of intermale aggression. This may be explained by the fact that aggression levels were generally low. It seems that housing mice in small, socially stable groups or keeping social disturbances to a minimum considerably modulates aggression in group‐housed male mice. Mice of both strains housed in cages enriched with nesting material had lower urinary corticosterone levels than standard‐housed mice. We therefore conclude that the long‐term provision of nesting material, including the transfer of nesting material during cage cleaning, may enhance the welfare of laboratory mice. Aggr. Behav. 29:69–80, 2003. © 2002 Wiley‐Liss, Inc.     

Studies on wild house mice VI: Differential effects of the Y chromosome on intermale aggression

The aim of this study is to determine the effects of different parts of the Y chromosome of wild house mice on aggression. To reach this goal, intercrosses were made between two selection lines for attack latency (SAL and LAL) and their congenic strains (SAL. LY and LAL. SY). This procedure resulted in F₁ hybrids that carried the same autosomes, but differed in their X chromosome and the two different parts of their Y chromosomes, the different parts of the Y chromosome being a recombining part called the pseudoautosomal region (PAR) and a non-recombining part (non-PAR). We conclude that both parts of the Y chromosome contribute slightly but significantly to variation in aggression. The major effect is accomplished by the PAR of the aggressive parent; a mirror effect is achieved by the non-PAR of the aggressive parent in interaction with the PAR. © 1994 Wiley-Liss, Inc.     

Effects of selective breeding for high and low aggressiveness and of fighting experience on odor discrimination in mice

The present study was designed to determine whether male and female mice, selectively bred for high (TA) and low (TNA) aggressiveness, react in different ways when exposed to odors from males of the same strains. The effects of losing or winning fights on odor preferences in the TA males were also studied. The low aggressive TNA males were found to avoid areas soiled by the highly aggressive TA males. The TA males, on the other hand, were most interested in the areas soiled by other highly aggressive TA males. Along with decreasing aggressiveness, losing fights radically changed the odor preferences of the TA males, the soiled bedding from winner TA males now having a strong aversive effect. TNA females preferred the odors of TA males, while the TA females preferred the odors of TNA males. The genotype of the receiver of odor cues is important for the preference choices; this effect can, however, be changed through experience.     

Evaluating the effect of educational media exposure on aggression in early childhood

Preschool-aged children (M = 42.44 months-old, SD = 8.02) participated in a short-term longitudinal study investigating the effect of educational media exposure on social development (i.e., aggression and prosocial behavior) using multiple informants and methods. As predicted, educational media exposure significantly predicted increases in both observed and teacher reported relational aggression across time. Follow-up analyses showed that educational media exposure also significantly predicted increases in parent reported relational aggression across more than a two year period. Results replicate and extend prior research that has demonstrated links between educational media exposure and relational aggression, but not physical aggression, during early childhood.     

Effects of prenatal cocaine and genotype on intermale agonistic behavior in Mus musculus

We exposed the pups of three F₁ genotypes of mice to a daily regime of cocaine by injecting their mothers (all C57BL/10J strain) on days 7–18 of gestation with 20 mg/kg subcutaneously. Pups of the cocaine and control groups did not differ on measures of maternal and pup health or size. Male pups were weaned and isolated at 21 days of age and their behaviors measured in an intermale aggression situation at about 80 days of age. Treated and untreated males of each F₁ genotype were paired in dyads with either a C3H/HeJ (hawk-like) or AKR/J (retaliator-like) standard tester male. Standard tester males were not exposed to cocaine. Cocaine treatment alone reduced the overall level of aggression in dyads, and in interaction with genotype or the standard tester it altered the behavior of dyads in all phases of social interaction: the initiation, content, and outcome. Standard testers used as behavioral probes, differentiated cocaine and control males with respect to their stimulus and behavioral qualities. Aggr. Behav. 23:183–196, 1997.© 1997 Wiley-Liss, Inc.     

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.     

Effects of neonatal cyproterone acetate administration on isolation-induced fighting behavior and mounting behavior in male and female TO strain albino mice

The effects of a single dose (1 mg) of cyproterone acetate administered on either day 1 or day 20 of life on the adult behaviors of male and female TO strain albino mice were studied. The mice were tested both in a “standard opponent”-type situation and in a similar test using a hormonally primed receptive female, after being gonadectomized and maintained with testosterone propionate as adults. Neonatal treatment with this compound had little effect on subsequent fighting behavior in either sex, but clear evidence was produced that this treatment masculinized the sexual behavioral potentialities of the females, an effect which was apparent in animals which had been injected on either day 1 or day 20 of life. Indications were obtained that females treated neonatally with cyproterone acetate were capable of differentiating between the male and female “opponents” in a manner similar to the male. The effects of this treatment on fighting behavior consequently appear to be dissimilar to the effects of neonatal castration in this species. However, the effects on mounting behavior in the females, evidenced in adulthood, seem Likely to be a consequence of the weak androgenic properties of the antiandrogen. The administration of cyproterone acetate neonatally appears to have a more dramatic effect on the adult weights of endocrine organs in females than in mates.     

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.     

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.     

A sensory contact model for the study of aggressive and submissive behavior in male mice

The technique for simultaneous development of aggressive and submissive behaviors as a result of successive experiences of defeats or victories in daily intermale confrontations in male mice permanently living under sensory contact conditions is offered for behavioral, pharmacological, and neurophysiological studies of mechanisms of agonistic social relations. Distant sensory contact is achieved by placing a pair of males into a common cage separated by a transparent partition with holes permitting visual contact and the individuals perceiving each other's odors but preventing any physical at contact all times except for 10-min daily tests. These conditions essentially elicit aggression in winner males and quickly result in submission by losers of the same strain of mice. The meaning of consecutive stages of the technique, the problem of controls, and applications of this model are discussed.     

Effects of NMDA receptor channel blockade on aggression in isolated male mice

N‐Methyl‐D ‐aspartate (NMDA) receptor antagonists are perspective candidates for medication development for a number of diseases/states that are associated with increased aggressiveness (e.g., opioid withdrawal). The prototypic NMDA receptor antagonist phencyclidine (PCP) itself is a widely abused substance and is known to elevate levels of aggression in drug users. The present study was aimed at testing several drugs that share with PCP the ability to block NMDA receptor–associated channel. The resident‐intruder procedure was used to assess drug effects on aggressive behavior in isolated male mice. Resident aggressive mice were administered NMDA channel blockers (PCP; 0.3–10 mg/kg), dizocilpine (MK‐801; 0.01–0.3 mg/kg), memantine (1–30 mg/kg), and MRZ 2/579 (0.1–5.6 mg/kg). The competitive NMDA receptor antagonist D CPPene (0.1–5.6 mg/kg) was also tested as a compound representing an alternative approach to reduce activity of NMDA receptor complex. PCP, dizocilpine, and memantine inhibited expression of aggressive behaviors only at doses that produced ataxia. The novel channel blocker MRZ 2/579 also produced ataxia at the highest dose level but failed to affect aggressiveness. Reduction in aggression with a corresponding increase in sociability was observed after administration of D ‐CPPene. Overall, the present results suggest that NMDA receptor channel blockers do not exert selective effects on aggressive behavior. Aggr. Behav. 25:381–396, 1999. © 1999 Wiley‐Liss, Inc.