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PubMed1993

Persistent effects on maternal aggression of pregnancy but not of estrogen/progesterone treatment of nonpregnant ovariectomized rats revealed when initiation of maternal behavior is delayed.

Two experiments explored the effects on subsequent maternal aggression of interspersing 5-24 days between pregnancy termination and pup exposure to elicit maternal behavior. Pregnancy-terminated females displaying maternal behavior were compared to nonpregnant females also stimulated by pups to behave maternally and to pregnancy-terminated groups that were not exposed to pups. Pregnancies were terminated by hysterectomy-ovariectomy on Gestation Day 19 (G19), with pup exposure commencing after 6 days (Expt. 1), and by Cesarean section + ovariectomy (OVX), after delays of 5, 10, or 24 days (Expt. 2). In each study pregnancy-terminated, maternal groups were more aggressive than both nonpregnant, maternal groups and pregnancy-terminated, nonmaternal groups regardless of the imposed delays. In Expt. 2, postsurgical interval also was a significant factor, suggesting that surgical stress may elevate maternal aggression for several days. Prolonged treatment of nonpregnant OVX females (Expt. 3) with estrogen and progesterone elevated maternal aggression when pup exposure commenced 2 but not 7 days after termination of hormone treatment (Expt. 3). Therefore the physiological changes initiated during pregnancy that support maternal aggression persist for at least 4 weeks and may involve factors in addition to ovarian hormones that stimulate maternal behavior and maternal aggression. An additional unexpected finding was that nonpregnant (OVX) females had significantly higher Aggression scores after initiating maternal behavior.

Aggression↗
PubMed1995

Maternal aggression in rats: effects of olfactory bulbectomy, ZnSO4-induced anosmia, and vomeronasal organ removal.

Previous studies from our laboratory indicate that somatosensory inputs to the snout and ventral trunk, but not visual or auditory stimuli, play critical roles in the elicitation and maintenance of maternal aggression by lactating Norway rats toward a strange male intruder. There are conflicting reports on the influence of olfaction on maternal aggression. We explored the possible roles of central or peripheral anosmia on maternal aggression in Long-Evans rats during early lactation. In Experiment 1, responsiveness to both volatile and non-volatile odors was eliminated by bilateral olfactory bulbectomy (BOB), carried out during mid-gestation. BOB resulted in a reduced likelihood and intensity of maternal aggression on days 1 and 5 of lactation (L1 and L5), but also severe deficiencies in maternal behavior and litter growth and survival. In Experiment 2, anosmia to volatile odors was induced by spraying zinc sulfate intranasally on gestation day 21 and L1. This treatment had little or no effect on maternal aggression on L1 or L2 or on maternal behavior, especially if there was a 1-day recovery between the second treatment and testing. In Experiment 3, responsiveness to non-volatile odors was eliminated by vomeronasal-organ removal (VNX) carried out prior to mating. VNX did not disturb maternal behavior on L2-L8 or maternal aggression on L1 or L5. These results and others suggest that the expression of maternal aggression is affected by volatile odors, mediated possibly by accessory chemosensory systems such as the septal organ, or by neural changes that follow olfactory deafferentation, or both.

Aggression↗
PubMed2000

Mating season aggression and fecal testosterone levels in male ring-tailed lemurs (Lemur catta).

The challenge hypothesis (J. C. Wingfield, R. E. Hegner, B. G. Ball, and A. M. Duffy, 1990, Am. Nat. 136, 829-846) proposes that in birds, reptiles, and fish, "the frequency or intensity of reproductive aggression as an effect of T[estosterone] is strongest in situations of social instability, such as during the formation of dominance relationships, the establishment of territorial boundaries, or challenges by a conspecific male for a territory or access to mates" (p. 833). To determine the extension of this hypothesis to mammalian species, we tested predictions of the hypothesis in a nonpaternal, seasonal breeding, prosimian primate (ring-tailed lemurs, Lemur catta). Semi-free-ranging males were studied during periods of social stability (premating period) and instability (mating period). The annual mating season consists of several days during which males fight for access to promiscuous group females as each individually becomes sexually receptive for 1 day. Male rates of aggression were compared to fecal testosterone levels within premating and mating periods. In the premating period male rate of aggression was not significantly correlated with testosterone level. By contrast, during the mating season testosterone and aggression levels were positively and significantly correlated. However, on days just preceding estrus, male rate of aggression was not significantly correlated with testosterone, but on days of estrus, when aggressive challenges peaked sharply, testosterone and aggression were highly positively correlated. These results suggest that the challenge hypothesis applies to mammals as well as to birds, reptiles, and fish. In addition, elevations in testosterone were tightly circumscribed around days of estrus, suggesting a compromise between costs and benefits of elevated testosterone levels.

Aggression↗
PubMed2001

Testosterone, paternal behavior, and aggression in the monogamous California mouse (Peromyscus californicus).

Testosterone (T) mediates a trade-off, or negative correlation, between paternal behavior and aggression in several seasonally breeding avian species. However, the presence or absence of a T-mediated trade-off in mammals has received less attention. We examined the relationship between paternal behavior and territorial aggression in the biparental California mouse, Peromyscus californicus. In contrast to seasonally breeding birds, T maintains paternal behavior in this year-round territorial species. Castration reduced paternal behavior, whereas T replacement maintained high levels of paternal behavior. We hypothesize that T is aromatized in the brain to estradiol, which in turn stimulates paternal behavior. In contrast to paternal behavior, aggressive behavior was not reduced by castration. Interestingly, only sham males showed an increase in aggression across three aggression tests, while no change was detected in castrated or T-replacement males. Overall, trade-offs between aggression and paternal behavior do not appear to occur in this species. Measures of paternal behavior and aggression in a correlational experiment were actually positively correlated. Our data suggest that it may be worth reexamining the role that T plays in regulating mammalian paternal behavior.

Aggression↗
PubMed2001

Vasopressin and aggression in cross-fostered California mice (Peromyscus californicus) and white-footed mice (Peromyscus leucopus).

To examine how developmental experiences alter neural pathways associated with adult social behavior, we cross-fostered pups between the more aggressive and monogamous California mouse (Peromyscus californicus) and the less aggressive and polygamous white-footed mouse (P. leucopus). Cross-fostered males became more like their foster parents when tested as adults. Male white-footed mice became more aggressive only in an aggression test in a neutral arena, whereas the territorial California mice became less aggressive in resident-intruder aggression test, as measured by attack latency. Only the species that displayed a change in resident-intruder aggression showed a change in arginine vasopressin (AVP) levels: cross-fostered California mice had significantly lower levels of AVP-immunoreactive (AVP-ir) staining than controls in the bed nucleus of the stria terminalis (BNST) and the supraoptic nucleus (SON) and a nonsignificant trend toward lower levels in the medial amygdala (MA). Neither species showed changes in AVP-ir staining in a control area, the paraventricular nucleus (PVN). The changes in AVP-ir staining in the BNST and SON may not be caused by stress because cross-fostering was not associated with changes in adult plasma concentrations of two steroid hormones, corticosterone and testosterone, that have been associated with stress-related alterations in AVP pathways. These results suggest that manipulating the early parental environment can directly alter both a neurotransmitter system and species-typical patterns of social behavior, but that these effects may vary between species and under different social contexts.

Aggression↗
PubMed2002

Seasonal differences in the hormonal control of territorial aggression in free-living European stonechats.

In birds, territorial aggression during the breeding season is regulated by testosterone (T). However, many bird species also express aggressive behavior during the nonbreeding season, when plasma levels of T are low. It has been suggested that during this period estrogens might play a major role in regulating territorial aggression. In the present study we compared the effects of simultaneous blockage of androgenic and estrogenic actions on territorial aggression during the breeding and nonbreeding seasons in free-living male European stonechats (Saxicola torquata rubicola). European stonechats are of particular interest since they establish territories and form pairs during both the breeding and the nonbreeding seasons. Thus territorial aggression and its endocrine control can be compared between reproductive and non-reproductive contexts. Inhibition of androgenic and estrogenic actions by simultaneous application of Flutamide and ATD reduced territorial aggression during the breeding season, but not during the nonbreeding season. Our results show that androgens and/or estrogens are involved in the endocrine control of territorial aggression in stonechats only in a reproductive context, but not in a non-reproductive one.

Aggression↗
PubMed2002

Repeated anabolic-androgenic steroid treatment during adolescence increases vasopressin V(1A) receptor binding in Syrian hamsters: correlation with offensive aggression.

Repeated anabolic-androgenic steroid treatment during adolescence increases hypothalamic vasopressin and facilitates offensive aggression in male Syrian hamsters (Mesocricetus auratus). The current study investigated whether anabolic-androgenic steroid exposure during this developmental period influenced vasopressin V(1A) receptor binding activity in the hypothalamus and several other brain areas implicated in aggressive behavior in hamsters. To test this, adolescent male hamsters were administered anabolic steroids or sesame oil throughout adolescence, tested for offensive aggression, and examined for differences in vasopressin V(1A) receptor binding using in situ autoradiography. When compared with control animals, aggressive, adolescent anabolic steroid-treated hamsters showed significant increases (20-200%) in the intensity of vasopressin V(1A) receptor labeling in several aggression areas, including the ventrolateral hypothalamus, bed nucleus of the stria terminalis, and lateral septum. However, no significant differences in vasopressin V(1A) receptor labeling were found in other brain regions implicated in aggressive responding, most notably the lateral zone from the medial preoptic area to anterior hypothalamus and the corticomedial amygdala. These data suggest that adolescent anabolic steroid exposure may facilitate offensive aggression by increasing vasopressin V(1A) receptor binding in several key areas of the hamster brain.

Aggression↗
PubMed1997

Longitudinal perspective on alcohol use and aggression during adolescence.

While there is general agreement that alcohol use and aggression are related, few studies have examined this relationship among youth. This chapter reviews the literature on rates of alcohol use, aggression, and alcohol-related aggression among adolescents, as well as the cross-sectional and longitudinal associations among these behaviors. In general, the literature does not provide strong support for a unique association between alcohol use and aggressive behavior during adolescence. The observed relationship between alcohol use and aggression appears to be spurious because both behaviors are predicted by a similar set of individual, family, and environmental factors. Prevention programs that reduce these common risk factors should decrease both behaviors. Interventions with aggressive individuals, especially aggressive individuals who drink heavily, may be most indicated.

Adolescent↗
PubMed1983

Patterns of aggression in the personality structure of depressed patients.

The personality characteristics of 208 depressed patients of both sexes were studied by means of a Swedish personality inventory--the KSP--when the patients had recovered from the depressive syndrome. The patients in the study were divided into unipolars, bipolars, neurotic-reactive and "unspecified", i.e. those patients who did not meet the criteria for inclusion in any of the aforementioned groups. Female patients scored higher on variables of anxiety and psychasthenia and male patients scored higher on variables indicating distance preference and hostility. Several traits, in particular those reflecting aggression-out and hostility-out, appeared to be negatively correlated with age, whereas inhibition of aggression appeared to be positively related with age. Bipolar patients scored slightly differently from unipolars in many variables but none of the differences was significant. Neurotic-reactive patients distinguished themselves from the other in variables of aggression-out. Several interrelations between different personality characteristics and aspects of aggression have been investigated. Significant correlation could be shown between aspects of aggression and socialization, impulsiveness and aspects of anxiety. A positive correlation was shown between inhibition of aggression and social desirability, and both variables were shown to correlate with age. It is concluded that the difference in inhibition of aggression between "endogenous" and "non-endogenous" patients found in earlier studies might be due to a difference in age, and to the influence of social desirability.

Adult↗
PubMed1985

Testosterone modulates the effects of ethanol on male mouse aggression.

In a series of three experiments, we evaluated the degree to which the effects of acutely administered ethanol on aggressive behavior of male CFW mice toward a male intruder interact with, and depend on, androgen levels. In the first experiment, mice were tested at 15 min after 0, 0.1, 0.3, 1.0, 1.7, or 3.0 g/kg of ethanol PO. The highest dose (3.0 g/kg) significantly suppressed aggression by the male residents. In the second experiment, aggressive behavior was suppressed from 5 to 60 min after 3.0 g/kg ethanol administration PO. The third experiment evaluated the role of testosterone in these effects in another set of male mice that were castrated and then implanted with a 7.5-mm or 2.5-mm silastic capsule of testosterone (T) or a silastic capsule containing cholesterol as a control. The castrated mice with 2.5-mm T capsules or cholesterol capsules had lower baseline levels of aggression than intact mice or castrated males with 7.5-mm T capsules, but they demonstrated an alcohol dose-response pattern similar to that of the intact males. The castrated males with 7.5-mm T capsules had a different dose-response curve than the other males. Doses of 1.0 and 1.7 g/kg ethanol PO significantly enhanced aggression; 5.6 g/kg was required to suppress aggression. Ethanol effects on aggressive behavior did not require T or changes in T level, but T levels altered behavioral sensitivity to ethanol.

Aggression↗
PubMed1982

Evidence for central histaminergic mechanism in foot shock aggression.

The role of central histaminergic system in foot shock induced aggression was studied in mice. Histamine administered by intracerebral (IC) injection (25-200 micrograms) produced a significant increase in fighting episodes in a dose dependent manner. It was observed that mepyramine (H1 blocker) given intraperitoneally (IP) significantly increased and metiamide (H2 blocker) given IC decreased significantly the fighting response. To determine the nature of receptors involved in histamine induced facilitation of aggressive behaviour, histamine was administered IC in mice pretreated with mepyramine or metiamide. Mepyramine pretreatment further increased the facilitatory effect of histamine while metiamide blocked the enhancement of aggressiveness by histamine. Combined pretreatment with metiamide and mepyramine decreased significantly the fighting counts which remained unaffected after histamine. Haloperidol did not block the enhancement of aggression by histamine or mepyramine. However, atropine pretreatment partially inhibited the histamine induced increase in the fighting counts. Results of pretreatment with metiamide and atropine were similar to those obtained with pretreatment of metiamide and mepyramine. Metiamide alone or in combination with atropine failed to affect the facilitatory effect of amphetamine on the foot-shock aggression. It is concluded that central histamine H2 receptors have a facilitatory role and H1 receptors an inhibitory role on aggressive behaviour in mice induced by foot-shock. Since histamine per se had a facilitatory effect on foot-shock induced aggression, the central H2 receptors seem to dominate over the H1 receptors.

Aggression↗
PubMed1981

Effects of smoking different doses of nicotine on human aggressive behavior.

A new methodology was employed to study the effects of drugs on human aggressive behavior in a laboratory situation. The effects of not smoking, smoking a low nicotine dose (0.42 mg/cigarette), and smoking a high nicotine dose (2.19 mg/cigarette) on human nonaggressive and aggressive responding was determined. A nonaggressive response, which resulted in the accumulation of money, was continuously available to the subject. Two different aggressive responses were also available: the ostensible subtraction of money from, and the ostensible presentation of a 1-s blast of white noise to a (fictitious) person. Aggressive responding was elicited by subtracting money from the research subjects, which was attributed to a fictitious person paired with the research subject randomly each day. Nicotine, administered with experimental cigarettes, produced dose-dependent decrease in both types of aggressive responding elicited by low or high frequency subtractions of money attributed to another person. Generally, the more aggressive response option, i.e., subtraction of money from another person, decreased more following nicotine administration. Smoking the same doses of nicotine increased nonaggressive monetary reinforced responding. This indicates that the suppressant effects of nicotine on aggressive responding was not due to a non-specific depressant action.

Aggression↗
PubMed1984

A 3-year follow-up of aggressive and withdrawn behavior in childhood: preliminary findings.

The school placement of 122 aggressive, 150 withdrawn, 182 aggressive-withdrawn, and 299 control children was determined 3 years following their original selection. Children identified by peers as aggressive-withdrawn or aggressive were more likely to have failed a grade or to be in a special class than were withdrawn children or controls. Older aggressive-withdrawn subjects and controls, but not aggressive subjects or withdrawn subjects, had higher rates of school failure and special class placement. Fewer boys than girls were in a regular class at the expected grade level. The results underline the importance of childhood aggression as a predictor of later academic adjustment. Implications of these findings for the interpretation of measures of behavioral stability are discussed.

Achievement↗
PubMed1989

A comparison of aggressive and withdrawn children's self-esteem, optimism and pessimism, and causal attributions for success and failure.

Aggressive children, withdrawn children, combined aggressive and withdrawn children, and children displaying neither aggressive nor withdrawn behavior were compared on three self-appraisal measures: (a) self-esteem, (b) attributions to ability and lack of ability following success and failure, and (c) optimism and pessimism about one's long-term personal future. From an initial sample of 583 elementary school children, independent and extreme groups were identified by combined ratings of teachers and classmates. Solely aggressive children had higher self-esteem than either solely withdrawn children or children who were both aggressive and withdrawn. The control group of children who were neither aggressive nor withdrawn had the highest self-esteem of all. The control group also attributed success to ability more than the two groups of children with high withdrawal scores but did not differ from the solely aggressive children. There were no significant differences among the groups in attributions to lack of ability following failure or in optimism or pessimism.

Achievement↗
PubMed1989

Relations between hyperactive and aggressive behavior and peer relations at three elementary grade levels.

Sociometrics and teacher ratings of hyperactivity and aggression were obtained on 390 boys in grades 1-6 to explore the relative contributions of hyperactivity and aggression to children's social adjustment. Both hyperactivity and aggression were correlated with negative sociometric nominations at all grade levels; however, only hyperactivity showed consistent inverse correlations with positive sociometric nominations. In multiple regression analyses, hyperactivity contributed incremental variance to the prediction of problematic sociometric status at all grade levels, while aggression did so only at grades 3-4. An examination of the core symptoms of hyperactivity revealed that motor hyperactivity, in the absence of impulsivity and inattention, did not predict negative sociometric status at any grade level. Subgroups of boys categorized as hyperactive only, aggressive only, hyperactive/aggressive, and nonhyperactive/nonaggressive controls were compared on teacher ratings and sociometrics. Hyperactive/aggressive boys had higher hyperactivity and aggression ratings than boys in either of the single-problem groups; all three behavior problem groups had more negative social status than controls. Developmental changes in children's normative expectations for social behavior were discussed as possible mechanisms mediating the age-related differences in relations among aggression, hyperactivity, and peer relations.

Adolescent↗
PubMed1996

A revised teacher rating scale for reactive and proactive aggression.

A teacher rating scale of reactive aggression, proactive aggression, and covert antisocial behavior was evaluated in a normative sample of third- to fifth-grade predominantly white lower middle class boys (N = 186). Factor analysis revealed independent and internally consistent Reactive Aggression (six reactive items), and Proactive Aggression (five proactive items, five covert items) factors. Although the factors were intercorrelated (r = .67), and each factor was significantly correlated with negative peer social status (r = .26 for each, controlling for grade), the independence of the factors was supported by the unique relation of Reactive Aggression with in-school detentions (r = .31), controlling for Proactive Aggression and grade. These results supported the reliability and validity of Reactive and Proactive Aggression as rated by teachers, which should facilitate further research of these constructs.

Aggression↗
PubMed1996

Short-term stability of aggression, peer rejection, and depressive symptoms in middle childhood.

This study investigated the short-term stability of teacher-rated aggression, peer-rated rejection, and peer-rated depressive symptoms in 478 elementary school children from 25 classrooms (first to third grades) in two geographical areas. Children who presented specific combinations of aggression, rejection, and depressive symptoms were tracked to determine the stability of these combinations from the beginning (Time 1) to the end (Time 2) of the school year. In addition, aggression, rejection, and depressive symptoms were treated as risk factors, and children were classified as displaying zero, one, two, or three risk factors at Times 1 and 2. Of the three risk factors, aggression appeared to be the most stable. Three-quarters of children who presented aggression at Time 1 (either alone or in combination with the other risk factors) were found to continue to have elevated levels of aggression at Time 2. Although specific combinations of aggression, rejection, and depressive symptoms were not very stable over time, the number of risk factors a child displayed at Time 1 was a good predictor of the number of risk factors the child displayed at Time 2. Stability of risk factors was comparable as a junction of child gender and ethnicity.

Aggression↗
PubMed1991

Heritable variation for aggression as a reflection of individual coping strategies.

Evidence is presented in rodents, that individual differences in aggression reflect heritable, fundamentally different, but equally valuable alternative strategies to cope with environmental demands. Generally, aggressive individuals show an active response to aversive situations. In a social setting, they react with flight or escape when defeated; in non-social situations, they react with active avoidance of controllable shocks and with sustained activity during an uncontrollable task. In contrast, non-aggressive individuals generally adopt a passive strategy. In social and non-social aversive situations, they react with immobility and withdrawal. A main aspect of these two alternative strategies is that individuals with an active strategy easily develop routines (intrinsically determined behaviour), and consequently do not react (properly) to 'minor' changes in their environment, whereas in passively reacting animals it is just the other way around (extrinsically determined behaviour). It has become clear that active and passive behavioural strategies represent two different, but equivalent, coping styles. The coping style of the aggressive males is aimed at the removal of themselves from the source of stress or at removal of the stress source itself (i.e. active manipulation). Non-aggressive individuals seem to aim at the reduction of the emotional impact of the stress (i.e. passive confrontation). The success of both coping styles depends upon the variability or stability of the environment. The fact that aggressive males develop routines may contribute to a fast execution of their anticipatory responses, which is necessary for an effective manipulation of events. However, this is only of advantage in predictable (stable) situations, but is maladaptive (e.g. expressed by the development of stress pathologies) when the animal is confronted with the unexpected (variable situations). The flexible behaviour of non-aggressive individuals, depending strongly upon external stimuli, will be of advantage under changing conditions. Studies on wild house mice living under natural conditions show how active and passive coping functions in nature, and how the two types have been brought about by natural selection.

Adaptation, Psychological↗