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PubMed1987

Hormonal factors influence the onset of maternal aggression in laboratory rats.

This experiment addressed the hypothesis that aggressiveness toward conspecifics is stimulated by hormonal factors known to mediate the onset of maternal care. Subjects included both pregnant and virgin females. Sixteen-day pregnant rats were hysterectomized (H), hysterectomized-ovariectomized and injected with estrogen (HO-EB), or subjected to sham procedures. Nonpregnant females were HO-EB or sham operated. The females were sensitized by continuous exposure to pups and were judged to have initiated maternal care when all pups were retrieved and grouped, Aggressiveness was observed during 5-min intruder tests using unfamiliar males, administered (a) 10 min prior to the introduction of test pups, (b) following the first 3 hr of pup exposure, and (c) after females had initiated maternal care. The results revealed that treatments known to reduce sensitization latencies also increased aggressiveness even prior to exposure to pups. Aggressiveness was displayed before sensitization only in groups having elevated estrogen levels. After initiating maternal behavior, pregnant and pregnancy-terminated females increased further in aggressiveness whereas nonpregnant females did not. Pregnancy-terminated, HO-Oil females became aggressive (only) after initiating maternal behavior, indicating that factors other than estrogen also influence the onset of maternal aggression.

Aggression↗
PubMed1984

Aggression and allergic disorder in depressives.

This paper investigates the correlation between aggression and allergic disorder in various forms of depression. As a control factor to allergic disorder we used the factor infectious disease. The aggression was measured with 2 scales of the FAF (Fragebogen zur Erfassung von Aggressivitätsfaktoren--the Questionnaire for Measuring Factors of Aggression). The sample consists of 115 depressives, of whom 26 suffer from allergic disorders and 79 have a previous history of infectious diseases. We recorded significantly higher aggression scores for allergic subjects as opposed to non-allergic subjects (p less than 0.05) in nearly all the subgroups. We also discovered a similar though not so marked tendency for people with infectious diseases. Higher aggression scores are therefore not only specific for depressives with allergic disorders. Sex, psychiatric differential diagnosis and the form of the aggression are important for the degree of the aggression.

Aggression↗
PubMed1975

Technique for producing and measuring territorial aggression using laboratory mice.

A method was developed for producing and measuring territorial aggression in male CF-1 laboratory mice using a simple apparatus. The technique is based on data collected from approximately 1000 CF-1 mice in order to establish the parameters and optimize the procedures. In this technique the mouse takes up lone residence for 24 hr in a 60 cm square box attached by a tubular runway to a standard mouse (home) cage with food, water, and bedding. After this interval, a naive intruder male CF-1 mouse of the same age is introduced. Under control (no treatment) conditions, 85-90 percent of the resident mice will attack the intruder with a latency of about 5 min and all residents attacking the intruder are dominant. Dominance or submission is typically decided within the first 20 min of the test. Data on 10 pairs of mice can be collected simultaneously by one observer. Treatments can be assessed in terms of their effects on the production of aggression (percentage of animals attacking) in either the resident or the intruder, and on the level of aggression produced by recording the latency to attack, the frequency of attacks, and the number of animals wounded (showing blood) during the 20 min observation period. The advantages of the technique include the use of a naturally occurring aggressive behavior (as opposed to techniques empolying long periods of isolation, shock, or drugs), the highly reliable occurrence of aggression, the ability to study animals exposed to either aggression or defeat, the clear and valid measures of aggression produced, the simple and sturdy apparatus, and the convenience and economy of data collection.

Aggression↗
PubMed1977

Intra-uterine nutrition and its effects on aggression.

Prenatal zinc deficiency and prenatal undernutrition were found to have adverse effects on the food consumption and weight gain of pregnant dams and their offspring. Pups whose dams suffered prenatal zinc deficiency (ZD) consumed less food and gained less weight than pups whose dams suffered prenatal undernutrition (PF). The PF pups consumed less food and gained less weight than pups whose dams were normally fed (AL). The ZD females at age 75 days were significantly more aggressive than the PF females, while the PF females were more aggressive than the AL females. At age 105 days, ZD females were significantly more aggressive than the PF and AL females. There were no differences in aggression between the PF and AL females at 105 days. Among the ZD, PF, and AL male offspring, there were no differences in aggression at either age level except that the 75 day old PF males were significantly less aggressive than the AL males. Thus prenatal malnutrition, especially zinc deficiency, seems to have differential effects on the aggressive tendencies of female and male offspring.

Age Factors↗
PubMed1984

The effects of age and strain on aggression in male rats.

Aggressive behaviors were compared for male Fischer-344 and Long-Evans rats formed into mixed-sex colonies at 100, 200, or 300 days of age. Within each strain, male aggression did not differ across these ages, nor did it differ for an additional group of 600-day old Long-Evans males: both the form and the incidence of specific aggressive and defensive behaviors remained relatively constant over an age range representing nearly the entire normal life span for this species. However, Fischer-344 males at all ages were reliably lower in aggression than the Long-Evans rats. The specific aggression components seen in the Fischer-344 rats tended to be nondamaging, resembling "play fighting" more than the tissue damaging attack behaviors typical of other strains. Despite the frequent use of this strain in gerontological research, such low levels of aggressiveness counterindicate their use in research in aging and aggression.

Age Factors↗
PubMed1989

Vomeronasal organ removal and female mouse aggression: the role of experience.

Removal of the vomeronasal organ (VNX) from female mice had little effect upon fecundity, nest building and pup retrieval. Surprisingly, VNX significantly affected aggression by lactating females. Normally, lactating females will attack and fight intruders placed into the home cage, especially if the intruder is an unfamiliar male. In Experiment 1, we determined that VNX prior to sexual experience totally eliminated this type of aggression. Intact females were highly aggressive, but much more so to unfamiliar than to familiar males. Copulation prior to surgery did not ameliorate the effects of VNX; again, none of the VNX females were aggressive (Experiment 2). In Experiment 3, attacks and fights by previously aggressive primiparous females also were eliminated or significantly suppressed following VNX. Even when the testing occurred later during the postpartum period and for extended periods of time, this same suppression of aggression held following VNX. We conclude that aggression by lactating female mice is under strict mediation by chemosignals detected by the vomeronasal organ.

Aggression↗
PubMed1989

Competitive experience activates testosterone-dependent social aggression toward unfamiliar males.

Male hooded rats (350 to 450 g) were castrated and given subcutaneous implants of testosterone-filled or empty Silastic tubes. Four weeks later, half of the animals with testosterone implants were housed with an animal with an empty implant and left for 6 weeks. The other animals were adapted to a food-deprivation schedule, housed in testosterone-implant/sham-implant pairs and given a series of food-competition tests. Following the competition tests, all animals were observed individually in their living cage for aggression toward an unfamiliar intruder. Within the competitive situation, animals with testosterone implants were more aggressive and more successful at maintaining access to food than their cagemates with sham implants. In the unfamiliar intruder test, animals with testosterone implants that had been subjected to food competition were more aggressive toward an unfamiliar intruder than were animals with testosterone implants that had not been given competitive experience. Animals with testosterone implants given competitive experience were more aggressive than their castrated cagemates, but animals with testosterone implants not given competitive experience were not more aggressive than their cagemates. These results demonstrate that testosterone-dependent social aggression fostered by a competitive situation is elicited by an unfamiliar male intruder. They also confirm other evidence that activation of social aggression does not appear to require increased testicular testosterone secretion.

Aggression↗
PubMed1992

Interstrain aggression in hypertensive and/or hyperactive rats: SHR, WKY, WKHA, WKHT.

Four inbred rat strains, all derived from Wistar-Kyoto (WKY) rats, express hypertension and hyperactivity in all combinations: SHRs have both traits, WKYs have neither, WKHAs are hyperactive/normotensive, and WKHTs are hypertensive/normoactive. Rats of the four strains were tested for aggression, at one time only, by pairing subjects of same sex, same age, but different strain, in a novel arena, i.e., on neutral ground, for three consecutive, 5-min observation periods. Total aggression scores were highest in females, highest in the first 5-min period, and lower at 7-9 months than at younger ages. Allogrooming was more frequently observed than other types of aggression, such as attacks, mounts, aggressive postures, and blocks. Allogrooming scores were significantly elevated in the hypertensive strains, especially WKHT, and very low in the hyperactive strains, especially WKHA. The other forms of aggression were significantly higher in females with hyperactivity. It was concluded that interstrain aggression, as seen in SHRs and WKYs, is differentially expressed by two new strains genetically derived from them. Furthermore, no one strain among these four expresses all components of the behavioral responses seen in this form of aggression.

Aggression↗
PubMed1993

Intermale aggression in mice: does hour of castration after birth influence adult behavior?

In the mouse, perinatally present testicular androgens promote the development of the propensity for adult intermale aggression. In the newborn male mouse plasma testosterone more than doubles during the first 2 h after birth and then falls rapidly to remain relatively low for the remainder of the 24-h period after birth. To study whether this surge in plasma testosterone influences aggressiveness we castrated some male mice within 1 h after birth i.e., before the surge. We castrated other males between 1.5-6 h after birth, or 1, 6, or 12 days after birth. Males were given testosterone as adults and tested for aggression for 5 weeks. Males castrated within 1 h after birth were not clearly different from males castrated 1.5-6 h after birth with respect to aggressive behavior, although males in both groups were substantially less aggressive than males castrated later in life. Thus, the perinatal surge in plasma testosterone in the mouse does not appear to make a unique contribution to the organization of mechanisms for intermale aggression. Rather, this surge is probably the initial stimulus that begins the postnatal process by which testicular hormones promote the development of the potential for adult aggressive behavior. This process appears to be complete by 6 days after birth.

Aggression↗
PubMed1993

Genetic differences in female house mice in aggressive response to sex steroid hormone treatment.

Male mice, genetically selected for aggression, characterized by short attack latency (SAL) or long attack latency (LAL), differ on several testosterone (T)-related parameters during ontogeny and adult age. The variation in aggressive behavior at adult age may be due to differences in degree of androgenization prenatally. When exposed to T at prenatal, neonatal, and/or adult age, nonlactating females also display intraspecific fighting behavior. In the present study, we investigated in females of the SAL and LAL selection lines, whether the differentiation of aggression involves processes similar to ones seen in males. Therefore, we injected females with testosterone propionate (TP) or vehicle on the day of birth, treated them after ovariectomy at adult age with T, estradiol (E), or vehicle, and tested their aggressive response. We found that neonatally vehicle-treated SAL females show a higher aggressive response to chronic T treatment at adult age than LAL females receiving the same treatment. Females of both selection lines treated with vehicle or E as adults were not aggressive. Neonatal TP treatment did not influence the adult T sensitivity and difference between selection lines in response to T at adult age. However, neonatally TP-treated SAL females showed aggressive behavior when treated with E at adult age, whereas LAL females failed to do so. These results suggest a genetic difference in susceptibility to T and E, which plays a major role prenatally, in organizing the development of sex steroid-dependent neural systems.

Aggression↗
PubMed1995

Aggression is attenuated by ovariectomy in pregnant female rats given progesterone and estradiol replacement to maintain pregnancy.

Female rats were tested for aggression toward an unfamiliar female conspecific 13 days following the beginning of cohabitation with a male. Forty-eight hours later, half of the females that displayed aggression were ovariectomized. To maintain pregnancy, they were also given Silastic implants of estradiol (1-mm tube) and progesterone (6 tubes, 30-mm long; Dow-Corning tubing #602-305) sufficient to maintain pregnancy but at lower levels than those normally present. Control females were given a sham ovariectomy and implanted with empty tubes. Each animal received a second aggression test at 48 h following surgery and a third test, 3 days following the second. Hormone implants successfully maintained pregnancy and supported the normal development of the pups. However, Ovariectomized females with hormone implants did not spontaneously give birth. Ovariectomized females displayed less aggression than their sham-ovariectomized counterparts at the second and third aggression tests. The difference was due to an increasing level of aggression by the control but not the experimental animals. These results are consistent with other evidence that circulating gonadal hormones influence the onset of maternal aggression in the female rat.

Aggression↗
PubMed1979

Effects of lithium chloride injections on rank-related fighting, maternal aggression and locust-killing responses in naive and experienced 'TO' strain mice.

Three experiments investigated lithium chloride's (LiCl) effects on three forms of aggression in male 'TO' strain mice. Models of aggression investigated, included attack by preisolated males on male conspecifics (rank-related or intermale fighting), attack by lactating females on male intruders (maternal aggression) and the locust-killing response (a form of predatory aggression?) In the first study, injections of naive male mice with 0.2 and 0.4 mEq of LiCl resulted in marked declines in rank-related fighting. The effects of this treatment on locust killing could not be assessed, as this activity was already at a low incidennce in controls. In a second experiment, LiCl injection had little influence on the locust-killing response in selected, experienced male killer mice. As in Experiment 1, rank-related fighting was suppressed by this treatment. The third experiment revealed that LiCl injections did not influence either maternal aggression or locust killing in naive females and predatory aggression in experienced-killer females. These results provide further support for the contention that these three behaviors have very different physiological bases. The data suggests that one should be cautious when extrapolating between different models of aggression even within the same species.

Aggression↗
PubMed1987

Maternal aggression towards different sized male opponents: effect of chlordiazepoxide treatment of the mothers and d-amphetamine treatment of the intruders.

Lactating female rats vigorously attack equally sized conspecific males introduced into their home cage. Under conditions of such high aggression, the previously reported pro-aggressive action of a low (5 mg/kg) dosage of chlordiazepoxide (CDP) is hardly detectable. When opponents are large, the intensity of the aggression is less than what is seen with small ones. In this situation treatment of the females with CDP increases aggression levels substantially. The importance of intruders evoking aggression was further investigated by treating different sized opponents with d-amphetamine. d-Amphetamine treatment did not lead to major changes in the defensive capacities of either types of intruder. The data demonstrate that drug effects, such as pro-aggressive actions, may be observed using larger sized opponents that are not so easily defeated and show more adequate defense than small ones. The subtleness of the dyadic interactions in maternal aggression indicates that drug effects should be considered carefully before extrapolation to other conditions.

Aggression↗
PubMed1984

Depression, suicide, and aggression in alcoholics and their relationship to plasma amino acids.

In an earlier study we found an association in alcoholic patients between depression and low ratios of tryptophan over amino acids sharing with it the same transport carrier into the brain. A decreased tryptophan ratio has been shown to be correlated with lower brain tryptophan and serotonin. Because it has been postulated that altered serotonin metabolism may be a highly significant contributing factor not only to depression but also to aggressive and suicidal behavior, we decided to assess the existence of possible associations between amino acid abnormalities and these behaviors in a population of alcoholics. We observed a significant association between histories of aggression and depression. In addition, depressed patients with a history of aggression were found to have the lowest tryptophan ratio values. These values differed significantly from those found in depressed patients with no aggression history and from those observed in patients with no history of aggression and depression. Two of the three suicide attempters in the study fell also in the group of patients with an aggression history. Our data suggest the existence of a subgroup of alcoholics with marked amino acid abnormalities at risk for manifestations of depression, suicide, and aggression.

Adult↗
PubMed1984

A comparative study of aggression related changes in brain serotonin in CBA, C57BL, and DBA mice.

Spontaneous aggression was induced in 3 strains of male mice (CBA, C57BL, and DBA) by a new technique of socially intermixing them for 14 days and daily measuring the amount of scarring each received. In all strains, serotonin (5-HT) was lower in the ventromedial (VMH) and supraoptic (SO) hypothalamic areas and amygdala in the more aggressive as compared to the controls or less aggressive animals. The correlation coefficients between the amount of physical scarring and brain 5-HT in these areas ranged from 0.50 to 0.91 (P less than 0.05 to P less than 0.01). Hippocampal (HPC) 5-HT was also lower in the more aggressive animals in CBA mice. Also the most aggressive strain (CBA) tended to have the lowest SO, VMH, and amygdala 5-HT concentration. In all 3 strains the concentration of brain 5-HT from lowest to highest was: frontal cortex less than HPC less than amygdala less than VMH less than SO. The data suggest that there is an inverse relationship between hypothalamic and limbic 5-HT and aggressiveness. Also the data suggest that the technique of intermixing 3 strains of mice successfully induced spontaneous aggression which peaked around 14 days and was reliable and could be quantified.

Aggression↗
PubMed1993

Neuropsychological deficit and aggressive behavior: a prospective study.

1. Failures in higher cortical executive functions and dyscontrol of aggressive impulses were hypothesized to co-occur in aggressive men. 2. The performance of a sample of violent forensic patients on selected neuropsychological measures (Judgment of Line Orientation, Stroop Color Word Test, Emotion Perception Test, Test Of Nonverbal Intelligence, Wisconsin Card Sorting Test, and Symbol Digit Modalities Test) were used to predict their overt aggressive behavior during a one-year period using the Overt Aggression Scale. 3. Whole-set correlation analyses revealed that scores on the Judgment of Line Orientation, Stroop Color Word Test, and Emotion Perception Test accounted for 57% of the variance of aggression scores. 4. Frequency of aggression, but not severity of aggression, can be predicted using these three scores.

Adult↗
PubMed1993

Abnormal lateralization in finger tapping and overt aggressive behavior.

1. The relationship between abnormal cerebral lateralization and overt aggressive behavior was examined in 41 violent psychiatric patients in a maximum-security hospital. 2. Cerebral lateralization was measured using the Finger Oscillation Test from the Halstead-Reitan Neuropsychological Battery, and aggressive behavior was measured during a six-month period of hospitalization using the Overt Aggression Scale. 3. Patients with the most abnormal pattern of lateralization exhibited the highest frequency as well as the highest severity of overt aggressive behavior. This pattern could not be explained by the influence of age, race, IQ, history of head trauma, brain damage, or psychiatric diagnosis. History of seizures, alcohol abuse, and drug abuse, however, were found to be intervening variables in the lateralization-aggression link. Once their influence was removed using analysis of covariance, there was no relationship between lateralization and aggression. 4. The results suggest that it is unlikely that there is a direct causal relationship between abnormal lateralization and aggressive behavior.

Adult↗
PubMed1975

Catecholamine excretion, conscience function and aggressive behaviour.

This report deals with a study--carried out among 46 12-17-year-old-boys--of the relationship between: (1) the excretion of waste products of catecholamines (methyladrenaline and methylnoradrenaline) and creatinine, (2) aggressive behaviour in a laboratory setting, and (3) data obtained via a conscience-function questionnaire. The hypothesis that aggressive behaviour is positively correlated with methylnoradrenaline excretion was confirmed. As far as the conscience-function questionnaire was concerned, three dimensions could be distinguished. Methyladrenaline and methylnoradrenaline excretion proved to be reversely related to one of them, indicated as the 'intropunitiveness-aggressiveness dimension'. Intropunitive subjects appeared to have a higher methyladrenaline and a lower methylnoradrenaline excretion than aggressive subjects. The aforesaid dimension also correlated significantly with creatinine excretion, a finding which led to the interpretation that aggressive people possess greater muscular strength than more intropunitively inclined people. However, no significant correlations between aggression scores and questionnaire scores were found. The results are discussed against the background of arousal theories of aggressive behaviour.

Adolescent↗