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PubMed1999

Plasma L-tryptophan depletion and aggression.

There is a well-established relationship between aggression and lowered serotonin neuro-transmission. Recently developed methodologies for manipulating L-tryptophan levels (and brain serotonin) have been applied to human laboratory studies of aggression. Collectively, these studies provide further evidence for the serotonin-aggression relationship. Two important findings have been made recently: (1) subsets of individuals (e.g., persons self-rating high on aggressive or hostility scales) may differ in their susceptibility to aggression produced through plasma tryptophan depletion; and (2) alcohol in combination with L-tryptophan depletion has an additive effect on aggression. All previous studies have been conducted with men. Extending these studies to women appears to be the much-needed next step given that serotonergic levels appear to vary both as a function of the menstrual cycle phase and menstrual symptomatology.

Aggression↗
PubMed1976

[Aggressive behaviour induced by apomorphine: relations with some elements of the behavioural profile and with the sensitivity to apomorphine (author's transl)].

Aggressive rats could be differentiated from non-aggressive rats on a lower rate of rearing reactions in the open-field activity, as well as on a weaker aptitude for learning, increasing with the complication of the test. The two groups of rats had comparable activity, and a comparable response to pain. Apomorphine decreased the number of rearing reactions and defecations on open-field activity in the same manner in non-aggressive rats as in aggressive animals. In the usual housing conditions, apomorphine increased similarly locomotor activity in both groups, but in observation cages of "emotional" type, the increase was much more pronounced in aggressive rats than in non-aggressive animals.

Aggression↗
PubMed1985

Social status as determinant of alcohol effects on aggressive behavior in squirrel monkeys (Saimiri sciureus).

We investigated the behavioral effects of alcohol, especially those on aggression, on members of established groups of squirrel monkeys. A continuous measurement of monkey behavior in groups revealed consistent differences between dominant and subordinate animals. Dominant monkeys aggressed more frequently than subordinate monkeys, and spent less time in stationary postures. Alcohol produced dose-related biphasic changes in the number of threats, grasps, and displacements exhibited by dominant but not subordinate monkeys. Low doses of alcohol (0.1, 0.3, 0.6 g/kg) increased the frequency of aggressive behavior, and high doses (1.0 g/kg) decreased these behaviors. The largest change in behavior was evident in the first 20-40 min after injection, with a return to baseline 60-120 min later. The aggression-enhancing effect of alcohol in dominant monkeys required a stable baseline, which was obtained by daily administration of distilled water. Low levels of aggressive and associative behavior in subordinate monkeys were relatively unaffected at any dose of alcohol. They were associated with and aggressed against more often by untreated members of the group. The status-dependent effects of alcohol may be related to the neuroendocrine and neurotransmitter profiles characteristic of dominant and subordinate monkeys.

Aggression↗
PubMed1975

Inter-group aggression in mice: a new method for testing the effects of centrally active drugs.

A new method is described with which the effects of drugs on aggressive behaviour can be compared with their effects on general activity. Two groups of 3 male mice are housed in either half of a macrolon living cage which is divided down the middle by a non-transparent barrier. After 21 days the cage is placed on an activity meter and the dividing wall is removed. The ensuing fighting is scored by an observer and at the same time activity is measured using the activity meter. It was shown that aggression occurred mainly between groups with the dominant members doing most of the fighting. It appeared further that the two parameters measured--aggression and motor activity--respond differentially to the effects of standard psychotropic drugs. By this means it was possible to distinguish between the effects of chlorpromazine, pentobarbitone, chlordiazepoxide and d-amphetamine. In addition it was possible to confirm that an experimental compound, YG 19-256, which in other tests has been shown to inhibit aggressive behaviour without causing general sedation, also has selective anti-aggressive effects in this test. From these results it seems that the intergroup aggression test could well be useful in identifying different classes of psychotropic agents.

Aggression↗
PubMed1985

Interaction of dietary tryptophan and social isolation on territorial aggression, motor activity, and neurochemistry in mice.

This study examined the interaction of dietary tryptophan (TRP) and differential housing on territorial-induced aggression, locomotor activity, and monoamine neurochemistry in mice. Groups of male CF-1 mice were singly-housed or group-housed and administered a semisynthetic basal diet supplemented with TRP (0.25-1.0%). Behavioral measures were taken at various intervals up to 2 weeks after dietary administration was instituted. Separate groups of mice were given the same experimental treatment and sacrificed for whole brain determination of the monoamines and their metabolites. Isolated mice were consistently more aggressive than grouped animals, suggesting that territorial-induced aggression is synergistic with intermale aggression based on social isolation. The combination of isolation and 0.50% TRP was particularly effective in producing increases in aggression that reached maximal levels after 10 days of diet administration. However, motor activity of singly-housed mice was unaffected by TRP, while that of grouped mice was decreased after 5 days of 0.50% TRP. By day 14 of administration behavioral changes tended to return to baseline levels. Neurochemical measures indicated increased DA and 5-HT turnover in isolated mice, with the 5-HT system most affected by dietary TRP. Because housing conditions were a prominent factor in the aggression and neurochemistry, the results suggest the involvement of both transmitter systems in this behavior. However, there were no changes in monoamine turnover that could account for the development of behavioral tolerance.

Aggression↗
PubMed1990

Differences in children's peer sociometric and attribution ratings due to context and type of aggressive behavior.

Sociometric and attribution (internality and responsibility) ratings of boys performing different kinds of aggression (hostile and instrumental hitting and pushing) and of neutral behavior occurring in two contexts (provoked and unprovoked) were investigated in an analogue fashion. Thirty fifth- and sixth-grade boys viewed and rated 12 brief videotaped scenes of two unfamiliar male peers interacting, presented in one of six random orders. Provoked aggression resulted in less dislike, less worthiness of punishment, and greater attribution to external causes than unprovoked aggression. Instrumental and hostile aggression produced lower liking ratings and were viewed as more deserving of punishment than neutral behavior but did not differ from each other. Results support distinctions between provoked and unprovoked aggression but not between hostile and instrumental aggression, at least in terms of their functional impact on peer judgements.

Adolescent↗
PubMed1977

"Think aloud": a program for developing self-control in young aggressive boys.

"Think Aloud" was designed as a training program to improve self-control in 6- to 8-year-old boys. It involved modeling and verbalization of cognitive activity to foster use of verbal mediation skills in dealing with both cognitive and interpersonal problems. It was hypothesized that this training would lead to improvement in test performance and teacher ratings of classroom behavior in hyperaggressive boys. Twelve aggressive second grade boys participated in daily, 30-minute, individual sessions for 6 weeks. Normal and aggressive control subjects received no intervention. Teachers rated both trained and untrained aggressive boys as improving in aggressive behaviors but they rated the experimental group as showing improvement on a significantly larger number of prosocial behaviors. The pattern of performance on cognitive tests also changed significantly in the experimental group. On pretest, their pattern differed from normals and resembled the aggressive control group, while on posttest their pattern resembled normals and differed from agressive controls. Suggestions were made concerning additional refinements needed in the program, but overall results indicated potential value in the present approach for providing assistance to aggressive boys in the early grades.

Achievement↗
PubMed1990

Attributions for social failure and aggression in incarcerated delinquent youth.

While a variety of cognitive deficits and biases have been found to characterize aggressive and delinquent children and youth, very little attention has focused on determining whether aggressive youth also display deviant attributional beliefs in response to social failure. Research in the more impersonal cognitive domains such as achievement has shown attributions for failure to be potent determinants of both affective reactions and subsequent responding. Thus, the present study was designed to investigate whether specific attributional patterns following social failure may also relate to aggressive behavior. The aim of this study was to determine the relation between the level of self-reported physical aggression and specific attributional patterns following hypothetical social failure in a sample of incarcerated delinquent males. While the general hypotheses were that increased aggressiveness would be related to a greater tendency to endorse attributions for social failure that are external, stable, and controllable, only the hypothesis with regard to controllability was supported. The findings are discussed in terms of the relation between cognition and aggression in delinquent youth.

Adolescent↗
PubMed1981

Hyperactive and aggressive behaviors in childhood: intertwined dimensions.

The relationship between aggression and hyperactivity is unclear in childhood hyperkinesis. To examine the relationship between the two dimensions, a sample of 109 first-, second-, and third-grade children who were rated as hyperactive were evaluated daily by their teachers for 12 consecutive school days on the Daily Behavior Checklist. Daily recordings were made on a total of 22 specific behaviors, 11 physically or verbally aggressive acts, and 11 acts of a restless or hyperactive nature. The Conners hyperactivity score correlated .47 with daily aggression and .49 with daily hyperactivity. A subgroup of hyperactive children who exhibited both hyperactive and aggressive behaviors at rates greater than 98% of their classmates was selected. These children were rated significantly higher on the Conners scale than on alternate subgroup of hyperactive children who showed high rates of hyperactive but not aggressive behaviors. In view of heavy reliance on teacher ratings with the Conners scale in studies of hyperactivity, careful consideration of the potential confounding of hyperactivity and aggression is recommended. Implications for classification, longitudinal investigation, and evaluation of treatment of hyperactive children were discussed.

Age Factors↗
PubMed1990

Attributional style in aggressive adolescent boys.

Past research suggests that aggressive children misattribute hostile intentions to peers during ambiguous provocative interactions. This study sought to extend the analysis of attributional differences between aggressive and nonaggressive boys to a sample of court-involved adolescents and their perceptions of interactions involving both peers and adults. Three groups of youngsters (nonoffenders, nonaggressive offenders, and aggressive offenders) participated in a structured interview and provided causal attributions for interpersonal problems commonly faced by teenagers. Results indicated that offenders were more likely than nonoffenders to attribute blame to others in ambiguous problem situations. Among offenders, external, person-centered blame attributions were significantly related to aggressiveness. This relationship was found only in ambiguous situations, and the correlation between such person-centered attributions and aggressiveness was higher in adult-oriented interactions than in peer-oriented ones. Overall, the results suggest that aggressiveness among offenders is associated with an attributional style that is characterized by the tendency to attribute blame for problems in ambiguous interactions to global, dispositional characteristics of others.

Adolescent↗
PubMed1983

Measuring physical aggressiveness in heterosexual, homosexual, and transsexual males.

The purpose of this study was the development of a self-report measure of boyhood aggressiveness for use with adult males. Aggressiveness was defined as a generalized disposition to engage in physically combative or competitive interactions with male peers. This attribute is of sexological interest because of the reported difference in physical aggressiveness between heterosexual and homosexual boys. A physical aggressiveness scale (PAS) was constructed from items regarding boyhood athletic interest and proficiency, as well as fighting with and feelings of unease around male peers. The PAS and Part A of the Feminine Gender Identity Scale for males (FGIS(A), Freund et al., 1977) were administered to 193 adult men. The PAS was shown to be reliable and factorially pure. The PAS scores of homosexuals were significantly lower than those of heterosexuals, and the scores of male-to-female transsexuals were lower yet. No differences were found among three heterosexual groups: prison inmates and nonuniversity- and university-educated males. Precisely symmetrical results were obtained with the FGIS(A), with the male-to-female transsexuals scoring highest and the heterosexuals lowest. Group differences in FGIS(A) scores were greater than those in PAS scores; this was interpreted as possible evidence that physical aggressiveness is more sensitive than gender identity to variables uncorrelated with erotic preference, e.g., perceptual-motor ability, rate of physical maturation, etc. The main results suggest that whatever underlying factor relates homosexuality to feminine gender identity in childhood relates this erotic preference to anomalously low levels of physical aggressiveness in childhood as well.

Adult↗
PubMed1995

Aggressiveness, dominance, developmental factors, and serum cholesterol level in college males.

The present study was conducted to examine for college males relations between aggressiveness (or expressive hostility) and dominance and (a) particular developmental experiences and (b) total serum cholesterol. Aggressiveness but not dominance was found to be positively related to subjects' reports of their parents' behavior which reflected (a) less genuine acceptance, (b) more interference in the person's desires as a child, and (c) more punitiveness. For low-physically fit subjects, both aggressiveness and dominance were found to be positively related to levels of total serum cholesterol. These relations are congruent with the notion that both aggressiveness and dominance may contribute to hastening coronary atherosclerosis and risk of CHD via elevated levels of plasma lipids. It should be noted, however, that the relations obtained in the present study were all modest in size. For high-physically fit individuals associations were not found between total serum cholesterol and either aggressiveness or dominance. These results suggest that good physical fitness may attenuate the degree to which either aggressiveness or dominance may adversely affect health via elevated levels of cholesterol.

Adolescent↗
PubMed1993

Prevention of the pro-aggressive effects of alcohol in rats and squirrel monkeys by benzodiazepine receptor antagonists.

Pharmacological manipulations at the benzodiazepine-GABAA-chloride ionophore receptor complex modify some of the behavioral and physiological actions of alcohol (ethanol). The interactions between alcohol, benzodiazepines and aggression were examined in similar ethopharmacological studies in squirrel monkeys and in rats in confrontations with conspecifics. Dominant male squirrel monkeys were tested (1) within their social groups, and (2) in dyadic confrontations with "rival" males from a different social group, and resident male rats were tested in their home cage in confrontations with an inexperienced male intruder. Low doses of alcohol (0.1-0.3 g/kg) increased aggressive behaviors in dominant squirrel monkeys and a subgroup of resident rats, whereas high doses of alcohol (1-3 g/kg) decreased aggression and produced marked motor incoordination. Individuals that showed alcohol-enhanced aggression were selected, and pretreated with benzodiazepine antagonists (flumazenil, ZK 93426) prior to alcohol administration. Both ZK 93426 (3 mg/kg) and flumazenil (10 mg/kg) blocked the aggression-enhancing effects of alcohol in dominant squirrel monkeys and resident rats in confrontations with conspecifics. Neither compound altered the reductions in aggression and increases in inactivity produced by high doses of alcohol. Interestingly, agonist-like increased feeding and inverse agonist-like reductions in social behaviors were observed simultaneously at the same dose of flumazenil, in the same individual and testing situation. ZK 93426 did not alter feeding but also reduced social behaviors. The two antagonists were also not equipotent in their interactions with alcohol. ZK 93426 reduced alcohol-induced motor incoordination in squirrel monkeys, whereas flumazenil did not. In fact, flumazenil potentiated the effects of low doses of alcohol.(ABSTRACT TRUNCATED AT 250 WORDS)

Aggression↗
PubMed1993

Aggression modulates genetic influences on morphine analgesia as assessed using a classical mendelian cross analysis.

Pharmacogenetic techniques allow for the examination of genetic and environmental factors underlying phenotypes associated with drug response. Initial studies of mice bred at Jackson Laboratories (JAX) indicated that C57BL/6J mice were more sensitive to morphine-induced analgesia, as measured by latency to paw lick, than SJL/J mice. A classical Mendelian cross breeding program was initiated in which F1, F2 and backcross generations were derived from C57BL/6J and SJL/J breeding pairs purchased from JAX to examine the genetic factors underlying morphine analgesia. Genetic analysis indicated significant dominance or heterosis for a reduced drug response. The F1 generation was less sensitive to morphine-induced analgesia than either parental strain. Mathematical analysis of the generation means revealed that a simple dominance model with no epistatic interaction between genes best described the data. Environmental factors also affected sensitivity to morphine analgesia, in that C57BL and SJL mice raised in our facility did not differ in latency to paw lick. SJL mice from JAX exhibit a high degree of aggression, while SJL mice raised in our facilities show little or no aggression. The levels of aggression among groups of SJL mice were characterized and found to correlate with sensitivity to morphine analgesia. Mice exposed to increasingly greater levels of aggression were the least sensitive to morphine. Thus, the changes observed in sensitivity to morphine-induced analgesia appear to be related to the degree of aggression to which these mice are exposed, possibly resulting from the stress and/or prolonged exposure to painful stimuli associated with aggressive encounters.

Aggression↗
PubMed1996

Studies on wild house mice. VII. Prenatal maternal environment and aggression.

The effect of the maternal environment on intermale aggression was studied by means of embryo transfer of genetically selected aggressive (SAL) and nonaggressive wild house mice (LAL), and their reciprocal F1's, to standard (NMR1) females. No effect was found on the attack latency scores (ALS), i.e., aggression: all genotypes born and raised under natural conditions showed an ALS similar that of genotypes born and raised by NMR1 females. Since previous studies on wild house mice failed to demonstrate postnatal effects on aggression, and the present results indicate the absence of prenatal maternal environmental effects on aggression, the primacy of genetic over maternal variance in the development of adult intermale aggression in wild house mice is indicated.

Aggression↗
PubMed2004

Fluoxetine increases relative metabolic rate in prefrontal cortex in impulsive aggression.

RATIONALE: Impulsive aggressive personality disordered patients have been shown to have decreased relative glucose metabolism in orbito-frontal cortex and anterior cingulate gyrus compared with normal subjects. In addition, patients with impulsive aggression have an attenuation of symptoms with selective serotonin reuptake inhibitor (SSRI) treatment. OBJECTIVES: The goals of the present study were to attempt to replicate the finding of improvement in impulsive aggression in borderline personality disorder with SSRIs and to investigate the specific cortical areas modified by medication, which might underlie the observed clinical improvement using (18)FDG-PET. METHODS: Ten impulsive aggressive patients with borderline personality disorder were imaged with (18)F-deoxyglucose positron emission tomography at baseline and after receiving fluoxetine at 20 mg/day for 12 weeks. Anatomical MRIs were coregistered to PET and relative metabolic rates were obtained in 39 Brodmann areas. RESULTS: Brodmann areas 11 and 12 in the orbito-frontal cortex showed significant increases in relative metabolic rate. Significant clinical improvement was also observed as assessed by the Overt Aggression Scale-Modified. CONCLUSIONS: These changes are consistent with a normalizing effect of fluoxetine on prefrontal cortex metabolism in impulsive aggressive disorder.

Adult↗
PubMed2003

Estimates of regional cerebral blood flow and 5-HT2A receptor density in impulsive, aggressive dogs with 99mTc-ECD and 123I-5-I-R91150.

Impulsive aggression in dogs has an important impact on human public health. Better insight into the pathophysiology of this phenomenon could lead to more adequate diagnosis and treatment. Indirect in vivo research on peripheral body fluids and post-mortem studies in impulsive animals and humans indicate a deficient serotonergic system in general and disturbances in the serotonin-2A (5-HT2A) receptor in particular. In this study, brain perfusion and the 5-HT2A receptors were examined in impulsive, aggressive dogs, in comparison with a group of normally behaving animals. In order to decide which dogs to include in this study, owners were asked to describe the general behaviour of the dogs, the circumstances in which aggression occurred and their conduct during aggressive acts. Finally, 19 dogs were retained for this study, showing, according to different behavioural specialists, disinhibited dominance aggression. Functional imaging studies were performed on all these dogs. Single-photon emission tomography (SPET) was used to measure regional brain perfusion using technetium-99m labelled ethyl cysteinate dimer (ECD). The 5-HT2A receptor binding properties were investigated using the selective radioligand iodine-123 labelled 5-I-R91150. A significant increase in uptake of the 5-HT2A radioligand was noted in all cortical areas. No significant alterations were found in regional cortical perfusion, indicating that the increased binding index was not a consequence of increased tracer delivery. This study supports a role for the serotonergic system in canine impulsive aggression.

Aggression↗
PubMed2003

Experience-based plasticity of acoustically evoked aggression in a territorial frog.

Territorial male bullfrogs ( Rana catesbeiana) display lower levels of aggression toward familiar territorial neighbors compared to unfamiliar individuals based on the perception of individual differences in vocalizations. Stimulus-specific habituation elicited by repeated exposures to a neighbor's vocalizations is believed to play a role in mediating the low levels of aggression between neighbors. The present study describes habituation in multiple components of the bullfrog territorial aggressive response and examines whether these separate response components habituate at similar or different rates. In response to repeated broadcasts of synthetic bullfrog advertisement calls in a field playback experiment, the numbers of aggressive calls and movements, the latency to the first aggressive call, and the distance approached toward the playback speaker exhibited significant response decrements that developed at nearly identical rates. All four responses exhibited recovery upon subsequent broadcasts of a novel stimulus simulating a different individual. In contrast, the number of advertisement calls did not exhibit significant decrements with repeated playbacks. The patterns of stimulus-specific response decrement were inconsistent with explanations such as sensory adaptation, effector fatigue, non-specific changes in motivation, and a simple form of auditory habituation. Possible mechanisms for the observed plasticity in aggression are discussed in the context of anuran communication.

Acoustic Stimulation↗