Amygdaloid function in the central cholinergic mediation of shock-induced aggression in the rat

A series of experiments was designed to examine the role of central cholinergic mechanisms in shock-induced aggression. Cholinergic blockade in the basolateral amygdala, ventral hippocampus, or dorsal hippocampus resulted in greatly reduced levels of fighting in response to footshock. However, while pain sensitivity remained unaltered in the amygdala group, both of the hippocampal groups exhibited decreased shock sensitivity. Further investigation of the amygdala revealed (1) increased fighting in response to increased cholinergic levels, (2) neuroanatomical specificity to the basolateral division of this complex, (3) that an intact basolateral amygdala is essential to the normal manifestation of shock-induced aggression, and (4) that social attraction remains unaltered by cholinergic blockade of the basolateral amygdala. Motor coordination and motor activity were not significantly affected in any treatment condition.     

Effects of some physiological and pharmacological manipulations on shock- facilitated mouse killing by onychomys leucogaster (Northern grasshopper mouse)

Onychomys leucogaster (northern grasshopper mice) were induced to kill mice with response-contingent shock, and the effects of several physiological, pharmacological, and endocrinological variables were assessed. Lesions of the septum facilitated mouse killing, while lesions of the amygdala abolished spontaneous mouse killing and delayed shock-facilitated killing. Chlorpromazine (2.5–5 mg/kg) and chlordiazepoxide (5–10 mg/kg) facilitated mouse killing on postdrug trials but did not affect killing when the animals were drugged. Adrenalectomy, castration, and castration adrenalectomy did not alter the frequency of kill nor were sex-related differences in killing noted. These results were compared to those found by others studying the effects of lesions and drugs on mouse killing by rats.     

Competitive fighting for shells in the hermit crab,Clibanarius vittatus

The aggressive behavior of large Clibanarius vittatus against small C. vittatus was investigated. Large C. vittatus were more aggressive and showed fewer fear reactions in all conditions tested. The degree of dominance of large over small C. vittatus was much more marked and more predictable when the smaller crab occupied a Polinices rather than a Littorina shell and the large crab occupied a Littorina shell in both conditions. Evidence is given to suggest that C. vittatus reacts more to the shape than the size dimensions of a Polinices shell, and that small crabs occupying a Polinices shell are less active than other crabs occupying a Littorina shell.     

Enhanced social docility in male hooded rats by dermal cautery of the vibrissal pads

Ablation of the vibrissal pads in rats causes subsequent deposition of scar tissue with little or no regrowth of the vibrissae. Cauterized and intact mature male Long Evans rats were tested for shockelicited fighting, mouse killing, and colony intrusion forms of laboratory-induced aggression. The results revealed that only conspecific social fighting is blocked by ablation of the major vibrissal follicles. Although no significant group differences were noted in tests for mouse killing, shock-elicited paired fighting and territorial defense against a strange intruder were minimal in cauterized groups. The results emphasize the importance of specific sensory experience in reference to distinct forms of aggressive responding and support a new experimental technique for further investigation of sensory interactions with sources of aggressive behavior.     

Effects of the cholinomimetic drug arecoline upon aggression: Intra- vs. inter-specific allocation of attack

Systemic injections of cholinomimetic drugs have been reported to induce both rage and predatory attack in several species. In order to assess the relative contribution of each of these two behavioral patterns in the control of cholinergically induced attack, a group of adult female cats was chemically stimulated in the simultaneous presence of both a prey object and a conspecific attack object. In this choice situation stimulated cats initially tended to engage in rage attack. When a second group of subjects was tested in a successive choice situation a significantly greater number of attacks occurred against conspecifics. The results suggest that cholmergic stimulation initially induces affective attack, with somewhat less frequent incidents of predation.     

Effects of age at differential housing and the duration of individual housing/grouping on lntermale fighting behavior and adrenocortical activity in TO strain mice

A study of the effects of the duration of individual and group housing on intermale fighting and adrenocortical activity was conducted in TO strain mice. It was found that fighting and threat increased with progressive isolation up to an asymptote at 56–58 days. ‘Basal’ adrenocortical function differed little under the 2 housing conditions, but after ‘stress,’ mice isolated for short periods, which had not fought when tested for aggression, had lower titers than group-housed counterparts. However, mice that had been isolated for longer periods, and had fought in aggression tests, had higher corticosterone titers than comparable group-housed animals. The effects of a short duration (28–30 days) of differential housing, commencing at different ages, were also studied. The shorter duration adrenocortical changes were largely confirmed. In general, the earlier the age at which the differential housing was imposed, the greater the behavioral differences between animals under each housing condition. It is suggested that this is largely a consequence of a loss of behavioral plasticity in older mice. The data provides little support for the concept of the “isolation stress syndrome,” or for the view that the characteristic fighting exhibited by individually housed mice is a consequence of “social deprivation”.     

The introduction of a group of alien mice (Mus musculus L.) into hierarchically organized groups of five male mice

Groups of 3 male or female Mus musculus were introduced into hierarchically organized colonies of 5 male mice for a period of 8 days. The colonies were of 2 kinds; high-level aggressive (HLA), which had been set up 3 days prior to the introduction of the aliens, and low-level aggressive (LLA), which had been established for 21 days before strangers were introduced. Both males and anestrous females were attacked, but males were attacked 5 times more frequently than females. In HLA colonies most of the attacks on the aliens were by the dominant; in LLA colonies there was no difference in the behavior of dominant and subordinate mice toward strangers. Both aggression toward aliens and intracolony aggression declined over the 8 day experimental period. In HLA colonies the dominant mouse mounted females 5 times more frequently than did either his subordinates or male mice in the LLA colonies. In HLA colonies aliens huddled with subordinates to form a single colony with 1 dominant and 7 subordinates. In LLA colonies alien males remained as a discrete group spatially separated in the cage. Female aliens were incorporated into the main colony. In all cases dominant male mice made more attacks on aliens as compared with familiar mice.     

Hostility in fantasy: A further test of the hypoglycemia-aggression hypothesis

In a recent investigation carried out among the Qolla Indians of Peru, Bolton (1973a) tested the hypothesis that hypoglycemia tends to produce high levels of individual aggressiveness. Glycemic condition was determined by the readings on a 4-hour glucose tolerance test performed on a sample of 54 adult males. Key informants then ranked these subjects on overt aggressiveness. A correlational analysis of the data supported the hypothesis that moderately hypoglycemic subjects would be more aggressive than the normoglycemic subjects. The present paper responds to questions raised about this study and describes the results of an additional test of the hypoglycemia-aggression hypothesis. The dependent variable in this follow-up study is fantasy aggression. Aggression scores were derived from Sentence Completion Test protocols for the same sample of subjects used in the first study. The results indicate a significant correlation between glycemic condition and aggression scores (Biserial, 0.57), thus providing further confirmation of the hypoglycemia-aggression hypothesis.     

Rank and reproduction among female langur monkeys: Aging and improvement (They're not just getting older,they're getting better)

An investigation of the social rank, reproduction, and ages of adult female Indian gray langur monkeys (Presbytis entellus) living in two colony social groups revealed that rank based on displacements is neither correlated with nor best predicted by female age or reproductive value. The hierarchy of female ranks is best conceptualized as a layered ranking system in which there are clusters of females of the same dominance rank forming layers within the structure. Statistical significance in frequencies of displacement differs between but not within these layered groups of females. Factors such as group composition, presence of uterine kin, reproductive state, and individual personality are hypothesized to predict changes in female rank far better than does reproductive value. Our data show that reproductive success increases with age. The infant survival record for the six oldest females in our colony was much better than for the five youngest adult females.     

Attack and defensive behaviors in the albino mouse

Attack by dominant male colony mice on intruders included chasing and lateral attack behaviors, while the corresponding intruder behaviors were flight, boxing, and checking. Both of these are similar to the attack and defensive behaviors of colony rats and intruders. However, mice did not show a significant constraint on bites to ventral areas, and the rat defensive behavior of lying on the back, which is effective because of this constraint, was rare; the corresponding “on-top” behavior of attackers was almost absent in mice. These findings strongly support the view that intraspecific attack and defensive behaviors, and target sites for bites, are interrelated factors facilitating effective but nonlethal agonistic interactions in muroid rodents.