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Biomedical subjects

R F Benus

Publications and source records attributed to R F Benus.

4 recordsLinked to original sources
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↗
PubMed1991

Behavioural differences between artificially selected aggressive and non-aggressive mice: response to apomorphine.

The present study reports a first attempt to unravel the neurochemical background that underlies the difference in behavioural profiles between aggressive and non-aggressive male mice. For this purpose two bidirectionally selected lines for attack latency (SAL and LAL) were used. In pursuit of Cools'9 approach, the susceptibility of individuals of both selection lines to the dopamine agonist apomorphine was measured. The apomorphine was injected subcutaneously at dose levels of 2.5 and 5.0 mg/kg. Apomorphine is considered to stimulate the dopamine receptors in the telencephalon and induces stereotyped behaviour. The responsivity to apomorphine can be rated as a total stereotypy-score. SAL (aggressive) mice showed a significantly greater enhancement of stereotyped behaviour in response to apomorphine than LAL (non-aggressive) mice. In addition, it was demonstrated that this difference is of a quantitative rather than qualitative character. Pharmacokinetic variation between the two lines could be ruled out as cause of the difference. Hence, it was concluded that SAL mice are more sensitive to apomorphine than LAL males, which provides evidence for a difference in the dopaminergic system between the two selection lines. It was suggested that this difference underlies the difference in flexibility in behaviour between aggressive and non-aggressive male mice.

Aggression↗
PubMed1988

Aggression and adaptation to the light-dark cycle: role of intrinsic and extrinsic control.

In wild house mice, the hypothesis that in the organization of behavior the relative contribution of intrinsic factors is more important in aggressive males, while that of extrinsic factors is more important in nonaggressive individuals was confirmed using the circadian rhythmicity of activity. The faster rate of reentrainment and the suppression of activity during a subjective night and during adaptation to the new LD cycle in the nonaggressive males indicate that their circadian rhythmicity of activity is to a large extent determined by the Zeitgeber, an extrinsic factor. The slower reentrainment rate, the lack of response to a subjective night and the normal activity level seen during reentrainment in the aggressive mice suggest strong control by the pacemaker, an intrinsic factor. Tau differences between the aggressive and nonaggressive mice provide some evidence that the pacemaker of nonaggressive males is fairly labile and is easily influenced by external factors, whereas the pacemaker of aggressive animals is rather stable.

Acclimatization↗