Paul F. Brain

Bullying in schools: Lessons from two decades of research

Bullying is described as aggressive behavior normally characterized by repetition and imbalance of power, It may be considered as a normative in many group settings, but socially unacceptable within the ethos of a democratic society, The history of research and intervention on bullying in schools during the past two decades is summarized, School bullying emerges as an international issue, and we have increasing knowledge of its nature and effects, There is also growing experience of the effectiveness of a range of school-based intervention strategies, These issues are discussed in relation to the 10 articles from 9 countries that constitute the remainder of this Special Issue on Bullying in Schools,

What does individual housing mean to a mouse

Abstract Some recent studies relating the effects of individual housing (isolation) and group housing to behavior, physiology and neurochemistry in laboratory rats and mice are reviewed and these accounts related to comparable information derived from experiments employing “social stresses” e.g. subjecting the animal to defeat. The data is discussed in relation to the problem of whether individual housing constitutes a “stress” (in terms of adrenocortical and adrenal medullary functioning) in these species, as it appears to do in primates. In spite of the large number of papers which ascribe the behavioral and endocrine changes obtained in isolation versus grouping comparisons to the effects of “the isolation-induced stress syndrome”, it is concluded that, in terms of adrenal function, there is little evidence that isolation per se constitutes a stress in rats and mice, although there is some evidence that adrenocortical reactivity is increased by housing animals in this manner. It should be noted that the wild progenitor of the laboratory strains of house mouse often appears to evidence territoriality. The view is advanced that the isolated condition in male mice may result in changes characteristic of territorial dominance. This may represent a mechanism for inducing social or territorial stability in this species. It appears that experiments involving physical isolation in laboratory rodents are unlikely to provide good models for the effects of “social deprivation” in man. It is thought that more studies employing measurement of hormone titers in biological samples, obtained as a result of non-stressful procedures, will lead to a clearer understanding of the effects seen in isolation versus grouping studies. Organ weight studies often appear to be very misleading, particularly in female rodents. It is also hoped that other studies will concern themselves with effects of isolation with respect to other social cues in rodents including odors and ultrasound.

Effects of chronic mild stress on performance in behavioural tests relevant to anxiety and depression

Chronic exposure to mild unpredictable stress (CMS) has previously been found to depress the consumption of a weak (1%) sucrose solution by rats. This effect was confirmed in each of three experiments in the present study, following which behaviour was examined in other tests relevant to either depression or anxiety. CMS did not significantly affect behaviour in the social interaction test and caused an anxiolytic-like profile in the elevated plus-maze. CMS increased submissive behaviour in the resident-intruder test, and decreased male sexual behaviour. The latter effect was more pronounced in animals reared in isolation from the time of weaning; isolation rearing did not influence sexual behaviour in nonstressed animals. Isolation rearing also potentiated the effect of CMS on sucrose drinking, in both male and female rats. These results support the relevance of the CMS procedure as a potential animal model of depression.

Corticosterone response to the plus-maze: High correlation with risk assessment in rats and mice

Exposure to the elevated plus-maze induces behavioural and physiological effects in rodents consistent with fear/anxiety. Maze-naive animals display high levels of risk assessment towards the open arms, and explore these areas less extensively than other parts of the maze while, immediately following the test, pain latencies, skin conductance levels, and plasma corticosterone titres (CORT) are significantly elevated. Although previous research has suggested a link between the plasma CORT response and open-arm exploration, significant elevations in CORT have also been found with restricted exposure to the closed arms. The present study employed ethological measures in an attempt to further characterise the relationship between behavioural and CORT responses to this widely used animal model of anxiety. Our results confirm that, relative to home-cage controls, 5-min exposure to the plus-maze significantly increases plasma CORT levels in test-naive male Wistar rats and male Swiss-Webster mice. Furthermore, in both species, the CORT response was found to be highly correlated with measures of risk assessment (mice: rs = +0.87; rats: rs = +0.58), but not with measures of open-arm activity (entries, time), general locomotor activity, rearing, or head dipping. Findings are discussed in relation to the functional significance of risk assessment in potentially dangerous situations and the potential involvement of glucocorticoids in this process. All rights reserved.

Attenuation of sucrose consumption in mice by chronic mild stress and its restoration by imipramine

Chronic exposure to mild unpredictable stressors (CMS) has previously been found to reduce the consumption of palatable, sweet solutions in rats. In the present study, the utility of this procedure was assessed in mice. Male AP mice subjected to CMS showed reduced consumption of a 2% or 4% sucrose solution. This effect was reversed by chronic (3 weeks) treatment with the tricyclic antidepressant imipramine (20 mg/kg per day). These results extend previous reports of a generalized decrease in sensitivity to reward (anhedonia) in rats caused by CMS and the efficacy of antidepressant treatment in this paradigm. Chronic unpredictable mild stress in mice appears to provide a realistic animal model of depression.

The interpretation of physiological correlates of differential housing in laboratory rats

Abstract A critical review is presented of studies in which (for one reason or another) physiological measures in individually-housed rats are contrasted with those of group-housed counterparts. Most studies seem to focus on adrenocortical activity; gonadal hormone secretion and estimation of localized putative neuro-transmitters. An attempt is made to link these factors and to correlate them with the well-documented behavioral changes seen in ‘isolated’ rats. It is concluded that it is possible that the changes in biogenic amines and hormones are related. It seems unlikely, however, that one can dismiss the physiological changes seen in individually-housed rats as ‘isolation stress’. Adrenocortical reactivity may be increased in ‘isolated’ rats and this may account for their apparent increased basal activity. It is concluded that there is a distinct lack of ‘in depth’ studies in this area.

Steroid hormone-induced effects on membrane fluidity and their potential roles in non-genomic mechanisms.

Steroid hormones are lipophilic suggesting they intercalate into the bilayer of target cell plasma membranes, potentially altering the fluidity and function of the membrane. The present study measured the effects of steroidal exposure on both phospholipid fluidity and integral protein mobility. Studies were performed on the effects of a variety of steroids on phosphatidylcholine liposomes, synaptosomal plasma membranes and sarcoplasmic reticulum membranes. Progesterone decreased the lipid fluidity, whereas testosterone had no effect on lipid movement. The estrogen, 17 beta-estradiol, an aromatised metabolite of testosterone, increased lipid mobility. In each case, the steroid action was concentration-dependent. The steroids all increased the activity of the Ca2+ ATPase of SR membrane, in keeping with their effects on this enzymes aggregation state. The results suggest that, although lipid fluidity is a factor influencing protein activity, their mobility within the bilayer is the primary determinant of enzyme activity in the membrane for most proteins.

Correlating testosterone and fighting in male participants in judo contests

The role of hormones in human aggression is open to debate, but takes on a new urgency owing to the alarming abuse of androgenic anabolic steroids by some sports participants. In this study, video-taped behavior exhibited by 28 male competitors during a judo fight was assessed to analyze its relation to serum testosterone and cortisol levels measured before and after the bouts. A positive relation between testosterone and offensive behaviors was obtained in the sense that the greater the hormonal titer, the greater the number of threats, fights, and attacks. These findings coincide with the pattern of relationships found using observational scales. Conversely, cortisol also presented positive correlations with some of these behavioral categories but did not moderate the relationship between testosterone and competitive behavior. The present results corroborate and extend earlier findings on the role of these hormones in human behavior, giving support to the view that testosterone can be linked to the expression of competitive aggression.

Glucose improves attention and reaction to frustration in children

There have been many suggestions that both dietary sugar and the level of blood glucose may be associated with abnormal behaviour. To examine this question 60 six- and seven-year old children were given a drink that contained either 25 grams of glucose or a placebo towards the end of the school day. They were then subjected to one test that required sustained attention and to a second that was intentionally frustrating. Those given the drink containing glucose were more capable of sustaining attention and showed fewer signs of frustration.

Effects of chronic mild stress (CMS) and imipramine administration, on spleen mononuclear cell proliferative response, serum corticosterone level and brain norepinephrine content in male mice

There is increasing evidence that stress and emotional reactions produce changes in various immune processes. These changes may be due to alterations of the stress responses endocrine and for autonomic mediating mechanisms. In order to study such effects, the impact of chronic mild stress (CMS) application, and of subsequent imipramine administration were studied on the spleen mononuclear cell proliferative response period. OFI strain male mice were subjected to 4 or 7 weeks of CMS. The effects of these treatments on serum corticosterone levels and hypothalamic and hippocampal norepinephrine (NE) contents were also assessed. Subjects submitted to CMS had a higher spleen mononuclear cell proliferative response after either treatment duration. Imipramine treatment diminished this response enhancement in CMS exposed animals, but did not alter the proliferative responses of control subjects. Serum corticosterone levels, as well as hypothalamic and hippocampal nonrepinephrine contents did not significantly vary between groups. Taken together, these results suggest that CMSs effects on immune reactivity are not related to serum glucocorticoids or NE changes in these locations associated with the hypothalamic-pituitary- adrenocortical (HPA) axis.