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.

Patterns of violent aggression-induced brain c-fos expression in male mice selected for aggressiveness

Mice selected for aggressiveness (long and short attack latency mice; LALs and SALs, respectively) constitute a useful tool in studying the neural background of aggressive behavior, especially so as the SAL strain shows violent forms of aggressiveness that appear abnormal in many respects. By using c-Fos staining as a marker of neuronal activation, we show here that agonistic encounters result in different activation patterns in LAL and SAL mice. In LALs, agonistic encounters activated the lateral septum, bed nucleus of stria terminalis, medial amygdala, paraventricular nucleus of the hypothalamus, anterior hypothalamic nucleus and tuber cinereum area (both being analogous with the rat hypothalamic attack area), dorsolateral periaqueductal gray, and locus coeruleus. This pattern is similar with that seen in the territorial aggression of male mice, rats and hamsters, and non-lactating female mice. SALs showed strong fight-induced activations in the central amygdala and lateral/ventrolateral periaqueductal gray. In this strain, no activation was seen in the lateral septum and the dorsolateral periaqueductal gray. This pattern is similar with that seen in other models of violent aggression, e.g., in attacks induced by hypothalamic stimulation in rats, quiet biting in cats, lactating female mice, and hypoarousal-driven abnormal aggression in rats. We suggest here that the excessive activation of the central amygdala and lateral/ventrolateral periaqueductal gray--accompanied by a smaller activation of the septum and dorsolateral periaqueductal gray--underlay the expression of violent attacks under various circumstances.

'One-trial sensitization' to the anxiolytic-like effects of cannabinoid receptor antagonist SR141716A in the mouse elevated plus-maze

Significant variability in the effects of cannabinoid CB1 receptor ligands on emotional reactivity in animals and humans suggests that the endocannabinoid system may selectively modulate certain types of anxiety. In view of substantial evidence for qualitative differences in the nature of anxiety elicited on initial and subsequent exposures to the elevated plus-maze, the present studies contrasted the behavioural effects of the selective CB1 receptor antagonist SR141716A (0.1-10.0 mg/kg) and the reference benzodiazepine chlordiazepoxide (CDP, 15 mg/kg) both in maze-naive mice (trial 1) and in mice that had been given a single undrugged exposure to the maze 24 h prior to testing (trial 2). Results confirmed the anxioselective effect of CDP on trial 1 but a complete absence of such activity on trial 2 (i.e. one trial tolerance). In marked contrast, SR141716A had no behavioural effects in maze-naive mice but, at doses of 1.0-3.0 mg/kg (effect maximal at 1.0 mg/kg), significantly reduced anxiety-like responses in maze-experienced animals. Like the effect of CDP on trial 1, the antianxiety profile of SR141716A on plus-maze trial 2 was observed in the absence of any change in general activity levels. The apparent experientially induced 'sensitization' to the anxiolytic-like effects of SR141716A in the plus-maze contrasts markedly with the widely reported loss of benzodiazepine efficacy in test-experienced animals. Data are discussed in relation to the recently described phenotypes of CB1 receptor knockout mice and, in particular, to mounting evidence for the existence of a novel SR141716A-sensitive neuronal cannabinoid receptor.

Acute effects of glucocorticoids: behavioral and pharmacological perspectives

There has been evidence since the early eighties that glucocorticoids, apart from their well known chronic effects, may have acute, short-term effects. However, a lack of understanding of the molecular mechanisms of action has hampered appreciation of these observations. Mounting evidence over the years has continued to confirm the early observations on a fast corticosterone control of acute behavioral responses. We summarize experimental data obtained mainly in rats but also in other species which show: (1) that glucocorticoid production is sufficiently quick to affect ongoing behavior; (2) that there exist molecular mechanisms that could conceivably explain the fast neuronal effects of glucocorticoids (although these are still insufficiently understood); (3) that glucocorticoids are able to stimulate a wide variety of behaviors within minutes; and (4) that acute glucocorticoid production (at least in the case of aggressive behavior) is linked to the achievement of the behavioral goal (winning). The achievement of the behavioral goal reduces glucocorticoid production. It is argued that glucocorticoids are regulatory factors having a well-defined behavioral role. Both the acute (stimulatory) effects and the chronic (inhibitory) effects are adaptive in nature. The acute control of behavior by corticosterone is a rather unknown process that deserves further investigation. The pharmacologic importance of the acute glucocorticoid response is that it may readily affect the action of pharmacologic agents. An interaction between acute glucocorticoid increases and noradrenergic treatments has been shown in the case of offensive and defensive agonistic behavior. Non-behavioral data demonstrate that acute increases in glucocorticoids may interfere with other neurotransmitter systems (e.g., with the 5HT system) as well. These observations show the importance of taking into account endocrine background and endocrine responsiveness in behavior pharmacological experiments.

Ultradian corticosterone rhythm and the propensity to behave aggressively in male rats

Ultradian fluctuations in plasma glucocorticoids have been demonstrated in a variety of species including humans. The significance of such rhythms is poorly known, although disorganized ultradian glucocorticoid rhythms have been associated with behavioural disorders. Here we report that ultradian glucocorticoid rhythms may establish the propensity to behave aggressively in male rats. Male rats were significantly more aggressive in the increasing phase of their corticosterone fluctuation when confronting a male intruder than counterparts in the decreasing phase of their corticosterone fluctuations facing such opponents. Corticosterone fluctuations were mimicked by a combination of treatments with the corticosterone synthesis inhibitor metyrapone and corticosterone. Again, males with increased plasma corticosterone levels were more aggressive than counterparts with a decreased plasma corticosterone concentration. These data suggest that the behavioural response to an aggressive challenge may vary in the same animal across the day due to the pulsating nature of corticosterone secretion. Aggressive behaviour is also episodic in humans; moreover, intermittent explosive behaviour is recognized as a psychological disorder. It can be hypothesized that a temporal coincidence between the occurrence of a challenge and a surge in plasma corticosterone concentration may be one of the factors that promote episodic aggressive outbursts.

Serum S100B and neuron-specific enolase levels in normothermic and hypothermic infants after perinatal asphyxia

AIM

Serum S100B and neuron-specific enolase (NSE) levels are elevated after perinatal asphyxia, but the influence of hypothermia on these proteins has not been previously reported. The aim of this study was to evaluate the effect of systemic hypothermia on these protein levels after perinatal asphyxia, time course, and association with perinatal factors and neurodevelopmental outcome at 2 years of age.

METHODS

Serum S100B and NSE levels were measured at fixed time points in asphyxiated infants treated with standard intensive care on hypothermia (HT: n = 13) or normothermia (NT: n = 11).

RESULTS

Serum S100B and NSE levels were grossly elevated in both HT and NT groups. Compared with the values at 6 h of age, S100B values decreased over time in both groups (NT: p = 0.002, HT: p = 0.04). Serum S100B values were lower in HT infants compared with those in NT infants (p = 0.047 at 48 h). Serum S100B and NSE values were significantly higher in infants who died or developed severe neurological impairment (S100B, p < 0.05 at all time points; NSE, p = 0.036 at 24 h of age).

CONCLUSION

Both NSE and S100B levels are highly elevated following asphyxia. Serum S100B levels were lower in the HT group and strongly correlated with the neurodevelopmental outcome.

The effect of neurokinin1 receptor blockade on territorial aggression and in a model of violent aggression

BACKGROUND

Neurokinin1 (NK1) receptor blockers were recently proposed for the treatment of anxiety and depression. Disparate data suggest that NK1 receptors are also involved in the control of aggressiveness, but their role is poorly known.

METHODS

We evaluated the aggression-induced activation of NK1 neurons by double-labeling brain sections for NK1 receptors and c-Fos in two laboratory models of aggression. We also studied the effects of the NK1 antagonist L-703,606 in these models.

RESULTS

Aggressive encounters activated a large number of NK1 receptor-expressing neurons in areas relevant for aggression control. The activation was aggression-specific, because the effects of psychosocial encounters (that allowed sensory but not physical contacts) were markedly weaker. In the medial amygdala, the activation of neurons expressing NK1 receptors showed a marked positive correlation with the occurrence of violent attacks. In resident/intruder conflicts, NK1 blockade lowered the number of hard bites, without affecting milder forms of attack. In the model of violent aggression, attacks on vulnerable body parts of opponents (the main indicators of violence in this model) were decreased to the levels seen in control subjects. Autonomic deficits seen in the model of violent aggression were also ameliorated. The effects of the compound were not secondary to changes in locomotion or in the behavior of intruders.

CONCLUSIONS

Our data show that neurons expressing NK1 receptors are involved in the control of aggressiveness, especially in the expression of violent attacks. This suggests that NK1 antagonists-beyond anxiety and depression-might also be useful in the treatment of aggressiveness and violence.

A comparison of activation patterns of cells in selected prefrontal cortical and amygdala areas of rats which are more or less anxious in response to predator exposure or submersion stress

This study had two purposes. First: to compare predator and water submersion stress cFos activation in medial prefrontal cortices (mPFC) and the medial amygdala (MeA). Second: to identify markers of vulnerability to stressors within these areas. Rats were either predator or submersion stressed and tested 1.75 h later for anxiety. Immediately thereafter, rats were sacrificed and cFos expression was examined. Predator and submersion stress equally increased anxiety-like behavior in the elevated plus maze (EPM) and hole board. To examine vulnerability, rats which were less anxious (LA) and more (highly) anxious (MA) in the EPM were selected from among handled control and stressed animals. LA stressed rats were considered stress non-responsive while MA stressed rats were considered stress responsive. Predator stress, but not submersion stress, activated MeA cFos. CFos expression of mPFC cells was elevated in LA rats and reduced in MA rats in predator stressed animals only, correlating negatively with anxiety. These findings are consistent with data implicating greater mPFC excitability in protection against the effects on affect of traumatic stress. The findings also suggest that this conclusion is stressor specific, applying to predator stress but not submersion stress. Both stressors have been suggested to model hyperarousal and comorbid anxiety aspects of PTSD in humans. Hence the use of these paradigms to identify brain bases of vulnerability and resilience to traumatic stress in PTSD has translation potential. On the other hand, our evidence of stressor specificity of vulnerability/resilience markers raises a caution. The data suggest that preclinical markers of vulnerability/resilience in a given stress paradigm are at best suggestive, and translational value must ultimately be confirmed in humans.

Video teleconferencing with realistic simulation for medical education

This report describes how realistic patient simulation can be used with video teleconferencing to conduct long-distance clinical case discussions with realistic re-enactments of critical events. By observing what appears to be a real procedure unfolding in real time, it is intended that audience members will better learn and appreciate the lessons from conferences. A commercially available mannequin simulator and video teleconferencing technology were used in nine sessions between a free-standing simulation center and different conference sites throughout the U.S. Transmission was via high-speed telephone lines. In each conference, a clinical scenario was simulated on a screen. Audience members asked questions of a live simulated "patient" and family and later advised the care team on routine treatments and management of urgent clinical problems that arose during management of the mannequin simulator in a highly realistic clinical setting. Ninety-eight percent of respondents from one audience of 150 (response rate 60%) judged the quality of the presentation as "very good or excellent." In response to the statement that "the educational value of the presentation was much greater than that of a standard case conference," 95% scored 4 or 5 on a five-point Likert scale (where 5 is highest agreement). While all conferences were conducted successfully, there were instances of technical challenge in using teleconferencing technology. Technical information about the teleconferencing system and scenario preparation, contingency planning for failures, and other details of using this new teaching modality are described. Although audiences were enthusiastic in their response to this approach to clinical case conferences, further study is needed to assess the added value of interactive simulation for education compared to standard conference formats.

Suicidal Risk, Psychopathology, and Quality of Life in a Clinical Population of Adolescents

BACKGROUND

According to literature data, psychopathology is associated with both quality of life (QoL) and suicidal risk in adolescents, but the literature does not fully support a direct association between psychopathology and suicidal thoughts and behaviors. The aim of this study was to investigate the possible mediational role of QoL in the relationship between psychopathology and level of suicidal risk in a clinical sample of adolescents.

METHOD

The authors examined a clinical population of 134 adolescents, aged 13-18 years. Suicidal risk-having any current suicidal ideations and/or previous suicide attempt-was assessed by the Mini International Neuropsychiatric Interview. QoL was evaluated by the adolescent self-rated versions of "Das Intervertar zur Erfassung der Lebensqualität Kindern und Jugendlichen" (ILK: Measure of Quality of Life for Children and Adolescents) and psychopathology was measured by adolescent self-rated versions of the Strengths and Difficulties Questionnaire (SDQ). A mediational model, in which QoL mediated the relationship between psychopathology and suicidal risk controlling for gender and age, was tested by means of regression analyses.

RESULTS

Gender and age were both associated with suicidal risk. Self-reported QoL significantly mediated the relationships between emotional problems (=1.846; 95% BCa CI: 0.731-2.577), as well as peer problems (=0.883; 95% BCa CI: 0.055-1.561) and suicidal risk: more emotional and peer problems were associated with lower QoL, which in turn was related to higher level of suicidal risk.

CONCLUSION

Based on this study, which aims to make further steps in suicidal prevention, our findings suggest that clinicians should routinely screen the QoL of their patients, especially in adolescents with emotional and peer problems. Furthermore, it is important to focus intervention and treatment efforts on improving the QoL of adolescents with emotional and peer problems.

Activation patterns of cells in selected brain stem nuclei of more and less stress responsive rats in two animal models of PTSD - predator exposure and submersion stress

This study had two purposes. First: compare predator and water submersion stress cFos activation patterns in dorsal raphe (DR), locus coeruleus (LC) and periaqueductal gray (PAG). Second: identify markers of vulnerability to stressors within these areas. Rats were either predator or submersion stressed and tested 1.75 h later for anxiety-like behavior. Immediately thereafter, rats were sacrificed and cFos expression examined. In DR, serotonergic cells expressing or not expressing cFos were also counted. Predator and submersion stress increased anxiety-like behavior (in the elevated plus maze- EPM) equally over controls. Moreover, stressed rats spent equally less time in the center of the hole board than handled controls, another indication of increased anxiety-like behavior. To examine vulnerability, rats which were less anxious (LA) and more (highly) anxious (MA) in the EPM were selected from among handled control and stressed animals. LA rats in the stressed groups were considered stress non-responsive and MA stressed rats were considered stress responsive. LA and MA rats did not differ in cFos expression in any brain area, though stressors did increase cFos cell counts in all areas over controls. Intriguingly, the number of serotonergic DR neurons not activated by stress predicted degree of anxiety response to submersion stress only. LA submersion stressed rats had more serotonergic cells than all other groups, and MA submersion stressed rats had fewer serotonergic cells than all other groups, which did not differ. Moreover, these cell counts correlated with EPM anxiety. We conclude that a surplus of such cells protects against anxiogenic effects of submersion, while a paucity of such cells enhances vulnerability to submersion stress. Other data suggest serotonergic cells may exert their effects via inhibition of dorsolateral PAG cells during submersion stress. Findings are discussed with respect to serotonergic transmission in vulnerability to predator stress and relevance of findings for post traumatic stress disorder (PTSD). This article is part of a Special Issue entitled 'Post-Traumatic Stress Disorder'.

Reactive and proactive aggression in clinical adolescents with attention-deficit/hyperactivity disorder: The moderating role of gender and comorbidities

Aggression is well-known problem in adolescent with Attention-Deficit/Hyperactivity Disorder (ADHD), but the precise relation of reactive and proactive aggression by gender and comorbidities has not been characterized in this population. The aim of this study was to assess the level of reactive and proactive aggression in adolescents with ADHD and in matched non-ADHD clinical controls. The level of aggression was assessed by the Reactive and Proactive Aggression Questionnaire in 391 adolescents with ADHD and in 391 matched non-ADHD clinical controls. The selection of adolescents with ADHD was representative for a three-year-long period in Vadaskert Child Psychiatry Hospital. General Linear Model was used to assess the difference by ADHD, gender, and comorbidities on the level of reactive and proactive aggression. The presence of ADHD was associated with higher levels of reactive and proactive aggression. In girls, the effect of ADHD on reactive aggression was more profound. The presence of oppositional defiant disorder or conduct disorder in both groups resulted in higher levels of aggression. Our data suggest that adolescents with ADHD have higher level of aggressive behavior, and girls are especially vulnerable in terms of reactive aggressive behavior.

Potential salivary biomarkers and their genetic effects in a pilot study of adolescent boys with externalizing problems

AIMS

Beside the well-known stress response marker cortisol, salivary alpha-amylase is receiving increasing attention. Numerous studies have investigated the potential biomarker properties of cortisol mirroring abnormal hypothalamic-pituitary-adrenal axis activity in connection to both internalizing and externalizing behavior problems. The other major physiological system involved in stress reactivity, the sympathetic nervous system activity can be also measured by the surrogate marker of salivary alpha-amylase. Most of the studies applied a stressful situation to obtain inter-individual differences in stress-reactivity, although differences in the baseline level of cortisol have been also shown in relation to externalizing problems. To test the relevance of another (easier) biomarker, we selected to study baseline circadian salivary cortisol and alpha-amylase levels among adolescent boys with externalizing problems.

METHODS

Saliva samples were collected at 3 time-points (morning, noon, evening) during 3 consecutive days from 37 inpatient boys (mean age 12.4±1.0). Cortisol and alpha-amylase levels were measured by enzyme-linked immunosorbent and kinetic enzyme assays, respectively. Genetic variants in the hypothalamic-pituitary-adrenal axis and the norepinephrine transporter or catecholamine metabolizing enzymes were tested for potential moderating effects at these salivary biomarkers.

RESULTS

Saliva cortisol showed the classical diurnal fluctuation in boys with externalizing problems (possibly from a lower morning level), but it was not modified by the presence of either conduct, oppositional defiant or attention-deficit/hyperactivity disorder. The diurnal fluctuation of the salivary alpha-amylase levels was also typical, but the presence of conduct disorder was associated with significantly lower alpha-amylase activity (p=0.024) among boys with externalizing problems. The catechol-O-methyltransferase Val158Met (rs4680) polymorphism had an additional effect on salivary alpha-amylase: boys with homozygote genotypes had lower alpha-amylase activity at all 3 time-points compared to Val/Met heterozygotes (p=0.045).

CONCLUSIONS

Our preliminary data suggest that salivary alpha-amylase might be used to further characterize subgroups within externalizing problems, however, this biomarker might be modified by certain genetic polymorphisms.

Post-weaning social isolation in male mice leads to abnormal aggression and disrupted network organization in the prefrontal cortex: Contribution of parvalbumin interneurons with or without perineuronal nets

Adverse social experiences during childhood increase the risk of developing aggression-related psychopathologies. The prefrontal cortex (PFC) is a key regulator of social behavior, where experience-dependent network development is tied to the maturation of parvalbumin-positive (PV+) interneurons. Maltreatment in childhood could impact PFC development and lead to disturbances in social behavior during later life. However, our knowledge regarding the impact of early-life social stress on PFC operation and PV+ cell function is still scarce. Here, we used post-weaning social isolation (PWSI) to model early-life social neglect in mice and to study the associated neuronal changes in the PFC, additionally distinguishing between the two main subpopulations of PV+ interneurons, i.e. those without or those enwrapped by perineuronal nets (PNN). For the first time to such detailed extent in mice, we show that PWSI induced disturbances in social behavior, including abnormal aggression, excessive vigilance and fragmented behavioral organization. PWSI mice showed altered resting-state and fighting-induced co-activation patterns between orbitofrontal and medial PFC (mPFC) subregions, with a particularly highly elevated activity in the mPFC. Surprisingly, aggressive interaction was associated with a higher recruitment of mPFC PV+ neurons that were surrounded by PNN in PWSI mice that seemed to mediate the emergence of social deficits. PWSI did not affect the number of PV+ neurons and PNN density, but enhanced PV and PNN intensity as well as cortical and subcortical glutamatergic drive onto mPFC PV+ neurons. Our results suggest that the increased excitatory input of PV+ cells could emerge as a compensatory mechanism for the PV+ neuron-mediated impaired inhibition of mPFC layer 5 pyramidal neurons, since we found lower numbers of GABAergic PV+ puncta on the perisomatic region of these cells. In conclusion, PWSI leads to altered PV-PNN activity and impaired excitatory/inhibitory balance in the mPFC, which possibly contributes to social behavioral disruptions seen in PWSI mice. Our data advances our understanding on how early-life social stress can impact the maturing PFC and lead to the development of social abnormalities in adulthood.