Can laboratory animals violate behavioural norms? Towards a preclinical model of conduct disorder

Caring animals and the ways we wrong them

Many nonhuman animals have the emotional capacities to form caring relationships that matter to them, and for their immediate welfare. Drawing from care ethics, we argue that these relationships also matter as objectively valuable states of affairs. They are part of what is good in this world. However, the value of care is precarious in human-animal interactions. Be it in farming, research, wildlife 'management', zoos, or pet-keeping, the prevention, disruption, manipulation, and instrumentalization of care in animals by humans is ubiquitous. We criticize a narrow conception of welfare that, in practice, tends to overlook non-experiential forms of harm that occur when we interfere with caring animals. Additionally, we point out wrongs against caring animals that are not just unaccounted for but denied by even an expansive welfare perspective: The instrumentalization of care and caring animals in systems of use can occur as a harmless wrong that an approach purely focused on welfare may, in fact, condone. We should therefore adopt an ethical perspective that goes beyond welfare in our dealings with caring animals.

Callous unemotional trait-like mice and their stressed dams

The co-occurrence of excess rates of aggression, general violation of societal norms and callous-unemotional trait confers specific risk for adult psychopathy. With the aim to address experimentally a model of conduct disorder, we investigated the male offspring of individual mouse dams characterized by high basal plasma corticosterone concentration (HC trait). Notably, classification indices correlated selectively in these females with quite poor maternal care devoted to their offspring. Contrary to their HC mothers, adult male offspring exhibited an integrated profile of dampened physiological reactivity to external stressors co-occurring poor sociability/emotional contagion, impaired punishment-induced memory, and exacerbated aggression. A significant reduction of glucocorticoid and opioid mu receptors' expression in frontal cortex of model HC offspring was also evidenced. Moreover, in the absence of changes in oxytocin receptor in behaviorally-relevant neural areas, we showed that intranasal oxytocin administration (0 or 20.0 µg/kg) selectively modulated specific components of the behavioral phenotype. Ultimately, current data support the notion that maternally-inoculated environmental stress early in development may represent a critical risk factor in disturbances characterised by abnormal aggression and excess callousness.

Role of Callous and Unemotional (CU) Traits on the Development of Youth with Behavioral Disorders: A Systematic Review

Numerous studies have shown that youth with behavioral disorders (BD) present an increased risk for developing severe and persistent antisocial behaviors in adulthood. Retrospective research notes that not all children and adolescents follow a negative trajectory and explains this heterogeneity in particular by the severity of CU traits. Our study examines how these traits affect the functioning of children and adolescents with BD. Method: A systematic literature review conducted through various databases and using different keywords made it possible to analyze 52 studies published from 2015 to 2020 that measured the bidirectional effects of CU traits on the functioning of young. Results: Out of the 52 studies, 47 analyzed links between CU traits and neurobiological or mental health, 20 examined family and school contexts, eight focused on social adjustment, 10 on social interactions and 19 measured links with cognitive functioning, especially executive functions. Conclusion: Consistent with previous recommendations in the field, our findings emphasize the importance of assessing the presence of UC traits in early childhood to prevent the emergence of comorbid disorders and to target multimodal (early) interventions to influence the life trajectories of youth with high CU traits.

Methylphenidate administration promotes sociability and reduces aggression in a mouse model of callousness

RATIONALE

Deficits in empathy constitute a distinctive feature of several psychopathologies, including conduct disorder (CD). The co-occurrence of callous-unemotional (CU) traits, excess rates of aggression and violation of societal norms confers specific risk for adult psychopathy. To date, the off-label use of methylphenidate (MPH) constitutes the drug treatment of choice.

OBJECTIVES

Herein, we tested the therapeutic potential of MPH in a recently devised mouse model recapitulating the core phenotypic abnormalities of CD.

METHODS

Two subgroups of BALB/cJ male mice exhibiting opposite profiles of emotional contagion (i.e. socially transmitted adoption of another's emotional states) were investigated for reactive aggression, sociability, attention control, anxiety-related behaviours and locomotor activity, in response to MPH administration (0.0, 3.0 or 6.0 mg/kg).

RESULTS

Our data indicate that mice selected for excess callousness exhibit phenotypic abnormalities isomorphic to the symptoms of CD: stability of the low emotional contagion trait, increased aggression and reduced sociability. In accordance with our predictions, MPH reduced aggression and increased sociability in callous mice; yet, it failed to restore the low responsiveness to the emotions of a conspecific in pain, isomorphic to CU traits.

CONCLUSIONS

Although our data support the notion that MPH may contribute to the management of excess aggression in CD patients, additional studies shall identify specific treatments to target the callousness domain. The latter, unaffected by MPH in our experimental model, demands focused consideration whereby it constitutes a specifier associated with a worse prognosis.

Low empathy-like behaviour in male mice associates with impaired sociability, emotional memory, physiological stress reactivity and variations in neurobiological regulations

Deficits in empathy have been proposed to constitute a hallmark of several psychiatric disturbances like conduct disorder, antisocial and narcissistic personality disorders. Limited sensitivity to punishment, shallow or deficient affect and reduced physiological reactivity to environmental stressors have been often reported to co-occur with limited empathy and contribute to the onset of antisocial phenotypes. Empathy in its simplest form (i.e. emotional contagion) is addressed in preclinical models through the evaluation of the social transmission of emotional states: mice exposed to a painful stimulus display a higher response if in the presence of a familiar individual experiencing a higher degree of discomfort, than in isolation. In the present study, we investigated whether a reduction of emotional contagion can be considered a predictor of reduced sociality, sensitivity to punishment and physiological stress reactivity. To this aim, we first evaluated emotional contagion in a group of Balb/cJ mice and then discretised their values in four quartiles. The upper (i.e. Emotional Contagion Prone, ECP) and the lower (i.e. Emotional Contagion Resistant, ECR) quartiles constituted the experimental groups. Our results indicate that mice in the lower quartile are characterized by reduced sociability, impaired memory of negative events and dampened hypothalamic-pituitary-adrenocortical reactivity to external stressors. Furthermore, in the absence of changes in oxytocin receptor density, we show that these mice exhibit elevated concentrations of oxytocin and vasopressin and reduced density of BDNF receptors in behaviourally-relevant brain areas. Thus, not only do present results translate to the preclinical investigation of psychiatric disturbances, but also they can contribute to the study of emotional contagion in terms of its adaptive significance.