Effets comportementaux et cognitifs de la phencyclidine (PCP) chez le rat

L'administration répétée de phencyclidine (PCP) permet de modéliser les symptômes positifs et négatifs de la schizophrénie chez l'animal. Des études récentes démontrent que l'injection sous-chronique de PCP chez le rat entraîne l'apparition de déficits cognitifs communément attribués à une dysfonction frontale, ainsi qu'une diminution de l'utilisation de la dopamine dans le cortex préfrontal possiblement associée à une hyperactivité dopaminergique sous-corticale (Jentsch et al., 1997b). La présente étude se propose d'examiner le patron des fonctions intactes et déficitaires chez le modèle animal PCP dans des situations faisant appel à la mémoire, la coordination motrice, les comportements ambulatoires, la néophobie environnementale et alimentaire, ainsi qu'à l'organisation de séquences motrices. Les résultats obtenus indiquent qu'une administration de PCP pendant 15 jours chez le rat provoque une altération de la mémoire de référence, une perturbation de la mémoire de travail dans le labyrinthe radial mais pas dans le labyrinthe en T, et une difficulté à organiser des séquences motrices lors du toilettage

Mindfulness and psychoeducation to manage stress in amnestic mild cognitive impairment : a pilot study

Objectives: Amnestic mild cognitive impairment (aMCI) often corresponds to the prodromal stage of Alzheimer disease (AD). The aMCI stage represents a crucial time window to apply preventive interventions in an attempt to delay cognitive decline. Stress, one of AD’s modifiable risk factors frequently co-occurring with aMCI, stands out as a key intervention target. The goal of this study was to assess the impacts of two nonpharmacological interventions, mindfulness and psychoeducation, on stress at the psychological and physiological levels among aMCI older adults. Methods: Forty-eight aMCI participants were randomized between a mindfulness-based intervention (MBI) and a psychoeducation-based intervention (PBI) for eight weekly sessions. Anxiety symptoms, perceived stress levels, cortisol awakening response (CAR), and coping strategies were assessed pre- and post-intervention. Mindfulness attitudes and time dedicated to at-home meditative practices were evaluated in the MBI group. Results: The main results revealed a slight reduction of the CAR among MBI participants who practiced meditation at home the most and a decrease in perceived stress levels in the PBI group. Both interventions enhanced problem-focused coping strategies. Conclusion: In sum, this pilot study supports the potential of MBI and PBI to reduce stress at the physiological and psychological level, respectively, and increase coping strategies in older adults at risk for AD

Interplay between pro-inflammatory cytokines and growth factors in depressive illnesses

The development of depressive disorders had long been attributed to monoamine variations, and pharmacological treatment strategies likewise focused on methods of altering monoamine availability. However, the limited success achieved by treatments that altered these processes spurred the search for alternative mechanisms and treatments. Here we provide a brief overview concerning a possible role for pro-inflammatory cytokines and growth factors in major depression, as well as the possibility of targeting these factors in treating this disorder. The data suggest that focusing on one or another cytokine or growth factor might be counterproductive, especially as these factors may act sequentially or in parallel in affecting depressive disorders. It is also suggested that cytokines and growth factors might be useful biomarkers for individualized treatments of depressive illnesses

Effects of a mindfulness-based intervention on circulating cytokine levels in individuals with amnestic mild cognitive impairment : a pilot study

Peripheral inflammation plays an important role in the pathophysiology of Alzheimer’s disease (AD) and dysregulations in circulating levels of different inflammatory mediators are detectable as early as the mild cognitive impairment (MCI) stage towards AD. Depressive symptoms, another risk factor of AD, are often found in individuals with MCI and associated with heightened levels of peripheral inflammatory mediators. Diminution in depressive symptoms and alterations of peripheral inflammation profiles have been observed following Mindfulness-based interventions (MBIs). In this pilot randomized-control trial, the impact of a mindfulness-based intervention (MBI) was compared to that of a psychoeducation-based intervention (PBI) on the peripheral inflammation profile and depressive symptomatology of participants with MCI. Plasma samples and scores on the Geriatric Depression scale (GDS) were obtained from 12 participants per group before and after the 8-week interventions. Flow cytometry allowed for inter-group comparisons of the pro-inflammatory cytokines Interleukin (IL)-6 and Tumor Necrosis Factor (TNF)-α levels. Post-MBI, two tendencies stand out regarding inflammation profiles: 1) a decrease of TNF-α for participants having higher initial levels of this cytokine, and 2) an increase of IL-6 levels for all participants. In the PBI group, the cytokine levels remained unchanged post-intervention. Regarding depressive symptomatology, no significant variations were noted for both groups. Moreover, variations on depressive symptoms and peripheral levels of cytokines were not correlated. MBI could exert a physiological effect on an important feature of AD, namely inflammation. Furthermore, action mechanisms behind physiological and psychological effects of MBIs could stem from independent sources. This remains to be demonstrated with more robust data

Scoping study of definitions and instruments measuring vulnerability in older adults

Abstract: It is important to foster social participation and health equity especially for older adults in situations of vulnerability Despite growing interest in the concept of vulnerability there is no consensus regarding how to define or measure it This paper provides an inventory and synthesis of definitions and instruments measuring vulnerability in older adults Using a scoping study framework eight databases Abstracts in Social Gerontology Academic Search Complete AgeLine CINAHL MEDLINE SocINDEX PsycInfo Scopus were searched with relevant keywords Vulnerab AND Concept Defin Meaning Terminology Measurement Assessment Indicator Instrument Scale Questionnaire OR Test AND Aging Ageing Elder Gerontolog Older OR Senior Thirty-one original definitions and five measurement instruments were identified content-analyzed and compared Vulnerability definitions mostly focused on people under conditions that increased their risk of being harmed because of individual physical factors or the social environment Considering these definitions experts in the field of aging including two representing older adults took part in a workshop and a consensus was reached to define a situation of vulnerability as a set of circumstances in which one or more individuals experience at a specific moment in time one or multiple physiological psychological socioeconomic or social difficulties that may interact to increase their risk of being harmed or having coping problems that lead to negative consequences on their life Although none of the measures fully targeted this definition the Perceived Vulnerability Scale PVS was judged best at operationalizing the concept with 22 items considering feelings of vulnerability toward personal and environmental factors it also has good psychometric properties The proposed definition and the PVS help to provide a common language and measure in health and social sciences research policy and practice identifying and reaching older adults in situations of vulnerability and intervening to foster social participation and health equity

Behavior and pro-inflammatory cytokine variations among submissive and dominant mice engaged in aggressive encounters: Moderation by corticosterone reactivity

Psychosocial stressors contribute to the pathophysiology of affective disorders and variations of cytokine functioning have been implicated in this process. The present investigation demonstrated, in mice, the impact of stressful aggressive encounters on activity levels, plasma corticosterone and cytokine concentrations, and on cytokine mRNA expression within the prefrontal cortex (PFC) and hippocampus. As glucocorticoids have been tied to cytokine variations, mice were subdivided into low or high corticosterone responders, defined in terms of circulating hormone levels 75 min post-confrontation. Interestingly, stressor-induced effects among low and high responders varied as a function of whether mice were submissive or dominant during the aggressive bout. Agonistic encounters elicited subsequent hyperactivity, particularly among low corticosterone responders and among dominant mice. Plasma levels of corticosterone and interleukin (IL)-6 concomitantly increased after aggressive encounters and varied with dominance status and with the low versus high corticosterone response. Among the low responders corticosterone and IL-6 increases were modest and only apparent among submissive mice, whereas among high responders these elevations were more pronounced and comparable in submissive and dominant mice. Aggressive episodes also increased IL-1β and IL-6 mRNA brain expression. The IL-1β rise was greater in the PFC and hippocampus of submissive mice that were low responders. Among high responders IL-1β and IL-6 increased in both groups, although in the PFC this effect was specific to dominant mice. The data are discussed in terms of their relevance to the impact of aggressive encounters on affective behaviors, and to the role that cytokines might play in this regard

Palatable Food Dampens the Long-Term Behavioral and Endocrine Effects of Juvenile Stressor Exposure but May Also Provoke Metabolic Syndrome in Rats

The juvenile period is marked by a reorganization and growth of important brain regions including structures associating with reward seeking behaviors such as the nucleus accumbens (NA) and prefrontal cortex (PFC). These changes are impacted by stressors during the juvenile period and may lead to a predisposition to stress induced psychopathology and abnormal development of brain reward systems. Like in humans, adult rodents engage certain coping mechanisms such as increases in the consumption of calorie-rich palatable foods to reduce stress, but this behavior can lead to obesity and metabolic disorders. In this study, we examined whether stressors during the juvenile period led to increased caloric intake when a palatable diet was accessible, and whether this diet attenuated adult stress responses. In addition, we examined if the stress buffering effects produced by the palatable diet were also accompanied by an offset propensity towards obesity, and by alterations in mRNA expression of dopamine (DA) receptors in the NA and PFC in adulthood. To this end, juvenile male Wistar rats underwent episodic stressor exposure (forced swim, elevated platform stress and restraint) on postnatal days (PD) 27-29 and received access to regular chow or daily limited access to a palatable diet until adulthood. At the age of 2 months, rats were tested on a social interaction test that screens for anxiety-like behaviors and their endocrine responses to an acute stressor. Animals were sacrificed, and their brains processed to detect differences in DA receptor subtype expression in the PFC and NA using qPCR. Results showed that rats that were stressed during the juvenile period displayed higher social anxiety and a sensitized corticosterone response as adults and these effects were attenuated by access to the palatable diet. Nevertheless, rats that experienced juvenile stress and consumed a palatable diet showed greater adiposity in adulthood. Interestingly, the same group displayed greater mRNA expression of DA receptors at the NA. This suggests that access to a palatable diet mitigates the behavioral and endocrine effects of juvenile stressor exposure in adulthood, but at the cost of metabolic imbalances and a sensitized dopaminergic system

The differential impact of social defeat on mice living in isolation or groups in an enriched environment: Plasma corticosterone and monoamine variations

Social defeat in mice is a potent stressor that promotes the development of depressive- and anxiety-like behaviours, as well as variations of neuroendocrine and brain neurotransmitter activity. Although environmental enrichment may protect against some of the adverse behavioural and biological effects of social defeat, it seems that, among male group-housed mice maintained in an enriched environment (EE), aggressive behaviours may be more readily instigated, thus promoting distress and exacerbating psychopathological features. Thus, although an EE can potentially have numerous beneficial effects, these may depend on the general conditions in which mice were raised. It was observed in the current investigations that EE group-housed BALB/cByJ mice displayed increased anxiety-like behaviours compared to their counterparts maintained in a standard environment (SE). Furthermore, in response to social defeat, EE group-housed male mice exhibited decreased weight gain, exaggerated corticosterone elevations and altered hippocampal norepinephrine utilization compared to their SE counterparts. These effects were not apparent in the individually housed EE mice and, in fact, enrichment among these mice appeared to buffer against serotonin changes induced by social defeat. It is possible that some potentially beneficial effects of enrichment were precluded among group-housed mice, possibly owing to social disturbances that might occur in these conditions. In fact, even if social interaction is an essential feature of enrichment, it seems that some of the positive effects of this housing condition might be optimal when mice are housed individually, particularly with regard to buffering the effects of social defeat

Post-weaning environmental enrichment in male CD-1 mice: Impact on social behaviors, corticosterone levels and prefrontal cytokine expression in adulthood

Environmental enrichment is typically associated with enhanced well-being, improved cognitive function and stress resilience. However, in some instances grouping adult male mice in enriched conditions promoted a stressful environment, which resulted in elevated endocrine, monoamine and inflammatory outcomes in response to subsequent stressor exposure. The current investigation examined whether raising male mice in an enriched environment (EE) would modulate social and anxiety-like behaviors in early adulthood and i