Risk assessment behaviors associated with corticosterone trigger the defense reaction to social isolation in rats: Role of the anterior cingulate cortex

Abstract

The extent to which the hypothalamic-pituitary-adrenal axis is activated by short-term and long-term consequences of stress is still open to investigation. This study aimed to determine (i) the correlation between plasma corticosterone and exploratory behavior exhibited by rats subjected to the elevated plus maze (EPM) following different periods of social isolation, (ii) the effects of the corticosterone synthesis blocker, metyrapone, on the behavioral consequences of isolation, and (iii) whether corticosterone produces its effects through an action on the anterior cingulate cortex, area 1 (Cg1). Rats were subjected to 30-min, 2-h, 24-h, or 7-day isolation periods before EPM exposure and plasma corticosterone assessments. Isolation for longer periods of time produced greater anxiogenic-like effects on the EPM. However, stretched attend posture (SAP) and plasma corticosterone concentrations were increased significantly after 30 min of isolation. Among all of the behavioral categories measured in the EPM, only SAP positively correlated with plasma corticosterone. Metyrapone injected prior to the 24 h isolation period reversed the anxiogenic effects of isolation. Moreover, corticosterone injected into the Cg1 produced a selective increase in SAP. These findings indicate that risk assessment behavior induced by the action of corticosterone on Cg1 neurons initiates a cascade of defensive responses during exposure to stressors.

Early Life Stress Increases Metabolic Risk, HPA Axis Reactivity, and Depressive-Like Behavior When Combined with Postweaning Social Isolation in Rats

“…ELS has been observed to induce long-term alterations in an age-dependent manner, suggesting that the dissimilarities between our results and those previously described could be attributed to a differential effect of MS180 on adolescent and adult offspring. Although reports of the effects of social isolation on CORT levels differ [59–62], numerous studies indicate that this stressor causes an increase in the basal CORT of both males and females [63–66]. Moreover, consistent with our findings, MS180 has been observed to show increased HPA axis reactivity when combined with an unpredictable chronic stressor [67].…”

Effects of intra-infralimbic prefrontal cortex injections of cannabidiol in the modulation of emotional behaviors in rats: Contribution of 5HT1A receptors and stressful experiences

“…Even if exposure to the EPM increases plasma corticosterone concentrations [78,79], there is a component of controllable stress in this model since the animal can avoid the open, more aversive arms. The concept of stress control is based on the capacity of the animal to manipulate the intensity, termination, duration, pattern or the onset of a given stressor [80].…”

Rats with differential self-grooming expression in the elevated plus-maze do not differ in anxiety-related behaviors

“…Our results did not indicate any clear relation between basal monoamines or corticosterone concentrations and grooming response in the EPM. Since exposure of rats to a novel environment like the EPM induces grooming behavior (as demonstrated here) and also increases plasma corticosterone [57] and monoamines in diverse brain areas [58], it was reasonable to cogitate a relation between these phenomena. Few studies, however, explored the relationship between stress hormones, specially corticosterone, and self-grooming response.…”