Effects of social context on endocrine function and Zif268 expression in response to an acute stressor in adolescent and adult rats

Abstract

There is a paucity of studies comparing social buffering in adolescents and adults, despite their marked differences in social behavior. We investigated whether greater effects of social buffering on plasma corticosterone concentrations and expression of Zif268 in neural regions after an acute stressor would be found in adolescent than adult rats. Samples were obtained before and after 1h of isolation stress and after either 1 or 3h of recovery back in the colony with either a familiar or unfamiliar cage partner. Adolescent and adult rats did not differ in plasma concentrations of corticosterone at any time point. Corticosterone concentrations were higher after 1h isolation than at baseline (p<0.001), and rats with a familiar partner during the recovery phase had lower corticosterone concentrations than did rats with an unfamiliar partner (p=0.02). Zif268 immunoreactive cell counts were higher in the arcuate nucleus in both age groups after isolation (p=0.007) and in the paraventricular nucleus of adolescents than adults during the recovery phase irrespective of partner familiarity. There was a significant decrease in immunoreactive cell counts after 1h isolation compared to baseline in the basolateral amygdala, central nucleus of the amygdala, and in the pyramidal layer of the hippocampus (all p<0.05). An effect of partner familiarity on Zif268 immunoreactive cell counts was found in the granule layer of the dentate gyrus irrespective of age (higher in those with a familiar partner, p=0.03) and in the medial prefrontal cortex in adolescents (higher with an unfamiliar partner, p=0.02). Overall, the acute stress and partner familiarity produced a similar pattern of results in adolescents and adults, with both age groups sensitive to the social context.

Effects of sex and housing on social, spatial, and motor behavior in adult rats exposed to moderate levels of alcohol during prenatal development

“…For example, the contrast between negative effects of paired-housing on ethanol-exposed and control rats in the present study and some positive effects of housing ethanol-exposed rats in triads with two control animals observed by Middleton et al [51] suggests that the number of cage-mates may be a critical factor that should be explored in future studies. A number of studies have demonstrated that the presence of other rats can have a positive influence on physiological and behavioral responses to distress—a behavioral phenomenon known as social buffering [28, 32, 33, 56, 68, 69]. The present data suggest that adult PAE male rats do not benefit from social housing, however, whether PAE negatively impacts social buffering early in development and/or whether these acute manipulations of the social environment persist into adulthood has not been examined.…”

Adolescence and the ontogeny of the hormonal stress response in male and female rats and mice

“…For instance, brief exposures to a novel environment (Goldman et al, 1973) or social isolation (Hodges et al, 2014) result in similar corticosterone responses in pre-, mid- and post-adolescent rats. Furthermore, some stressors, such as exposure to lipopolysaccharide (Girard-Joyal et al, 2015; Goble et al, 2011) or placement in the open arm of an elevated plus maze (McCormick et al, 2008) evoke lesser ACTH and/or corticosterone secretion in pre- and mid-adolescent male rats and female mice compared to adults (Figure 3).…”

Social buffering in a bird

“…Terranova, Cirulli, & Laviola, 1999;Varlinskaya, 2013) the stressor and those that focus on stress alleviation through social housing prior to and/or following (e.g. Hodges, Green, Simone, & McCormick, 2014;McCormick, Merrick, Secen, & Helmreich, 2007) the stressor (Kiyokawa, Takeuchi, & Mori, 2007). The vast majority of social-buffering studies have focused on mammals and many parameters have been used to measure social buffering.…”

“…These include traditional stress indicators such as activation of the hypothalamic-pituitary-adrenal axis (e.g. increased heart rate, cortisol; Hodges et al, 2014) and behavioural responses (e.g. escape attempts, Gonzalez et al, 2013), through to neural responses (e.g.…”

“…However, many studies purporting to measure social-buffering effects have used social isolation itself as the stressor (e.g. Hodges et al, 2014;Hostetler & Ryabinin, 2014;. In this latter case changes in behaviour or physiology are likely to reflect a general return to baseline following separation, rather than a social-buffering effect.…”