Abstract
Experiencing stress during adolescence can increase neophobic behaviors in adulthood, but most tests have been conducted in the absence of conspecifics. Conspecifics can modulate responses to stressors, for example by acting as ‘social buffers’ to attenuate the aversive appraisal of stressors. Here, we investigate the long-term effects of adolescent stress on the behavioral responses to novel stimuli (a mild stressor) across social contexts in an affiliative passerine bird, the zebra finch. During early (days 40–60) or late (days 65–85) adolescence the birds (n=66) were dosed with either saline or the hormone corticosterone (CORT). CORT was given in order to mimic a physiological stress response and saline was given as a control. In adulthood, the birds' behavioral responses to a novel environment were recorded in both the presence and absence of conspecifics. An acute CORT response was also quantified in adolescence and adulthood. Our findings show clear evidence of social context mediating any long-term effects of adolescent stress. In the presence of familiar conspecifics no treatment effects were detected. Individually, birds dosed with CORT in early adolescence were slower to enter a novel environment, spent more time perching in the same novel environment, and, if female, engaged in more risk assessment. Birds dosed in late adolescence were unaffected. No treatment effects were detected on CORT, but adolescents had a higher CORT concentration than adults. Our results are the first to suggest that familiar conspecifics in adulthood can buffer the long-term effects of stress that occurred during early adolescence.
Highlights
Stimuli that are perceived as a threat activate the hypothalamic-pituitary-adrenal axis, a neuroendocrine cascade regulating the secretion of glucocorticoids (GCs), such as corticosterone (CORT) in rodents and birds (Romero, 2004; Sapolsky et al, 2000)
CORT likely has sustained effects on adult stress responses by altering neural expression of GC receptors, subsequently heightening the concentration of CORT secreted in response to stressors and in turn heightening the expression of neophobic behavior (Banerjee et al, 2012; Isgor et al, 2004; Zimmer and Spencer, 2014)
Latency to enter the novel environment was affected by CORT in the individual context (F3,58 = 7.66, p ≤ 0.001; Fig. 2a), but not the group context (F3,14.30 = 0.03, p = 0.994; Fig. 2b)
Summary
Stimuli that are perceived as a (potential) threat activate the hypothalamic-pituitary-adrenal axis, a neuroendocrine cascade regulating the secretion of glucocorticoids (GCs), such as corticosterone (CORT) in rodents and birds (Romero, 2004; Sapolsky et al, 2000). Exposure to stressors during early post-natal development can have sustained effects on an adult's stress response (Sachser et al, 2011; Lupien et al, 2009; Monaghan, 2008), with adult neophobic behaviors and stressor-induced CORT concentration higher in those animals exposed to developmental stress compared to control animals (Hollis et al, 2013). CORT likely has sustained effects on adult stress responses by altering neural expression of GC receptors, subsequently heightening the concentration of CORT secreted in response to stressors and in turn heightening the expression of neophobic behavior (Banerjee et al, 2012; Isgor et al, 2004; Zimmer and Spencer, 2014)
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