Meeting Abstract
Public information was recently found to influence the physiological and behavioral response to food reduction in songbirds: red crossbills (Loxia curvirostra) that were food reduced for several days did not have significant elevations in circulating baseline corticosterone (CORT) or activity levels unless their neighbors were also food reduced. Physiological and behavioral responses to glucocorticoids are, however, enacted through receptors that may be expressed differentially in target tissues. We investigated the influence of public information on the expression of the high-affinity mineralocorticoid receptor (MR) and low-affinity glucocorticoid receptor (GR) mRNA in captive red crossbills. Given the role of MR in negative feedback mechanisms on basal CORT secretion, we predicted public information from food-restricted individuals would reduce MR expression in brain regions known to regulate hypothalamic-pituitary-adrenal activity – thereby allowing increased or sustained HPA-activity during subsequent stressors. Such a mechanism may explain why food reduced crossbills paired with food reduced neighbors show higher CORT secretion than those paired with well-fed neighbors. Our results supported our predictions in regards to MR: MR expression in hippocampus was lower in birds with food-reduced neighbors. Interestingly, food reduction itself appeared to have no influence on MR or GR expression.
