Effects of reproductive status on behavioral and endocrine responses to acute stress in a biparental rodent, the California mouse (Peromyscus californicus)

Abstract

In several mammalian species, lactating females show blunted neural, hormonal, and behavioral responses to stressors. It is not known whether new fathers also show stress hyporesponsiveness in species in which males provide infant care. To test this possibility, we determined the effects of male and female reproductive status on stress responsiveness in the biparental, monogamous California mouse (Peromyscus californicus).Breeding (N=8 females, 8 males), nonbreeding (N=10 females, 10 males) and virgin mice (N=12 females, 9 males) were exposed to a 5-min predator-urine stressor at two time points, corresponding to the early postpartum (5–7 days postpartum) and mid/late postpartum (19–21 days postpartum) phases, and blood samples were collected immediately afterwards. Baseline blood samples were obtained 2 days prior to each stress test. Baseline plasma corticosterone (CORT) concentrations did not differ among male or female groups. CORT responses to the stressor did not differ among female reproductive groups, and all three groups showed distinct behavioral responses to predator urine. Virgin males tended to increase their CORT response from the first to the second stress test, while breeding and nonbreeding males did not. Moreover, virgin and nonbreeding males showed significant behavioral changes in response to predator urine, whereas breeding males did not. These results suggest that adrenocortical responses to a repeated stressor in male California mice may be modulated by cohabitation with a female, whereas behavioral responses to stress may be blunted by parental status.

Defensive responses of Brandt's voles (Lasiopodomys brandtii) to chronic predatory stress

“…ACTH is a hormone produced and secreted by the anterior pituitary gland in response to various stressors, including predation risk [10]. Circulating ACTH is the key regulator of corticosterone secretion by the adrenal cortex [21].…”

Glucocorticoids, Aerobic Physiology, and Locomotor Behavior in California Mice

“…While we have not explicitly tested CORT repeatability in P. californicus, previous data show consistent circadian rhythmicity in CORT levels . Specifically, within our colony of mice, pooled data from two previous studies (Chauke et al 2011;Harris et al 2011) indicate that CORT AM values are repeatable within individuals ( , r p 0.356 P p ,…”

“…Plasma samples were assayed for CORT with a commercially available kit (double-antibody corticosterone radioimmunoassay, 07-120102, MP Biomedicals, Costa Mesa, CA) that had been fully validated for use with California mouse plasma (Chauke et al 2011). Plasma samples were diluted either 1 : 400 or 1 : 800, depending on the expected concentration of hormone in the sample (higher values were expected at the 1800-hours time point); samples were assayed in duplicate.…”

Individual Variation in Paternal Responses of Virgin Male California Mice (Peromyscus californicus): Behavioral and Physiological Correlates

“…Assay sensitivity at 90% binding was 0.9 pg, and inter-and intra-assay coefficients of variation (CVs) were 15.5% and 3.9%, respectively ( assays). N p 54 Plasma concentrations of corticosterone were determined at UCR as described previously (Chauke et al 2011). Briefly, samples were analyzed in duplicate using an 125 I double-antibody radioimmunoassay kit (07120102, MP Biomedicals, Costa Mesa, CA) that our lab has validated for P. californicus plasma using standard biochemical and biological validation procedures (Chauke et al 2011;M.…”