Prior parental experience attenuates hormonal stress responses and alters hippocampal glucocorticoid receptors in biparental rock doves

In the face of challenges, animals must balance investments in
reproductive effort versus their own survival. Physiologically, this
tradeoff may be mediated by glucocorticoid release by the
hypothalamic-pituitary-adrenal (HPA) axis and prolactin release from the
pituitary to maintain parental care. The degree to which animals react to
and recover from stressors likely affects maintenance of parental behavior
and ultimately, fitness. However, less is known about how gaining parental
experience may alter hormonal stress responses and their underlying
neuroendocrine mechanisms. To address this gap, we measured the
corticosterone (CORT) and prolactin (PRL) stress response in both sexes of
the biparental rock dove (Columba livia) that had never raised chicks
versus birds that had fledged at least one chick. We measured both CORT
and PRL at baseline and after an acute stressor (30 minutes restraint). We
also measured negative feedback ability by administering dexamethasone, a
synthetic glucocorticoid that suppresses CORT release, and measured CORT
and PRL after 60 minutes. All hormones we measured when birds were not
actively nesting to assess whether effects of parental experience extend
beyond the breeding bout. Experienced birds had lower stress-induced and
negative-feedback CORT, and higher stress-induced PRL than inexperienced
birds. In a separate experiment, we measured glucocorticoid receptor
subtype expression in the hippocampus, a key site of negative feedback
regulation. Experienced birds expressed higher glucocorticoid receptors
than inexperienced controls, which may mediate their ability to attenuate
CORT release. Together, these results shed light on potential mechanisms
by which gaining experience may improve parental performance and fitness.