Time course of the effect of maternal deprivation on the hypothalamic‐pituitary‐adrenal axis in the infant rat

Abstract

Prolonged (i.e., 24-hr) maternal deprivation leads to a marked disinhibition of the infant rat's adrenocortical response to stress and/or ACTH. In the following study we examined the time course over which these effects develop. Pups were maternally deprived for varying lengths of time (i.e., 0, 2, 4, 8, & 24 hr); at the end of this period, corticosterone (CORT) secretion in response to stress (novelty or novelty plus saline injection) and ACTH injection was measured. Basal levels of CORT increased progressively over time in 7- and 11- (but not 3-) day-old pups. CORT release in response to stress followed a similar pattern. In contrast, ACTH injection resulted in marked increases in CORT levels regardless of the length of maternal deprivation in 3-day-old animals; at older ages, however, 24 hr of deprivation led to a much larger increase. These findings support the hypothesis that the hypothalamic-pituitary-adrenal axis of the neonatal rat is subject to maternal regulation.

Neuronal activity and stress differentially regulate hippocampal and hypothalamic corticotropin-releasing hormone expression in the immature rat

“…57 The neuroendocrine effects of CRH, the key mediator of the stress response, originate from clusters of peptidergic cells in the hypothalamic paraventricular nucleus (PVN). 24,34 CRH also functions as a neuromodulator in a number of …”

Effects of maternal and sibling deprivation on basal and stress induced hypothalamic-pituitary-adrenal components in the infant rat

“…This is followed by a 'compensatory' increase in CRH-mRNA abundance in the hypothalamic PVN [7,10,21]. We have established that CRH-mRNA abundance in the PVN does not increase subsequent to maximal tolerated acute-cold stress in rats aged 4 or 6 days, The infant hypothalamic-pituitary-adrenal (HPA) axis is under maternal regulation [6,9,13,16,17]. Prolonged, 24 h maternal deprivation has been found to increase basal plasma corticosterone (CORT) levels and to enhance HPA axis responsiveness to further stressors [6,9,16].…”

“…We have established that CRH-mRNA abundance in the PVN does not increase subsequent to maximal tolerated acute-cold stress in rats aged 4 or 6 days, The infant hypothalamic-pituitary-adrenal (HPA) axis is under maternal regulation [6,9,13,16,17]. Prolonged, 24 h maternal deprivation has been found to increase basal plasma corticosterone (CORT) levels and to enhance HPA axis responsiveness to further stressors [6,9,16]. Shorter periods of maternal deprivation (1, 2, 4, and 8 h) have been shown to have only a minimal effect on basal CORT levels and the response to acute stress [9,16].…”

“…Using this paradigm, maternal deprivation alone resulted in an increased basal and acute stress-induced plasma CORT level compared to maternal and sibling deprivation. This was not associated with excess weight loss in either group (see above), excluding thermal-loss as the cause of the enhanced stress response.What mechanisms [8,9,[12][13][14]19] mediated the increased basal and cold-induced plasma CORT subsequent to maternal deprivation? An increase of basal plasma CORT and PVN-CRH-mRNA abundance in adult rats subjected to maternal separation in infancy has been reported [16].…”

Interaction of nitric oxide and serotonin in aggressive behavior

“…Alterations in stress-related hormones are also reported (Levine et al, 1991). Twenty-four hour maternal deprivation on postnatal day (PD) 14 elevates basal and stressinduced corticosterone levels, as well as decreases its receptors in the hippocampus of rats (Vazquez et al, 2002).…”