Postnatal maternal separation during the stress hyporesponsive period enhances the adrenocortical response to novelty in adult rats by affecting feedback regulation in the CA1 hippocampal field

Abstract

The aim of the present experiment was to study the effects of early postnatal maternal separation on behavioural and adrenocortical responses to novelty in rats tested as adults. Sprague-Dawley rat pups were exposed to daily maternal separation (5 h/day) from postnatal day 2 to 6, during the stress hyporesponsive period. Since this procedure requires physical contact with the animals, a first control group of daily handled pups was introduced. A second control group, consisting of pups never handled or separated from the mother, was also considered. At postnatal day 45, the rats were tested in a two-compartment exploratory apparatus: the maternally separated and the non-handled rats, whose behavioural performance did not differ, showed higher emotional behaviour when compared with the handled rats (P < 0.05), suggesting that the handling procedure but not maternal separation improved the capacity to cope with novelty. Corticosterone plasma levels were found to be higher in the maternally separated rats than in the other two groups (P < 0.05), either at resting conditions or at 30 min after novelty exposure (P < 0.05). Levels of nuclear glucocorticoid receptor immunoreactivity in the CA1 hippocampal field were shown to be regulated by novelty exposure, as expected, in both the handled and the non-handled rats but not in the maternally separated rats. In conclusion, repeated maternal separation periods of 5 h/day during the first week of life produced long-lasting effects on the hippocampal regulation of the hypothalamic-pituitary-adrenocortical axis, which appear to be associated with increased responsiveness to stress stimuli in adulthood.

Modulation of synaptic plasticity by short-term aerobic exercise in adult mice

“…Biagini et al, reported that glucocorticoid receptors immune reactivity in the CA1 hippocampal area of rats exposed to repeated stress was higher than in unstressed control rats and furthermore that the intensity of specific immunoreactivity of hippocampal pyramidal cells can be taken as an index of hypothalamic pituitary adrenocortical (HPA) axis activation and therefore of corticosterone secretion [21]. Moreover, repeated maternal separation periods of 5 h/day during the first week of life produced long lasting effects on the hippocampal regulation of the HPA axis which appear to be associated with increased responsiveness to stress stimuli in adulthood [22].…”

Weight gain, behavioral and cortisol changes after orchiectomy with or without local anaesthesia in piglets

“…Pigs, like other species, are very sensitive to separation from their mothers (PLOTSKY; MEANEY, 1993;BIAGINI et al, 1998;WIGGE;NEUMANN, 1999). The reduction in the serum cortisol concentration at 3 and 6 days after surgery in both groups is probably related to the fact that at these time points, the duration of the handling period was shorter than that immediately after surgery and the piglets were restrained only for blood sampling.…”

Early life stress downregulates endothelin receptor expression and enhances acute stress-mediated blood pressure responses in adult rats

“…Maternal separation is a widely used animal model of early life stress and chronic behavioral stress (20). Rat pups separated from their mothers daily for a prolonged period (up to 3 h) during the hyporesponsive period display abnormal anxiety-related behavior (41, 43), as well as increased acute behavioral and endocrine stress reactivity as adults (4,27,38,44).Individuals with increased susceptibility to stressors may also have an exacerbated rise in blood pressure (26). Acute stressors induce many physiological responses, and greater reactivity to stress or delayed poststress recovery predicts future cardiovascular disease risk (7), such as stroke (14), hypertension (37), and preclinical atherosclerosis (23,52).…”

“…Maternal separation is a widely used animal model of early life stress and chronic behavioral stress (20). Rat pups separated from their mothers daily for a prolonged period (up to 3 h) during the hyporesponsive period display abnormal anxiety-related behavior (41, 43), as well as increased acute behavioral and endocrine stress reactivity as adults (4,27,38,44).…”