Adrenal response of male rats exposed to prenatal stress and early postnatal stimulation

Stress in pregnant rats caused by chronic immobilization alters the pattern of secretion of corticosterone and modifies the hypothalamic-pituitary-adrenal axis (HPA) of the fetus. Early postnatal handling, however, may reverse the effects of increased secretion of corticosterone. We investigated the effects of prenatal stress and postnatal handling on the activity of the HPA axis of male offspring of stressed female rats. Male 90-day-old rats from four groups were investigated: prenatally stressed animals without postnatal handling, prenatally stressed animals with postnatal handling, unstressed control animals with postnatal handling, and unstressed control animals without postnatal handling. After sacrifice, the adrenal glands were weighed to determine the adrenal-somatic index. Apoptosis was evaluated by TUNEL assay and active caspase-3 expression. We found that the adrenal gland cortex:medulla ratio increased in animals with prenatal stress and that eventually the stress caused apoptosis. Handling newborns to simulate maternal activity ameliorated some of the negative effects of prenatal stress.

Neuroendocrine changes and natriuresis in response to social stress in rats

Sympathetic activation is detected by the tachycardic, hypertensive and hyperthermic responses during social conflicts in rodents and primates. Sympathetic nervous system activation promoting sodium retention has long been recognized to play a significant role in the development and maintenance of salt-sensitive hypertension. The objective was to investigate neuroendocrine activation and renal sodium excretion in response to chronic social stress. Male Wistar rats were subjected to social stress in accordance with the resident-intruder paradigm. Intruder rats were subjected to social confrontation once daily for 6 days. After the last confrontation, plasma corticosterone and urinary catecholamines were determined to assess the neuroendocrine activation. Plasma aldosterone, plasma and urinary creatinine, Na(+) , K(+) and urinary volume were also measured. Chronic social stress increased the urinary norepinephrine, dopamine and plasma corticosterone levels, with no changes in epinephrine levels. On the other hand, high plasma aldosterone levels and low urinary sodium excretion without differences in creatinine clearance were observed. In conclusion, social stress had a strong antinatriuretic effect, which is coincident with noradrenergic and corticoadrenal activation and an increase in plasma aldosterone levels. Activation of these factors may promote sodium retention, which has long been recognized to play a significant role in the development and maintenance of hypertension.