Adrenal-dependent and -independent stress-inducedPer1mRNA in hypothalamic paraventricular nucleus and prefrontal cortex of male and female rats

Nov 23, 2017Stress (Amsterdam, Netherlands)

Stress-related Per1 gene activity in stress control and thinking areas of male and female rats, with and without adrenal involvement

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Abstract

Acute restraint stress can rapidly (within 30 min) increase Per1 and cFos mRNA levels in the hypothalamic paraventricular nucleus and prefrontal cortex of male and female rats.

Oscillating clock gene expression contributes to molecular clocks in both the hypothalamic suprachiasmatic nucleus (SCN) and extra-SCN brain regions.
Extra-SCN molecular clocks rely on the SCN for synchronization with the light:dark cycle.
Stress-induced glucocorticoid secretion may disrupt the function of extra-SCN molecular clocks.
Increased Per1 mRNA in response to stress may represent a mechanism for extra-SCN clocks to adapt to environmental changes.
In the prefrontal cortex, the stress-induced increase in Per1 mRNA appears to occur independently of glucocorticoids.

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Oscillating clock gene expression gives rise to a molecular clock that is present not only in the body's master circadian pacemaker, the hypothalamic suprachiasmatic nucleus (SCN), but also in extra-SCN brain regions. These extra-SCN molecular clocks depend on the SCN for entrainment to a light:dark cycle. The SCN has limited neural efferents, so it may entrain extra-SCN molecular clocks through its well-established circadian control of glucocorticoid hormone secretion. Glucocorticoids can regulate the normal rhythmic expression of clock genes in some extra-SCN tissues. Untimely stress-induced glucocorticoid secretion may compromise extra-SCN molecular clock function. We examined whether acute restraint stress during the rat's inactive phase can rapidly (within 30 min) alter clock gene (Per1, Per2, Bmal1) and cFos mRNA (in situ hybridization) in the SCN, hypothalamic paraventricular nucleus (PVN), and prefrontal cortex (PFC) of male and female rats (6 rats per treatment group). Restraint stress increased Per1 and cFos mRNA in the PVN and PFC of both sexes. Stress also increased cFos mRNA in the SCN of male rats, but not when subsequently tested during their active phase. We also examined in male rats whether endogenous glucocorticoids are necessary for stress-induced Per1 mRNA (6-7 rats per treatment group). Adrenalectomy attenuated stress-induced Per1 mRNA in the PVN and ventral orbital cortex, but not in the medial PFC. These data indicate that increased Per1 mRNA may be a means by which extra-SCN molecular clocks adapt to environmental stimuli (e.g. stress), and in the PFC this effect is largely independent of glucocorticoids.

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Adrenal-dependent and -independent stress-inducedPer1mRNA in hypothalamic paraventricular nucleus and prefrontal cortex of male and female rats

Abstract

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