Hypothalamic-Pituitary-Adrenal Axis Altered By Light in Mice

Fewer hours of light affect learning and memory

MONDAY, July 16 (HealthDay News) -- Mice exposed to shorter days during seasonal changes have changes in their feedback regulation of the hypothalamic-pituitary-adrenal axis and altered learning and memory, according to the results of a study in the July issue of Endocrinology.

Randy J. Nelson, Ph.D., and colleagues from Ohio State University in Columbus examined the effect of long (16 hours light/dark) and short (eight hours light/dark) photoperiods at the level of the hypothalamic-pituitary-adrenal axis on adult male mice.

The researchers found that short days increased corticosterone responses to restraint and altered negative feedback regulation of the hypothalamic-pituitary-adrenal axis as determined by increased glucocorticoid receptor expression in the hippocampus and increased sensitivity to dexamethasone suppression of corticosterone. They also found that short days altered spatial learning and memory due to task-associated stress responses.

"Overall, these results suggest that photoperiod-evoked modification of the hypothalamic-pituitary-adrenal axis and its potential behavioral consequences may be adaptive for winter survival," Nelson and colleagues conclude.

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