Altered Entrainment to the Day/Night Cycle Attenuates the Daily Rise in Circulating Corticosterone in the Mouse

Authors

Patricia J. Sollars, University of Nebraska-LincolnFollow
Michael J. Weiser, Colorado State University
Andrea E. Kudwa, Colorado State University
Jayne R. Bramley, Colorado State University
Malcolm D. Ogilvie, Colorado State University
Robert L. Spencer, University of Colorado
Robert J. Handa, Colorado State University
Gary E. Pickard, Colorado State UniversityFollow

Document Type

Article

Date of this Version

2014

Citation

Sollars PJ, Weiser MJ, Kudwa AE, Bramley JR, Ogilvie MD, et al. (2014) Altered Entrainment to the Day/Night Cycle Attenuates the Daily Rise in Circulating Corticosterone in the Mouse. PLoS ONE 9(11): e111944. doi:10.1371/journal.pone.0111944

Comments

Copyright 2014 Sollars et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License.

Abstract

The suprachiasmatic nucleus (SCN) is a circadian oscillator entrained to the day/night cycle via input from the retina. Serotonin (5-HT) afferents to the SCN modulate retinal signals via activation of 5-HT_1B receptors, decreasing responsiveness to light. Consequently, 5-HT_1B receptor knockout (KO) mice entrain to the day/night cycle with delayed activity onsets. Since circulating corticosterone levels exhibit a robust daily rhythm peaking around activity onset, we asked whether delayed entrainment of activity onsets affects rhythmic corticosterone secretion. Wheel-running activity and plasma corticosterone were monitored in mice housed under several different lighting regimens. Both duration of the light:dark cycle (T cycle) and the duration of light within that cycle was altered. 5-HT_1B KO mice that entrained to a 9.5L:13.5D (short day in a T = 23 h) cycle with activity onsets delayed more than 4 h after light offset exhibited a corticosterone rhythm in phase with activity rhythms but reduced 50% in amplitude compared to animals that initiated daily activity ,4 h after light offset. Wild type mice in 8L:14D (short day in a T = 22 h) conditions with highly delayed activity onsets also exhibited a 50% reduction in peak plasma corticosterone levels. Exogenous adrenocorticotropin (ACTH) stimulation in animals exhibiting highly delayed entrainment suggested that the endogenous rhythm of adrenal responsiveness to ACTH remained aligned with SCN-driven behavioral activity. Circadian clock gene expression in the adrenal cortex of these same animals suggested that the adrenal circadian clock was also aligned with SCN-driven behavior. Under T cycles ,24 h, altered circadian entrainment to short day (winter-like) conditions, manifest as long delays in activity onset after light offset, severely reduces the amplitude of the diurnal rhythm of plasma corticosterone. Such a pronounced reduction in the glucocorticoid rhythm may alter rhythmic gene expression in the central nervous system and in peripheral organs contributing to an array of potential pathophysiologies.