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SLEEP AND TEMPERATURE REGULATION

Inhibiting cortisol response accelerates recovery from a photic phase shift

Department of Psychology, University of Michigan, Ann Arbor, Michigan

Submitted 27 April 2004 ; accepted in final form 20 August 2004

Jetlag results when a temporary loss of circadian entrainment alters phase relationships among internal rhythms and between an organism and the outside world. After a large shift in the light-dark (LD) cycle, rapid recovery of entrainment minimizes the negative effects of internal circadian disorganization. There is evidence in the existing literature for an activation of the hypothalamic-pituitary-adrenal (HPA) axis after a photic phase shift, and it is possible that the degree of HPA-axis response is a determining factor of reentrainment time. This study utilized a diurnal rodent, Octodon degus, to test the prediction that the alteration of cortisol levels would affect the reentrainment rate of circadian locomotor rhythms. In experiment 1, we examined the effects of decreased cortisol (using metyrapone, an 11-hydroxylase inhibitor) on the rate of running-wheel rhythm recovery after a 6-h photic phase advance. Metyrapone treatment significantly shortened the length of time it took animals to entrain to the new LD cycle (11.5% acceleration). In experiment 2, we examined the effects of increased cortisol on the rate of reentrainment after a 6-h photic phase advance. Increasing plasma cortisol levels increased the number of days (8%) animals took to reentrain running-wheel activity rhythms, but this effect did not reach significance. A third experiment replicated the results of experiment 1 and also demonstrated that suppression of HPA activity via dexamethasone injection is capable of accelerating reentrainment rates by 33%. These studies provide support for an interaction between the stress axis and circadian rhythms in determining the rate of recovery from a phase shift of the LD cycle.

stress; circadian rhythm; metyrapone; dexamethasone; entrainment

This article has been cited by other articles:

				T. J. Jechura, M. M. Mahoney, C. D. Stimpson, and T. M. Lee Odor-specific effects on reentrainment following phase advances in the diurnal rodent, Octodon degus Am J Physiol Regulatory Integrative Comp Physiol, December 1, 2006; 291(6): R1808 - R1816. [Abstract] [Full Text] [PDF]

				J. A. Mohawk and T. M. Lee Restraint Stress Delays Reentrainment in Male and Female Diurnal and Nocturnal Rodents J Biol Rhythms, June 1, 2005; 20(3): 245 - 256. [Abstract] [PDF]