Effect of adrenalectomy and dexamethasone treatment on circadian running in the rat.

Although adrenalectomy resulted in a marked decrease in total wheel running activity in male rats, the circadian rhythm of the running was not altered. Contrary to what has been previously observed in animals with intact adrenal glands, administration of the synthetic glucocorticoid dexamethasone to adrenalectomized animals resulted in an immediate increase in the amount of running with no effect on the circadian distribution of running. It was concluded that the adrenal axis had an influence on an animal's ability to express running behavior, but the adrenal axis had no influence on the neural control of the circadian rhythm of running.