Abstract
Summary
Data are presented here which verify that immature rats exhibit no cir-cadian fluctuation of mitoses in the corneal epithelium prior to the third week of life. These data indicate that dexamethasone administration induces age-dependent alterations in the circadian mitotic pattern of the corneal epithelium. Nine day old animals still revealed no rhythmic component in circadian mitotic activity after dexamethasone treatment. Eleven-, 12- and 13-day old animals treated with dexamethasone exhibited circadian cycles which looked qualitatively like the circadian rhythm of the 15-day old animal. Fifteen-day old animals responded with a synchrony of mitotic activity at 0700 hr and a generalized decrease in mitotic activity. The possible dependence of these responses upon existing circadian mitotic activity and maturation of the central nervous system and/or the glucocorticoid target tissue is discussed.
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