Effect of Ocular Enucleation and Altered Lighting Regimens at Various Ages on the Circadian Periodicity of Plasma Corticosteroid Levels in the Rat

Abstract

The circadian periodicity of plasma corticosteroid levels was studied in control and experimental groups of 30 and 80-day-old rats by means of blood sampling every 4 hr over a 48-hr period. Experimental groups consisted of: 1) animals born and reared under normal light-dark conditions, constant light (CL) or constant dark (CD) until age of study; 2) animals enucleated either at birth or on the 14th or 30th day of life and reared under normal light-dark conditions until age of study; 3) animals born and reared in CL or CD until 14 or 30 days of age and then maintained under normal light dark conditions until age of study, and 4) animals born and reared under normal light-dark conditions until the 14th, 30th or 60th day of life and then maintained in CL or CD until age of study. The results indicate that normal circadian periodicity of plasma corticosteroid levels, once established, does not persist if the animal is subsequently enucleated or exposed to either CL or CD. Animals reared in CL or CD from birth...