title: Effects of pinealectomy and aging on the serum corticosterone circadian rhythm in rats.
abstract: Male Sprague-Dawley rats were housed in alternate light/dark conditions (light on, 7:00 AM, light off, 7:00 PM). Corticosterone was determined by radioimmunoassay from blood samples that were obtained by tail clip at 4-h intervals. Pinealectomized animals have shown significant increase of corticosterone levels at 7:00 AM, 11:00 AM and 7:00 PM in comparison with 2-month-old intact rats. There were no differences in serum corticosterone rhythm between 24-month-old and pinealectomized animals. Twelve-month-old rats have shown significant increase of corticosterone levels at 7:00 and 11:00 AM in comparison with 2-month-old animals. The age-associated increase of serum corticosterone and the similarity between serum corticosterone circadian rhythm in aged and pinealectomized animals suggest that an age-related decrease in melatonin production [Reiter et al., 1981] may contribute to age related changes of hypothalamic-pituitary adrenal axis regulation.
mesh_terms: D000375:Aging; D000818:Animals; D002940:Circadian Rhythm; D003345:Corticosterone / Q000097:blood*; D008297:Male; D010870:Pineal Gland / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D003345:Corticosterone