Age-related changes in the diurnal rhythm of corticotropin
releasing hormone gene expression in the paraventricular nuclei
1.
Cai, Aihua, and Phyllis M. Wise.
Department of Physiology, University of Maryland at Baltimore,
Baltimore, MD 21201, Department of Physiology, University of
Kentucky, Lexington, KY 40536
APStracts 2:0186E, 1995.
A circadian rhythm secretion of corticotropin releasing hormone (CRH)
is thought to regulate the circadian pattern of secretion of ACTH and
corticosterone. We have previously reported that the amplitude of the
diurnal rhythm of serum corticosterone concentrations decreases in
17-20 month old rats. In the present experiment we tested whether an
age-related alteration in the daily rhythm and/or level of CRH mRNA
in the paraventricular nuclei (PVN) occur during middle-age. Groups
of young and middle-aged animals were killed at several times of day.
We assessed the level of CRH mRNA in the PVN and dorsal medial
subdivision of the PVN using in situ hybridization. In young rats,
CRH mRNA expression exhibited a diurnal rhythm in the dorsal medial
PVN. The same trend was observed in the entire medial PVN. In middle
-aged rats no rhythm was detected in either region. The overall
average level of CRH mRNA was not different between these two age
groups. These findings suggest that changes in the suprachiasmtic
nucleus (SCN) or its ability to entrain neuroendocrine outputs occur
relatively early during the aging process.
Received 9 March 1995; accepted in final form 21 August 1995.
APS Manuscript Number E110-5.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 23 September 1995.