Journal of Neuroscience, Vol 7, 3469-3473, Copyright © 1987 by Society for Neuroscience
Diurnal rhythmicity and hypothalamic deficits in glucose utilization in aged ovariectomized rats
PM Wise, RC Walovitch, IR Cohen, NG Weiland and ED London
Department of Physiology, School of Medicine, University of Maryland, Baltimore 21201.
Aging is associated with a loss of cyclic gonadotropin release in female
animals. This deficit may reflect dampened circadian rhythmicity of
neuroendocrine events and/or altered function in hypothalamic nuclei
important to regulation of cyclic female reproduction. The purpose of this
study was to determine if diurnal periodicity and glucose metabolism in the
hypothalamus are altered with age and whether such changes could help to
explain the age-related deficits in gonadotropin release. Young
(3-4-month-old) and old (18-21-month-old) rats were ovariectomized and
subjected to the 2-deoxy-D-1-14C-glucose technique to measure rates of
cerebral glucose utilization (GU), an index of neural function (Sokoloff et
al., 1977) in various brain areas and in the pineal gland. We measured GU
during the light (1400 hours) and the dark (2200 hours) in 17 anatomical
regions including the following hypothalamic areas: medial preoptic
nucleus, suprachiasmatic preoptic nucleus, suprachiasmatic nucleus,
paraventricular nucleus, arcuate nucleus, and median eminence. Serum
concentrations of luteinizing hormone (LH) and prolactin were measured in
the same rats to determine the effect of age on both of these hormones.
Diurnal periodicity of GU was observed in the suprachiasmatic nucleus and
the pineal gland in young and old rats. Although there was no age
difference in GU of the pineal gland, GU was reduced during the light and
dark in the suprachiasmatic nucleus and all other hypothalamic areas
examined except the suprachiasmatic preoptic nucleus and the median
eminence. Ovariectomy induced an attenuated increase in concentrations of
LH in old, compared to young rats.(ABSTRACT TRUNCATED AT 250 WORDS)