Aging progressively decreases the densities and alters the diurnal rhythms of alpha 1-adrenergic receptors in selected hypothalamic regions.
Associated with the decline in reproductive function that occurs with age in female rats are a diminished ability to secrete LH in response to ovariectomy as well as alterations in the preovulatory LH surge mechanisms. The noradrenergic system, an important regulator of LH release, exhibits age-related alterations in the pattern of neurotransmitter release. In addition, the density of alpha 1-receptors changes in intact old rats. To determine whether age-related changes in the pulsatile pattern of LH secretion are associated with declines in the densities and/or a loss of diurnal rhythm of alpha 1-receptors, we measured the density of alpha 1-receptors at various times of day in young, middle-aged, and old ovariectomized rats. By middle-age, mean concentrations of alpha 1-receptors decline in the median eminence and suprachiasmatic nucleus. By old age, mean concentrations of alpha 1-receptors decline in all regions of the hypothalamus examined but not in the dorsal lateral septum. In addition, the diurnal rhythms in alpha 1-receptors, which occur in the medial preoptic nucleus and the suprachiasmatic nucleus of young rats, are lost by middle-age. These data indicate that progressive alterations in the mean concentrations and diurnal rhythms of alpha 1-receptors occur with age in brain regions important for the regulation of reproductive functions and may contribute to the age-associated deficits in LH secretion.
Weiland
N G
NG
Department of Physiology, School of Medicine, University of Maryland, Baltimore 21201.
Wise
P M
PM
D000375:Aging / Q000378:metabolism*; D000818:Animals; D002940:Circadian Rhythm; D005260:Female; D007031:Hypothalamus / Q000378:metabolism*; D007986:Luteinizing Hormone / Q000378:metabolism; D008473:Median Eminence / Q000378:metabolism; D010052:Ovariectomy; D011301:Preoptic Area / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D011942:Receptors, Adrenergic, alpha / Q000378:metabolism*; D013493:Suprachiasmatic Nucleus / Q000378:metabolism; D014697:Ventromedial Hypothalamic Nucleus / Q000378:metabolism
D011942:Receptors, Adrenergic, alpha; D007986:Luteinizing Hormone