Estrogen alters the diurnal rhythm of alpha 1-adrenergic receptor densities in selected brain regions
Norepinephrine regulates the proestrous and estradiol-induced LH surge by binding to alpha 1-adrenergic receptors. The density of alpha 1-receptors may be regulated by estradiol, photoperiod, and noradrenergic neuronal activity. We wished to determine whether alpha 1-receptors exhibit a diurnal rhythm in ovariectomized and/or estradiol-treated female rats, whether estradiol regulates alpha 1-receptors in those areas of brain involved with LH secretion and/or sexual behavior, and whether the concentrations of alpha-receptors vary inversely relative to previously reported norepinephrine turnover patterns. Young female rats, maintained on a 14:10 light-dark cycle were ovariectomized. One week later, half of them were outfitted sc with Silastic capsules containing estradiol. Groups of animals were decapitated 2 days later at 0300, 1000, 1300, 1500, 1800, and 2300 h. Brains were removed, frozen, and sectioned at 20 micron. Sections were incubated with (/sup 3/H)prazosin in Tris-HCl buffer, washed, dried, and exposed to LKB Ultrofilm. The densities of alpha 1-receptors were quantitated using a computerized image analysis system. In ovariectomized rats, the density of alpha 1-receptors exhibited a diurnal rhythm in the suprachiasmatic nucleus (SCN), medial preoptic nucleus (MPN), and pineal gland. In SCN and MPN, receptor concentrations were lowest during the middle of the day and rose to peak levels at 1800 h. In the pineal gland, the density of alpha 1-receptors was lowest at middark phase, rose to peak levels before lights on, and remained elevated during the day. Estradiol suppressed the density of alpha 1 binding sites in the SCN, MPN, median eminence, ventromedial nucleus, and the pineal gland but had no effect on the lateral septum. Estrogen treatment altered the rhythm of receptor densities in MPN, median eminence, and the pineal gland.
- Research Organization:
- Univ. of Maryland, Baltimore
- OSTI ID:
- 5670126
- Journal Information:
- Endocrinology; (United States), Vol. 121:5
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ESTRADIOL
BIOCHEMICAL REACTION KINETICS
LH
SECRETION
RECEPTORS
DENSITY
SYMPATHOMIMETICS
AUTORADIOGRAPHY
BRAIN
DAILY VARIATIONS
NORADRENALINE
PINEAL GLAND
RATS
TRITIUM COMPOUNDS
ADRENAL HORMONES
ANIMALS
AUTONOMIC NERVOUS SYSTEM AGENTS
BODY
CARDIOTONICS
CARDIOVASCULAR AGENTS
CENTRAL NERVOUS SYSTEM
DRUGS
ESTRANES
ESTROGENS
GLANDS
GONADOTROPINS
HORMONES
HYDROXY COMPOUNDS
KINETICS
LABELLED COMPOUNDS
MAMMALS
MEMBRANE PROTEINS
NERVOUS SYSTEM
NEUROREGULATORS
ORGANIC COMPOUNDS
ORGANS
PEPTIDE HORMONES
PHYSICAL PROPERTIES
PITUITARY HORMONES
PROTEINS
REACTION KINETICS
RODENTS
STEROID HORMONES
STEROIDS
VARIATIONS
VERTEBRATES
550201* - Biochemistry- Tracer Techniques