Involvement of norepinephrine activity in the regulation of. cap alpha. 1 adrenergic receptors in the medial preoptic nucleus of estradiol-treated rats

Journal Article · Sun Jan 01 04:00:00 EST 1989 · Life Sci.; (United States)

DOI:https://doi.org/10.1016/0024-3205(89)90318-4· OSTI ID:5905264

Sortino, M A; Weiland, N G; Wise, P M

To establish whether the diurnal decrease in the density of ..cap alpha..1 receptors observed in the medial preoptic nucleus (MPN) of estrogen (E/sub 2/)-treated rats is related to the concomitant diurnal increase in norepinephrine (NE) turnover rates, we quantitiated the density of (/sup 3/H)-Prazosin binding to ..cap alpha..1 receptors after blockade of NE turnover with alpha-methyl-paratyrosine (..cap alpha..MPT). A series of preliminary studies was performed to rule out an interference of this drug with (/sup 3/H)-Prazosin binding to ..cap alpha..1 adrenergic receptors in vitro and in vivo. Incubation of brain slices with ..cap alpha..MPT produced a dose-dependent inhibition of (/sup 3/H)-Prazosin binding to ..cap alpha..1 adrenergic receptors with an IC/sub 50/ of approximately 6 mM. Scatchard analysis demonstrated that ..cap alpha..MPT exhibited a simple competitive interaction with (/sup 3/H)-Prazosin binding sites as shown by an increase in the apparent dissociation constant (Kd) of the ligand and no change in the number of ..cap alpha..1 receptors (B/sub max/). In contrast, preincubation of brain slices with ..cap alpha..MPT and prior in vivo administration of ..cap alpha..MPT did not affect (/sup 3/H)-Prazosin binding to ..cap alpha..1 adrenergic receptors. The density of ..cap alpha..1 adrenergic receptors in MPN was quantitated autoradiographically. Blockade of NE turnover with ..cap alpha..MPT only partially prevented the reduction in ..cap alpha..1 receptor density observed in the E/sub 2/-treated rats, suggesting that the decrease in the level of (/sup 3/H)-Prazosin binding sites cannot be completely ascribed to increased NE turnover rates.

• Research Organization: Univ. of Maryland, Baltimore (USA)
• OSTI ID: 5905264
• Journal Information: Life Sci.; (United States), Journal Name: Life Sci.; (United States) Vol. 44:17; ISSN LIFSA
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ADRENAL HORMONES
ANIMALS
AUTONOMIC NERVOUS SYSTEM AGENTS
AUTORADIOGRAPHY
BIOCHEMICAL REACTION KINETICS
BODY
BRAIN
CARDIOTONICS
CARDIOVASCULAR AGENTS
CENTRAL NERVOUS SYSTEM
DAILY VARIATIONS
DOSE-RESPONSE RELATIONSHIPS
DRUGS
ESTRADIOL
ESTRANES
ESTROGENS
HORMONES
HYDROXY COMPOUNDS
KINETICS
LABELLED COMPOUNDS
MAMMALS
MEMBRANE PROTEINS
METABOLISM
NERVOUS SYSTEM
NEUROREGULATORS
NORADRENALINE
ORGANIC COMPOUNDS
ORGANS
PROTEINS
RATS
REACTION KINETICS
RECEPTORS
RODENTS
STEROID HORMONES
STEROIDS
SYMPATHOMIMETICS
TRITIUM COMPOUNDS
VARIATIONS
VERTEBRATES