Tamoxifen counteracts estradiol induced effects on striatal and hypophyseal dopamine receptors
We investigated the ability of Tamoxifen (TAM), an antiestrogen drug, to counteract the modification induced by estrogens on dopamine (DA) receptors on striatum and on adenohypophysis of ovex female rats. Subacute treatment with 17..beta..-estradiol (E/sub 2/) at both low (0.1 ..mu..g/kg) and high (20 ..mu..g/kg) doses confirmed its ability to increase the number of striatal /sup 3/H-Spiperone (/sup 3/H-SPI) binding sites in a dose dependent manner. By contrast in the pituitary, only high doses of estrogen were effective in reducing the number of DA receptors. We treated ovex female rats for 15 days with TAM alone or associated with E/sub 2/, to see if these estrogenic effects could be suppressed by an antiestrogenic drug. TAM did not affect the number of striatal DA receptors, but significantly increased the adenohypophy-seal DA binding sites, without varying their affinity. No changes were observed in pituitary and striatal DA receptor density, even when TAM was injected in association with estradiol. In conclusions: TAM is able to counteract the effects estrogens have on DA receptors. However there is some evidence that it could influence the pituitary DA systems independently of it antiestrogenic activity.
- Research Organization:
- Univ. of Turin (Italy)
- OSTI ID:
- 6412345
- Journal Information:
- Life Sci.; (United States), Journal Name: Life Sci.; (United States) Vol. 42:24; ISSN LIFSA
- Country of Publication:
- United States
- Language:
- English
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59 BASIC BIOLOGICAL SCIENCES
AMINES
ANIMALS
AROMATICS
AUTONOMIC NERVOUS SYSTEM AGENTS
BIOCHEMICAL REACTION KINETICS
BIOLOGICAL FUNCTIONS
BODY
CARDIOTONICS
CARDIOVASCULAR AGENTS
DOPAMINE
DOSE-RESPONSE RELATIONSHIPS
DRUGS
ENDOCRINE GLANDS
ESTRADIOL
ESTRANES
ESTROGENS
FUNCTIONS
GLANDS
HORMONES
HYDROXY COMPOUNDS
ISOTOPE APPLICATIONS
KINETICS
LABELLED COMPOUNDS
MAMMALS
MEMBRANE PROTEINS
NEUROREGULATORS
ORGANIC COMPOUNDS
ORGANS
PHENOLS
PITUITARY GLAND
POLYPHENOLS
PROTEINS
RATS
REACTION KINETICS
RECEPTORS
RODENTS
STEROID HORMONES
STEROIDS
SYMPATHOMIMETICS
TRACER TECHNIQUES
TRITIUM COMPOUNDS
VERTEBRATES