Estrogen stimulates gonadotropin-releasing hormone release from rat hypothalamus independently through catecholamine and histamine in vitro.
Estradiol is known to stimulate gonadotropin-releasing hormone release from the rat medio-basal hypothalamus. Studies were made in an in vitro perifusion system on whether catecholamine and/or histamine was involved in estradiol-induced GnRH release. Normal cycling female rats were decapitated in diestrus II and their medio-basal hypothalami were combined and, perifused with Earl's balanced salt solution containing 0.01% bovine serum albumin bubbled with 95% O2 and 5% CO2. The levels of norepinephrine, dopamine, and histamine and of GnRH in the effluent were measured by HPLC and radioimmunoassay, respectively. Administration of 10(-6) mol/l estradiol resulted in releases of norepinephrine, dopamine, histamine and GnRH at levels of 98, 70, 91 and 288%, respectively, of initial values. Administration of 10(-6) mol/l norepinephrine or dopamine resulted in no increase in histamine release, and administration of 10(-6) mol/l histamine did not increase release of norepinephrine or dopamine. These data suggest that estradiol stimulates the releases of GnRH, catecholamine and histamine from the rat medio-basal hypothalamus, and that it increases GnRH release independently through catecholamine and histamine. As we found previously that norepinephrine or histamine stimulates GnRH release from the medio-basal hypothalamus, we conclude that estradiol stimulates releases of norepinephrine and histamine, resulting in GnRH release from the medio-basal hypothalamus.
Ohtsuka
S
S
Department of Obstetrics and Gynecology, Osaka University Medical School, Japan.
Nishizaki
T
T
Tasaka
K
K
Miyake
A
A
Tanizawa
O
O
Yamatodani
A
A
Wada
H
H
D000818:Animals; D004298:Dopamine / Q000378:metabolism; D004958:Estradiol / Q000494:pharmacology*; D005260:Female; D006636:Histamine Release / Q000187:drug effects; D007033:Hypothalamus, Middle / Q000378:metabolism*; D009638:Norepinephrine / Q000378:metabolism; D010906:Pituitary Hormone-Releasing Hormones / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains
D010906:Pituitary Hormone-Releasing Hormones; D004958:Estradiol; D004298:Dopamine; D009638:Norepinephrine