Changes in mediobasal hypothalamic dopamine and GABA release: a possible mechanism underlying taurine-induced prolactin secretion.
Taurine (Tau), a putative inhibitory amino acid neurotransmitter, has been shown to stimulate prolactin (PRL) release. Using ovariectomized, estrogen-replaced adult rats we investigated initially the effect of this amino acid, injected by different routes, on PRL secretion in vivo. Tau (100-500 mg/kg) had no effect on PRL release when given i.p.; 15 min after i.c.v. injection of Tau (3 mumoles), a significant increase in serum PRL levels was observed (78 +/- 9 ng/ml over basal levels, p < 0.01 vs. controls). In vitro (cultured anterior pituitary cells) PRL release was not affected by a 5 h incubation with Tau (10(-3)-10(-8) M). Basal dopamine (DA) or gamma-aminobutyric acid (GABA) output from superfused mediobasal hypothalamic fragments (MBH) was not affected by Tau (10(-3) M or 10(-5) M). However, during stimulation with KCl (50 mM), Tau (10(-3) M) significantly lowered DA release, and increased GABA output. It is concluded that Tau acts at a central level to increase PRL secretion, most probably by modulating the hypothalamic release of neurotransmitters controlling lactotroph function.
Arias
P
P
Departamento de Fisiología, Facultad de Medicina, Universidad de Buenos Aires, Argentina.
Jarry
H
H
Convertini
V
V
Ginzburg
M
M
Wuttke
W
W
Moguilevsky
J
J
D000818:Animals; D002478:Cells, Cultured; D004298:Dopamine / Q000378:metabolism*; D004967:Estrogens / Q000494:pharmacology; D005260:Female; D007033:Hypothalamus, Middle / Q000187:drug effects*; D066298:In Vitro Techniques; D007274:Injections, Intraperitoneal; D007276:Injections, Intraventricular; D010052:Ovariectomy; D010902:Pituitary Gland / Q000166:cytology / Q000187:drug effects; D011388:Prolactin / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D013654:Taurine / Q000494:pharmacology*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
D004967:Estrogens; D013654:Taurine; D005680:gamma-Aminobutyric Acid; D011388:Prolactin; D004298:Dopamine