Stimulatory effects of quinpirole hydrochloride, D2-dopamine receptor agonist, at low concentrations on prolactin release in female rats in vitro.
Dopamine (DA) has dual actions (inhibitory and stimulatory) in the regulation of prolactin (PRL) release, depending on its concentration. To investigate the stimulatory effects of DA, perifused rat anterior pituitary cells were exposed to the highly-specific DA D2 receptor agonist, quinpirole hydrochloride (LY). Very low concentrations of LY (10(-12)-10(-10) M) stimulated PRL release and potentiated thyrotropin-releasing hormone (TRH)-induced PRL release. Higher concentrations of LY did not stimulate. Pretreatment with pertussis toxin (30 ng/ml, 24 h) completely abolished these effects of LY. The D2 receptor antagonist, metoclopramide, also blocked the potentiation by LY of TRH-induced PRL release. These data indicate that very low concentrations of dopamine stimulate PRL release via an interaction with a D2 receptor connected to a pertussis toxin-sensitive G protein.
Tagawa
R
R
First Department of Internal Medicine, Kagawa Medical School, Japan.
Takahara
J
J
Sato
M
M
Niimi
M
M
Murao
K
K
Ishida
T
T
D000818:Animals; D002478:Cells, Cultured; D015259:Dopamine Agents / Q000494:pharmacology*; D018492:Dopamine Antagonists; D004305:Dose-Response Relationship, Drug; D004873:Ergolines / Q000494:pharmacology*; D005260:Female; D008787:Metoclopramide / Q000494:pharmacology; D037342:Pertussis Toxin; D010903:Pituitary Gland, Anterior / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D011388:Prolactin / Q000378:metabolism*; D019257:Quinpirole; D051381:Rats; D011919:Rats, Inbred Strains; D011954:Receptors, Dopamine / Q000187:drug effects; D017448:Receptors, Dopamine D2; D013973:Thyrotropin-Releasing Hormone / Q000494:pharmacology; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D015259:Dopamine Agents; D018492:Dopamine Antagonists; D004873:Ergolines; D011954:Receptors, Dopamine; D017448:Receptors, Dopamine D2; D010566:Virulence Factors, Bordetella; D019257:Quinpirole; D013973:Thyrotropin-Releasing Hormone; D011388:Prolactin; D037342:Pertussis Toxin; D008787:Metoclopramide