Prolactin secretion after bromocriptine in the hypophysial stalk-transfected gilt.
Blood samples were collected by jugular vein cannula from 6 hypophysial stalk-transected (HST) and 4 intact (INTACT) crossbred gilts at 0800, 0830 and 0900 h. Immediately after the 0900 h sample, thyrotropin releasing hormone (TRH) was injected i.v. to determine anterior pituitary gland response via release of prolactin (PRL). Blood was collected every 15 min for 1 h and every 30 min for an additional 2 h. All gilts received the dopamine (DA) agonist, bromocriptine (CB-154), s.c. at 1600 h and blood sampling and TRH challenge was repeated beginning at 0800 h the next day. Mean serum PRL concentration at 0800, 0830 and 0900 h was termed basal PRL for each day. Before CB-154, basal PRL for HST gilts was greater (P < .01) than for INTACT gilts, whereas, after CB-154, basal PRL were similar among HST and INTACT gilts. Before CB-154, TRH caused peak secretion of PRL of similar magnitude within 15 minutes in both HST and INTACT gilts; PRL decreased to basal concentration by 120 min after TRH in both groups. However, after CB-154, PRL response to TRH was blunted similarly in all gilts. These results indicate that suppression of DA pathways is an antecedent to the physiological mechanism by which a secretagogue, such as TRH, stimulates PRL secretion in the intact pig.
Kraeling
R R
RR
USDA-ARS, R. B. Russell Research Center, Athens, GA 30613.
Estienne
M J
MJ
Barb
C R
CR
Rampacek
G B
GB
D000818:Animals; D001971:Bromocriptine / Q000494:pharmacology*; D004298:Dopamine / Q000502:physiology; D005260:Female; D007016:Hypophysectomy / Q000662:veterinary; D007030:Hypothalamo-Hypophyseal System / Q000187:drug effects / Q000502:physiology*; D010903:Pituitary Gland, Anterior / Q000187:drug effects / Q000378:metabolism*; D011388:Prolactin / Q000378:metabolism*; D013552:Swine / Q000378:metabolism*; D013973:Thyrotropin-Releasing Hormone / Q000494:pharmacology / Q000502:physiology
D001971:Bromocriptine; D013973:Thyrotropin-Releasing Hormone; D011388:Prolactin; D004298:Dopamine