Effect of haloperidol, suckling, oxytocin and hand milking on plasma relaxin and prolactin concentrations in cyclic and lactating pigs.
Prolactin secretion was stimulated in 5 cyclic gilts during the luteal phase (Day 10-13) with 5 mg haloperidol given i.v. Stimulation of prolactin secretion was also attempted by inducing milk let-down by suckling (4 sows), or by the injection of 1 mg oxytocin i.v. followed by hand milking (3 sows). Plasma prolactin concentrations increased significantly 1-2 h after haloperidol injection, and in 3 of 4 sows during suckling (P = 0.001); plasma relaxin concentrations did not change significantly at these times. No change was observed in plasma prolactin or relaxin concentrations at 15 min or 1-2 h after oxytocin injection and hand milking. Plasma relaxin concentrations ranged from below the sensitivity of the assay (100 pg/ml) to 450 pg/ml in lactating sows and from 100 to 2000 pg/ml in cyclic gilts. The results suggest that in cyclic gilts treated in the luteal phase with a dopaminergic receptor blocker, and in lactating sows during suckling, elevations in plasma prolactin concentrations were not accompanied, during the same period, by detectable changes in relaxin concentrations.
D000818:Animals; D004971:Estrus; D005260:Female; D006220:Haloperidol / Q000494:pharmacology*; D007774:Lactation; D008893:Milk Ejection; D010121:Oxytocin / Q000494:pharmacology*; D011247:Pregnancy; D011388:Prolactin / Q000097:blood*; D012065:Relaxin / Q000097:blood*; D013552:Swine
D010121:Oxytocin; D011388:Prolactin; D012065:Relaxin; D006220:Haloperidol