Effect of L-dopa on milk ejection and prolactin release in lactating rats.
The effect of L-DOPA on milk ejection and on prolactin release during 30 min of suckling was studied in lactating rats. Various doses of L-DOPA (1-25, 2-5, 5 and 10 mg/100 g body wt) were injected i.p. 30 min before the suckling period. Control rats were injected with 0-9% NaCl solution only. An inhibition of milk ejection proportional to the dose of drug administered was obtained. The dose of 10 mg completely blocked milk ejection but 1-25 mg had no effect. A normal milk-ejection response was obtained with a small dose of oxytocin injected immediately before nursing into mothers treated with 10 mg L-DOPA, indicating that the blocking effect was not due to a lack of mammary gland response. In control mothers, serum prolactin levels increased from 67-2 +/- 25-9 (S.E.M.) to 950-3 +/- 118-7 ng/ml after a 30 min suckling period. L-DOPA (5 and 10 mg) prevented the release of prolactin induced by suckling, but 1-25 and 2-5 mg L-DOPA had no effect. The results indicate that oxytocin and prolactin release induced by suckling in lactating rats is inhibited by an increase of catecholamines at the hypothalamic-hypophysial axis.
D000818:Animals; D005260:Female; D007774:Lactation / Q000187:drug effects*; D007980:Levodopa / Q000008:administration & dosage / Q000494:pharmacology*; D008893:Milk Ejection / Q000187:drug effects*; D010121:Oxytocin / Q000378:metabolism; D011247:Pregnancy; D011388:Prolactin / Q000097:blood / Q000378:metabolism*; D051381:Rats; D013391:Sucking Behavior
D007980:Levodopa; D010121:Oxytocin; D011388:Prolactin