Abstract
Summary
1. The quantity of milk secured by litters of lactating rats treated with ergotamine 10 minutes before nursing was significantly less than that obtained by control offspring. Oxytocin administered before or after ergotamine restored normal milk letdown. 2. Topical application of ergotamine to living rat mammary tissue resulted in arteriole constriction but did not interfere with normal myoepithelial contraction induced by oxytocin. 3. Results indicate ergotamine does not inhibit milk let-down through vasoconstriction of mammary blood vessels thus prohibiting access of oxytocin to effector myoepithelium. Rather, a competition between ergotamine and oxytocin for the effector tissue or a neural block inhibiting release of oxytocin by posterior pituitary gland seem more probable.
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