Abstract
Summary
Nonlactating, nonpregnant Holstein cows were used to examine the effects of an im injection of reserpine. A 5-mg reserpine injection resulted in a rapid (within 0.5 hr) and sustained (at least 24 hr) elevation of serum prolactin. Peak prolactin levels (283 ng/ml) occurred 3 hr postinjection. Serum glucocorticoid and growth hormone concentrations were unaffected by reserpine injection. Two sequential injections of 5 mg of reserpine given at 48-hr intervals gave nearly identical prolactin responses. The prolactin response to reserpine was dose dependent with 1 mg giving approximately 39.5% of the response obtained with 5 mg of reserpine.
The authors appreciate the assistance of C. J. Wil-cox, Dairy Science Department, University of Florida, with analysis of the mixed-model factorial design.
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