Brief decreases in dopamine result in surges of prolactin secretion in monkeys
Frawley, L.S.; Neill, J.D.
American Journal of Physiology 247(6 Pt 1): E778-E780
1984
ISSN/ISBN: 0002-9513 PMID: 6507613 Document Number: 224206
The amount of dopamine in hypophysial stalk blood was sufficient to account for tonic hypothalamic inhibition of prolactin secretion in rhesus monkeys. The effect on prolactin secretion of decreases in dopamine was studied. When hypophysial stalk-transected, estrogen-treated monkeys were infused with dopamine at a rate (0.1 .mu.g/kg per min) to achieve peripheral plasma concentrations similar to those previously measured in stalk blood, their elevated serum prolactin levels fell to baseline (from 47.6 .+-. 4.8 to 9.7 .+-. 2.7 ng/ml, mean .+-. SE, n = 4). Brief interruptions of the dopamine infusions lasting for 2.5, 5.0, or 7.5 min evoked rapid increases in serum prolactin concentrations to (27.5 .+-. 8.3, 52.9 .+-. 3.6 and 58.9 .+-. 8.1 ng/ml, respectively, at 10 min). Maximal prolactin level were attained within 10-20 min after dopamine removal and serum prolactin remained elevated for an additional 35-150 min. Uninterrupted dopamine infusions of stalk-transected, estrogen-treated monkeys (n = 3) led to continuously suppressed prolactin values. Brief decreases in dopamine lead to major increases in prolactin secretion. Thus, if a brief decrease in hypothalamic dopamine secretion occurs after a suckling stimulus in monkeys, as it does in rats, a decrease in dopamine secretion alone may account, in part, for suckling-induced prolactin secretion in monkeys.