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Biology of Reproduction, Vol 21, 1067-1072, Copyright © 1979 by Society for the Study of Reproduction
1 Department of Physiology,
Wayne State University School of Medicine,
Detroit, Michigan 48201 The role of the pineal gland in the regulation of the daily afternoon surge of plasma prolactin
in the ovariectomized, polyestradiol phosphate (PEP) treated rat was investigated. The effect of
olfactory bulbectomy and/or short photoperiod (2L:22D), two procedures which may enhance
pineal activity, was also examined. Control rats given PEP and maintained on 14L:10D cycles with
the lights on from 0600-2000 h had afternoon surges of plasma prolactin with maximum levels
between 1500-1900 h; the levels were similar whether the animals were sampled by decapitation
or through catheters if the catheter extension was connected at 0700 h. However, if the catheter
extension was connected at 1500 h, prolactin secretion at 1700 h was significantly inhibited.
Pinealectomy or olfactory bulbectomy at the time of ovariectomy had no effect on the prolactin
surges of ovariectomized, PEP treated rats whether they were maintained on 14L:10D or 2L:22D
cycles. Control ovariectomized, PEP treated rats maintained on the 2L:22D photoperiod with the
lights on from 1200-1400 h had prolactin surges similar to those in rats maintained on the standard 14L:10D photoperiod, but the maximum levels occurred between 1700-2100 h. It is concluded that the pineal gland and olfactory bulbs are not involved in the regulation of the afternoon
prolactin surge of ovariectomized, estrogen treated rats. It is also concluded that short photoperiod
has no effect on the magnitude of the surge.
Note:
ACKNOWLEDGMENTS
The authors appreciate the excellent technical
assistance of Mrs. Cynthia Van De Walle and Mrs.
Mee-Ling Chin. Appreciation is also extended to
NIAMDD for providing the rat prolactin for standards
and iodination.
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