On the mechanism of lactational anovulation in the rhesus monkey

Tamás Ördög, Ming Dao Chen, Kevin T. O'Byrne, Jason R. Goldsmith, Martin A. Connaughton, Julane Hotchkiss, Ernst Knobil

Research output: Contribution to journalArticlepeer-review

35 Scopus citations

Abstract

The relative roles of infant suckling and of maternal prolactin (PRL) secretion in lactational anovulation were studied in ovary-intact and ovariectomized rhesus monkeys nursing young that had been removed from their natural mothers. Hypothalamic gonadotropin-releasing hormone (GnRH) pulse generator activity was monitored electrophysiologically in freely behaving animals by radiotelemetry. Serum luteinizing hormone, PRL, estradiol, and progesterone were also measured. Suckling inhibited GnRH pulse generator activity and ovarian cyclicity in all ovary-intact females but had no such effect on the pulse generator in long-term ovariectomized animals. When PRL secretion was suppressed by daily bromocriptine administration, GnRH pulse generator activity remained significantly inhibited and ovulation was prevented in four monkeys (6 trials), whereas in two females (6 trials) a rapid increase in pulse generator frequency and the resumption of ovarian cyclicity were observed although suckling activity was maintained. One monkey displayed both response types. Although these results indicate that suckling per se is able to restrain GnRH pulse generator activity in the absence of PRL, they also suggest that the relative importance of these determinants is variable depending on factors that remain to be determined. The present study also confirms the permissive role of the ovary in the lactational suppression of GnRH pulse generator activity.

Original languageEnglish (US)
Pages (from-to)E665-E676
JournalAmerican Journal of Physiology - Endocrinology and Metabolism
Volume274
Issue number4 37-4
DOIs
StatePublished - Apr 1998

Keywords

  • Bromocriptine
  • Gonadotropin-releasing hormone pulse generator
  • Multiunit electrical activity volley
  • Pregnancy
  • Prolactin

ASJC Scopus subject areas

  • Endocrinology, Diabetes and Metabolism
  • Physiology
  • Physiology (medical)

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