Cyclic variation of oxytocin in the blood of pituitary portal vessels of rats

D. K. Sarkar, D. M. Gibbs

Research output: Contribution to journalArticlepeer-review

84 Scopus citations


The release of oxytocin (OT) into pituitary portal blood during the estrous cycle was studied in female rats under Althesin anesthesia. On each afternoon of the 4-day estrous cycle, animals were anesthetized with Althesin, and pituitary portal blood samples were collected. The concentration of OT in portal plasma collected between 14.00 and 16.00 h of proestrus (1,079 ± 185 pg/ml) was significantly higher than that at any other time studied. There were no appreciable differences between the mean OT concentration on the days of estrus (198 ± 29 pg/ml), metestrus (283 ± 55 pg/ml), and diestrus (267 ± 49 pg/ml). The concentration of OT in pituitary portal plasma was also greater than that in blood withdrawn from the external jugular vein (<41-67 pg/ml). Comparison of the portal plasma OT with peripheral plasma prolactin in Althesin-anesthetized rats indicated an association between the release of these hormones during the estrous cycle.

Original languageEnglish (US)
Pages (from-to)481-483
Number of pages3
Issue number5
StatePublished - 1984
Externally publishedYes

ASJC Scopus subject areas

  • Endocrinology, Diabetes and Metabolism
  • Endocrinology
  • Endocrine and Autonomic Systems
  • Cellular and Molecular Neuroscience


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