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 The concentration of OT in pituitary portal plasma was also greater than that in blood withdrawn from the external jugular vein (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.
ASJC Scopus subject areas
- Endocrinology, Diabetes and Metabolism
- Endocrine and Autonomic Systems
- Cellular and Molecular Neuroscience