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Dissociation of prolactin secretion from tuberoinfundibular dopamine activity in late pregnant rats.
Endocrinology. 2001 Jun; 142(6):2719-24.E

Abstract

This study investigated whether the PRL surge that precedes parturition is accompanied by a decrease in activity of hypothalamic tuberoinfundibular dopamine (TIDA) neurons, as occurs during the PRL surges of early pregnancy. Serial blood samples were collected at regular intervals during early and late pregnancy via chronic indwelling jugular cannulae, and concentrations of plasma PRL were determined by RIA. In addition, pregnant rats were killed at either 1200 and 0300 h on different days throughout pregnancy. Levels of TIDA neuronal activity were estimated using concentrations of 3,4-dihydroxyphenylacetic acid (DOPAC) in the median eminence as an index of dopamine metabolism. During early pregnancy, plasma PRL concentrations showed characteristic diurnal and nocturnal surges peaking at 1700 and 0300 h, respectively, whereas during late pregnancy, there was a broad nocturnal surge throughout the night preceding parturition. During early pregnancy, DOPAC was elevated at 1200 h, associated with suppressed plasma PRL, whereas at 0300 h, during the nocturnal PRL surge, DOPAC was significantly reduced (P < 0.05). On the last day of pregnancy DOPAC levels were significantly reduced at both 1200 and 0300 h compared with those at 1200 h in early pregnancy regardless of the PRL concentration. This experiment was repeated with additional groups to further characterize the timing of the fall in TIDA activity during late pregnancy. DOPAC concentrations were elevated throughout the second half of pregnancy, then fell significantly between 0300-1200 h on day 21, approximately 36 h before parturition. As in the previous experiment, the timing of changes in DOPAC concentrations in the median eminence was dissociated from the antepartum PRL surge. These data indicate that the regulation of PRL secretion during late pregnancy is different from that of early pregnancy. Despite the prolonged reduction in activity of TIDA neurons during late pregnancy, PRL secretion still occurs as a nocturnal surge, suggesting that dopamine is not the only regulator of PRL secretion at this time.

Authors+Show Affiliations

Department of Anatomy and Structural Biology and Neuroscience Research Center, University of Otago School of Medical Sciences, Dunedin, New Zealand.No affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

11356724

Citation

Andrews, Z B., et al. "Dissociation of Prolactin Secretion From Tuberoinfundibular Dopamine Activity in Late Pregnant Rats." Endocrinology, vol. 142, no. 6, 2001, pp. 2719-24.
Andrews ZB, Kokay IC, Grattan DR. Dissociation of prolactin secretion from tuberoinfundibular dopamine activity in late pregnant rats. Endocrinology. 2001;142(6):2719-24.
Andrews, Z. B., Kokay, I. C., & Grattan, D. R. (2001). Dissociation of prolactin secretion from tuberoinfundibular dopamine activity in late pregnant rats. Endocrinology, 142(6), 2719-24.
Andrews ZB, Kokay IC, Grattan DR. Dissociation of Prolactin Secretion From Tuberoinfundibular Dopamine Activity in Late Pregnant Rats. Endocrinology. 2001;142(6):2719-24. PubMed PMID: 11356724.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Dissociation of prolactin secretion from tuberoinfundibular dopamine activity in late pregnant rats. AU - Andrews,Z B, AU - Kokay,I C, AU - Grattan,D R, PY - 2001/5/18/pubmed PY - 2001/6/22/medline PY - 2001/5/18/entrez SP - 2719 EP - 24 JF - Endocrinology JO - Endocrinology VL - 142 IS - 6 N2 - This study investigated whether the PRL surge that precedes parturition is accompanied by a decrease in activity of hypothalamic tuberoinfundibular dopamine (TIDA) neurons, as occurs during the PRL surges of early pregnancy. Serial blood samples were collected at regular intervals during early and late pregnancy via chronic indwelling jugular cannulae, and concentrations of plasma PRL were determined by RIA. In addition, pregnant rats were killed at either 1200 and 0300 h on different days throughout pregnancy. Levels of TIDA neuronal activity were estimated using concentrations of 3,4-dihydroxyphenylacetic acid (DOPAC) in the median eminence as an index of dopamine metabolism. During early pregnancy, plasma PRL concentrations showed characteristic diurnal and nocturnal surges peaking at 1700 and 0300 h, respectively, whereas during late pregnancy, there was a broad nocturnal surge throughout the night preceding parturition. During early pregnancy, DOPAC was elevated at 1200 h, associated with suppressed plasma PRL, whereas at 0300 h, during the nocturnal PRL surge, DOPAC was significantly reduced (P < 0.05). On the last day of pregnancy DOPAC levels were significantly reduced at both 1200 and 0300 h compared with those at 1200 h in early pregnancy regardless of the PRL concentration. This experiment was repeated with additional groups to further characterize the timing of the fall in TIDA activity during late pregnancy. DOPAC concentrations were elevated throughout the second half of pregnancy, then fell significantly between 0300-1200 h on day 21, approximately 36 h before parturition. As in the previous experiment, the timing of changes in DOPAC concentrations in the median eminence was dissociated from the antepartum PRL surge. These data indicate that the regulation of PRL secretion during late pregnancy is different from that of early pregnancy. Despite the prolonged reduction in activity of TIDA neurons during late pregnancy, PRL secretion still occurs as a nocturnal surge, suggesting that dopamine is not the only regulator of PRL secretion at this time. SN - 0013-7227 UR - https://www.unboundmedicine.com/medline/citation/11356724/Dissociation_of_prolactin_secretion_from_tuberoinfundibular_dopamine_activity_in_late_pregnant_rats_ L2 - https://academic.oup.com/endo/article-lookup/doi/10.1210/endo.142.6.8196 DB - PRIME DP - Unbound Medicine ER -