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Differential sensitivity of prolactin release to dopamine and thyrotrophin-releasing hormone in intact and pituitary stalk-sectioned rhesus monkeys.
J Endocrinol. 1980 Mar; 84(3):479-87.JE

Abstract

The effects of dopamine and thyrotrophin-releasing hormone (TRH) on prolactin release was studied in 14 intact and six pituitary stalk-sectioned (SS) female rhesus monkeys (Macaca mulatta). Baseline prolactin values were ninefold higher in SS animals (149+/-16 ng/ml) than in intact animals (16+/-1 ng/ml). Prolactin release after intravenous administration of TRH in doses of 0, 125, 250, 500 and 1000 ng revealed that SS monkeys were more sensitive to the prolactin-releasing activity of this tripeptide than were intact animals. A significant (P less than 0.05) increment in serum prolactin was observed in SS animals after injection of 125 ng TRH whereas 250 ng was required to raise prolactin levels in the circulation of intact animals significantly (P less than 0.05). Furthermore, at each comparable dose level of TRH, the increment in serum prolactin was distinctly greater in SS animals than in intact monkeys. Infusion of dopamine at the rate of 10 microgram/kg body weight per min significantly (P less than 0.05) lowered prolactin levels within 60 min in intact animals and no further decline was observed with 20 or 40 microgram dopamine. Serum prolactin concentrations were not affected by saline infusion or by 5 microgram dopamine. Infusion of dopamine at the rate of 10 microgram/kg body wt per min also resulted in significant (P less than 0.01) suppression of serum prolactin in SS animals. This prolactin decrease was apparent within 40 min. Prolactin release after 500 ng TRH was less in these dopamine-treated SS monkeys than after an infusion of saline. Higher doses of dopamine (20 and 40 microgram) did not cause a further decrease in basal serum prolactin concentrations, but these two dopamine treatments blocked the increase in prolactin elicited by 500 ng TRH. The results suggest that the removal of hypothalamic influence, possibly related to the effects of dopamine, renders the pituitary gland more sensitive to the prolactin-releasing action of TRH.

Authors

No affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, U.S. Gov't, P.H.S.

Language

eng

PubMed ID

6771353

Citation

Norman, R L., et al. "Differential Sensitivity of Prolactin Release to Dopamine and Thyrotrophin-releasing Hormone in Intact and Pituitary Stalk-sectioned Rhesus Monkeys." The Journal of Endocrinology, vol. 84, no. 3, 1980, pp. 479-87.
Norman RL, Quadri SK, Spies HG. Differential sensitivity of prolactin release to dopamine and thyrotrophin-releasing hormone in intact and pituitary stalk-sectioned rhesus monkeys. J Endocrinol. 1980;84(3):479-87.
Norman, R. L., Quadri, S. K., & Spies, H. G. (1980). Differential sensitivity of prolactin release to dopamine and thyrotrophin-releasing hormone in intact and pituitary stalk-sectioned rhesus monkeys. The Journal of Endocrinology, 84(3), 479-87.
Norman RL, Quadri SK, Spies HG. Differential Sensitivity of Prolactin Release to Dopamine and Thyrotrophin-releasing Hormone in Intact and Pituitary Stalk-sectioned Rhesus Monkeys. J Endocrinol. 1980;84(3):479-87. PubMed PMID: 6771353.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Differential sensitivity of prolactin release to dopamine and thyrotrophin-releasing hormone in intact and pituitary stalk-sectioned rhesus monkeys. AU - Norman,R L, AU - Quadri,S K, AU - Spies,H G, PY - 1980/3/1/pubmed PY - 1980/3/1/medline PY - 1980/3/1/entrez SP - 479 EP - 87 JF - The Journal of endocrinology JO - J Endocrinol VL - 84 IS - 3 N2 - The effects of dopamine and thyrotrophin-releasing hormone (TRH) on prolactin release was studied in 14 intact and six pituitary stalk-sectioned (SS) female rhesus monkeys (Macaca mulatta). Baseline prolactin values were ninefold higher in SS animals (149+/-16 ng/ml) than in intact animals (16+/-1 ng/ml). Prolactin release after intravenous administration of TRH in doses of 0, 125, 250, 500 and 1000 ng revealed that SS monkeys were more sensitive to the prolactin-releasing activity of this tripeptide than were intact animals. A significant (P less than 0.05) increment in serum prolactin was observed in SS animals after injection of 125 ng TRH whereas 250 ng was required to raise prolactin levels in the circulation of intact animals significantly (P less than 0.05). Furthermore, at each comparable dose level of TRH, the increment in serum prolactin was distinctly greater in SS animals than in intact monkeys. Infusion of dopamine at the rate of 10 microgram/kg body weight per min significantly (P less than 0.05) lowered prolactin levels within 60 min in intact animals and no further decline was observed with 20 or 40 microgram dopamine. Serum prolactin concentrations were not affected by saline infusion or by 5 microgram dopamine. Infusion of dopamine at the rate of 10 microgram/kg body wt per min also resulted in significant (P less than 0.01) suppression of serum prolactin in SS animals. This prolactin decrease was apparent within 40 min. Prolactin release after 500 ng TRH was less in these dopamine-treated SS monkeys than after an infusion of saline. Higher doses of dopamine (20 and 40 microgram) did not cause a further decrease in basal serum prolactin concentrations, but these two dopamine treatments blocked the increase in prolactin elicited by 500 ng TRH. The results suggest that the removal of hypothalamic influence, possibly related to the effects of dopamine, renders the pituitary gland more sensitive to the prolactin-releasing action of TRH. SN - 0022-0795 UR - https://www.unboundmedicine.com/medline/citation/6771353/Differential_sensitivity_of_prolactin_release_to_dopamine_and_thyrotrophin_releasing_hormone_in_intact_and_pituitary_stalk_sectioned_rhesus_monkeys_ L2 - https://joe.bioscientifica.com/doi/10.1677/joe.0.0840479 DB - PRIME DP - Unbound Medicine ER -