Norman R L, Quadri S K, Spies H G
J Endocrinol. 1980 Mar;84(3):479-87. doi: 10.1677/joe.0.0840479.
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.
在14只未处理和6只垂体柄横断（SS）的雌性恒河猴（猕猴）中研究了多巴胺和促甲状腺激素释放激素（TRH）对催乳素释放的影响。SS动物的催乳素基线值（149±16 ng/ml）比未处理动物（16±1 ng/ml）高9倍。静脉注射剂量为0、125、250、500和1000 ng的TRH后催乳素释放情况显示，SS猴对这种三肽的催乳素释放活性比未处理动物更敏感。注射125 ng TRH后，SS动物血清催乳素显著升高（P<0.05），而未处理动物循环中催乳素水平显著升高（P<0.05）则需要注射250 ng。此外，在每个可比的TRH剂量水平下，SS动物血清催乳素的升高明显大于未处理的猴子。以每分钟10微克/千克体重的速率输注多巴胺在60分钟内显著降低了未处理动物的催乳素水平（P<0.05），输注20或40微克多巴胺时未观察到进一步下降。生理盐水输注或5微克多巴胺对血清催乳素浓度无影响。以每分钟10微克/千克体重的速率输注多巴胺也导致SS动物血清催乳素显著抑制（P<0.01）。这种催乳素降低在40分钟内明显。在这些多巴胺处理的SS猴中，500 ng TRH后的催乳素释放比输注生理盐水后少。更高剂量的多巴胺（20和40微克）未导致基础血清催乳素浓度进一步降低，但这两种多巴胺处理阻断了500 ng TRH引起的催乳素升高。结果表明，去除下丘脑的影响，可能与多巴胺的作用有关，使垂体对TRH的催乳素释放作用更敏感。
