Gopalan C, Tian Y, Moore K E, Lookingland K J
Department of Pharmacology and Toxicology, Michigan State University, East Lansing 48824.
Neuroendocrinology. 1993 Sep;58(3):287-93. doi: 10.1159/000126552.
The purpose of the present study was to examine the effects of galanin on the basal and stimulated activity of tuberoinfundibular dopaminergic (TIDA) neurons in male and female rats. TIDA neuronal activity was estimated by measuring dopamine (DA) synthesis [accumulation of 3,4-dihydroxyphenylalanine(DOPA) after administration of a decarboxylase inhibitor] and metabolism [ratio of 3,4-dihydroxyphenylacetic acid (DOPAC) to DA concentrations] in terminals of these neurons in the median eminence. Central administration of galanin (2 micrograms/rat, i.c.v.) produced a rapid (by 15 min) increase in plasma prolactin concentrations, but had no effect on the ratio of DOPAC to DA in the median eminence of either male or female rats. In contrast, galanin decreased the ratio of DOPAC to DA in the median eminence of both male and female rats whose TIDA neuronal activity was stimulated following administration of the DA antagonist haloperidol (1 mg/kg, s.c., 12 h). The galanin receptor antagonist galanin-(1-13)-bradykinin-(2-9)-amide had no effect on the accumulation of DOPA in the median eminence of male rats per se, but blocked the inhibitory effects of either exogenous or endogenous galanin on median eminence DOPA accumulation in haloperidol-treated rats. These results indicate that in both male and female rats, galanin-induced activation of prolactin secretion is not mediated by changes in tonic inhibition of hormone release by TIDA neurons, and that TIDA neurons are responsive to the inhibitory effects of galanin only under activated conditions.
本研究的目的是检测甘丙肽对雄性和雌性大鼠结节漏斗多巴胺能（TIDA）神经元基础活性和刺激活性的影响。通过测量这些神经元在正中隆起终末的多巴胺（DA）合成[给予脱羧酶抑制剂后3,4-二羟基苯丙氨酸（DOPA）的积累]和代谢[3,4-二羟基苯乙酸（DOPAC）与DA浓度的比值]来评估TIDA神经元活性。中枢给予甘丙肽（2微克/大鼠，脑室内注射）可使血浆催乳素浓度迅速（15分钟内）升高，但对雄性或雌性大鼠正中隆起处DOPAC与DA的比值均无影响。相比之下，在给予DA拮抗剂氟哌啶醇（1毫克/千克皮下注射，12小时）后刺激TIDA神经元活性的雄性和雌性大鼠中，甘丙肽降低了正中隆起处DOPAC与DA的比值。甘丙肽受体拮抗剂甘丙肽-（1-13）-缓激肽-（2-9）-酰胺本身对雄性大鼠正中隆起处DOPA的积累没有影响，但可阻断外源性或内源性甘丙肽对氟哌啶醇处理大鼠正中隆起处DOPA积累的抑制作用。这些结果表明，在雄性和雌性大鼠中，甘丙肽诱导的催乳素分泌激活不是由TIDA神经元对激素释放的紧张性抑制变化介导的，并且TIDA神经元仅在激活状态下对甘丙肽的抑制作用有反应。
