DeMaria J E, Lerant A A, Freeman M E
Program in Neuroscience, Department of Biological Science, Florida State University, Tallahassee, FL 32306-4340, USA.
Brain Res. 1999 Aug 7;837(1-2):236-41. doi: 10.1016/s0006-8993(99)01667-4.
Prior studies suggest that prolactin (PRL) stimulates release of dopamine (DA) from tuberoinfundibular dopaminergic (TIDA) neurons. In the present study, the time course over which PRL exerts its effects on all three populations of neuroendocrine dopaminergic (DAergic) neuron populations [TIDA, tuberohypophyseal (THDA) and periventricular-hypophyseal (PHDA)] was determined. Ten days following ovariectomy (OVX), groups of female rats were injected either with 15 microg of ovine PRL (oPRL) or saline at 0900 h. Rats were decapitated every 30 min from 0830 h-1100 h and hourly from 1200 h-1500 h. Trunk blood was assayed for rat PRL (rPRL) and oPRL using species-specific radioimmunoassays (RIAs). The concentration of DA and 3,4-dihydroxyphenylacetic acid (DOPAC) in the median eminence (ME), as well as the anterior (AL), intermediate (IL) and neural (NL) lobes of the pituitary gland were determined by HPLC-EC. The concentration of rPRL in oPRL-treated animals, compared to saline-treated animals, was diminished by 1000 h and again between 1200 h-1500 h. DOPAC/DA ratio, an indicator of dopaminergic neuronal activity, increased spontaneously in the ME, IL, and NL during the afternoon in OVX rats. In animals injected with oPRL at 0900 h, the DOPAC/DA ratio increased in the ME, IL and NL within 1 h. Moreover, a secondary increase in the DOPAC/DA ratio in the IL and NL occurred during the afternoon in oPRL-treated rats. However, the second increase of DA turnover present in the ME of control animals never occurred in oPRL-treated animals. Furthermore, there were two increases in the concentration of DA in the AL: the first coincided with the increased turnover of DA in all three terminal areas and the second with increased DA turnover in the IL and NL. These data suggest that all three populations of hypothalamic neuroendocrine DAergic neurons are activated by PRL and that PHDA/THDA neurons have a second 'delayed' activation.
先前的研究表明，催乳素（PRL）可刺激结节漏斗多巴胺能（TIDA）神经元释放多巴胺（DA）。在本研究中，确定了PRL对所有三种神经内分泌多巴胺能（DAergic）神经元群体[即TIDA、结节垂体（THDA）和室周垂体（PHDA）]发挥作用的时间进程。卵巢切除（OVX）10天后，在上午9点给雌性大鼠注射15微克羊催乳素（oPRL）或生理盐水。从上午8点30分至11点，每30分钟对大鼠进行断头处理；从中午12点至下午3点，每小时断头处理一次。使用物种特异性放射免疫分析（RIA）法测定大鼠躯干血液中的大鼠PRL（rPRL）和oPRL。通过高效液相色谱 - 电化学检测法（HPLC - EC）测定正中隆起（ME）以及垂体前叶（AL）、中间叶（IL）和神经叶（NL）中DA和3,4 - 二羟基苯乙酸（DOPAC）的浓度。与生理盐水处理的动物相比，接受oPRL处理的动物体内rPRL浓度在10点时降低，并且在中午12点至下午3点之间再次降低。DOPAC/DA比值是多巴胺能神经元活性的指标，在下午时段，OVX大鼠的ME、IL和NL中该比值自发升高。在上午9点注射oPRL的动物中，ME、IL和NL中的DOPAC/DA比值在1小时内升高。此外，在接受oPRL处理的大鼠下午时段，IL和NL中的DOPAC/DA比值出现二次升高。然而，对照动物ME中出现的DA周转率二次升高在接受oPRL处理的动物中从未出现。此外，AL中DA浓度有两次升高：第一次与所有三个终末区域中DA周转率升高同时出现，第二次与IL和NL中DA周转率升高同时出现。这些数据表明，下丘脑神经内分泌DAergic神经元的所有三个群体均被PRL激活，并且PHDA/THDA神经元具有第二次“延迟”激活。
