Timmerman W, Deinum M E, Poelman R T, Westerink B H, Schuiling G A
Department of Obstetrics and Gynaecology, University of Groningen, The Netherlands.
Brain Res. 1994 Sep 19;657(1-2):275-80. doi: 10.1016/0006-8993(94)90977-6.
The TIDA neurons, which constitute part of the arcuate nucleus-ME complex, play an important inhibitory role in the regulation of the PRL secretion from the adenohypophysis. To simultaneously study the release of DA from the TIDA neurons and the PRL secretion from the adenohypophysis in awake rats, a microdialysis probe was implanted into the MBH together with a permanent heartcannula in male rats. The extracellular levels of DA in the MBH as measured by microdialysis decreased to 25% of basal values after local infusion of TTX (1 mumol/l), indicating that the released DA was directly derived from neuronal activity. DOPAC levels were not affected. This local infusion of TTX into the MBH induced parallel to the immediate decrease in DA levels, a profound increase in PRL concentration in the blood (from 10 to 55 ng/PRL-RP-2/ml) directly after infusion. Thus, the area in which the dialysis probe was inserted indeed included the DA-ergic neurons that regulate the PRL secretion. Evidence for a functional re-uptake system in the MBH was obtained by local infusion of the re-uptake inhibitor nomifensine (5 mumol/l) which induced an increase in DA release to 350% of basal values, without affecting the DOPAC levels. In spite of this increase in DA levels, the PRL concentration in the blood was not affected. In pseudopregnant female rats, relatively high levels of extracellular DA in the MBH were obtained during the interphase during which the PRL levels are low, while lower DA levels were apparent during the phase the spontaneous nocturnal PRL surge normally appears. Taken together, the approach presented in this study, i.e. the simultaneous measurements of DA in the MBH and PRL in the blood, establishes an advanced method enabling studies on the DA-PRL interactions in awake animals.
促甲状腺激素抑制激素（TIDA）神经元是弓状核 - 正中隆起复合体的一部分，在腺垂体催乳素（PRL）分泌的调节中起重要的抑制作用。为了同时研究清醒大鼠中TIDA神经元释放多巴胺（DA）以及腺垂体分泌PRL的情况，将一个微透析探针与一个永久性心脏插管一起植入雄性大鼠的中脑基底部（MBH）。通过微透析测量发现，在局部注入河豚毒素（TTX，1 μmol/L）后，MBH中细胞外DA水平降至基础值的25%，这表明释放的DA直接来源于神经元活动。3,4 - 二羟基苯乙酸（DOPAC）水平未受影响。在MBH局部注入TTX后，与DA水平立即下降同时发生的是，注入后血液中PRL浓度显著升高（从10至55 ng/PRL - RP - 2/ml）。因此，插入透析探针的区域确实包含调节PRL分泌的DA能神经元。通过局部注入再摄取抑制剂诺米芬辛（5 μmol/L）获得了MBH中存在功能性再摄取系统的证据，这导致DA释放增加至基础值的350%，而不影响DOPAC水平。尽管DA水平有所升高，但血液中的PRL浓度未受影响。在假孕雌性大鼠中，在PRL水平较低的间期，MBH中细胞外DA水平相对较高，而在通常出现自发性夜间PRL激增的阶段，DA水平较低。综上所述，本研究中提出的方法，即同时测量MBH中的DA和血液中的PRL，建立了一种先进的方法，能够用于研究清醒动物中DA - PRL的相互作用。
