Goshima Y, Nakamura S, Ohno K, Misu Y
Department of Pharmacology, Yokohama City University School of Medicine, Japan.
Neurosci Lett. 1991 Aug 19;129(2):214-6. doi: 10.1016/0304-3940(91)90464-5.
Interactions between (-)-isoproterenol and DOPA on the release of endogenous noradrenaline (NA) evoked by electrical field stimulation (2 Hz, alternative polarity) were studied in rat superfused hypothalamic slices in the presence of 3-hydroxybenzylhydrazine, an inhibitor of L-aromatic amino acid decarboxylase, and cocaine. Isoproterenol (0.3-3 nM) facilitated the NA release in a concentration-dependent manner, while 10 pM L-DOPA alone produced no effect. This facilitation at 0.3-3 nM was potentiated by 20-70% by simultaneously applied 10 pM L-DOPA but that at 3 nM was not modified by 10 pM D-DOPA. This potentiation of the isoproterenol (3 nM)-induced facilitation of the NA release was concentration-dependent at 1-10 pM of L-DOPA. L-DOPA methyl ester (1 nM) antagonized the L-DOPA (10 pM)-induced potentiation of the facilitation of the NA release by 3 nM isoproterenol to a level of the facilitation by isoproterenol alone, whereas 10 nM (-) propranolol antagonized both the facilitation by isoproterenol alone and its potentiation by L-DOPA to a control level. Picomolar concentrations of L-DOPA stereoselectively act on a recognition site for itself, and then potentiate activities of presynaptic beta-adrenoceptors to facilitate the NA release from rat hypothalamic slices.
在存在L-芳香族氨基酸脱羧酶抑制剂3-羟基苄基肼和可卡因的情况下，在大鼠下丘脑灌流切片中研究了（-）-异丙肾上腺素与多巴对电场刺激（2Hz，交替极性）诱发的内源性去甲肾上腺素（NA）释放的相互作用。异丙肾上腺素（0.3-3nM）以浓度依赖性方式促进NA释放，而单独使用10pM左旋多巴则无作用。同时应用10pM左旋多巴可使0.3-3nM时的这种促进作用增强20-70%，但3nM时的促进作用不受10pM右旋多巴的影响。左旋多巴（1-10pM）对异丙肾上腺素（3nM）诱导的NA释放促进作用的这种增强呈浓度依赖性。左旋多巴甲酯（1nM）将左旋多巴（10pM）诱导的3nM异丙肾上腺素对NA释放促进作用的增强拮抗至单独异丙肾上腺素促进作用的水平，而10nM（-）普萘洛尔将单独异丙肾上腺素的促进作用及其被左旋多巴的增强作用均拮抗至对照水平。皮摩尔浓度的左旋多巴对其自身的识别位点具有立体选择性作用，然后增强突触前β-肾上腺素能受体的活性，以促进大鼠下丘脑切片中NA的释放。
