Tyce G M, Rorie D K
Life Sci. 1985 Dec 23;37(25):2439-48. doi: 10.1016/0024-3205(85)90112-2.
Conjugation (presumably with sulfate) is a demonstrable metabolic pathway for 3, 4-dihydroxyphenylethylamine (dopamine, DA) in brain. Studies were done to determine whether conjugation becomes of increased significance in the presence of precursors of DA. The effects of 3, 4-dihydroxyphenylalanine (L-DOPA) and L-tyrosine on the efflux of free and conjugated DA, 3, 4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid from slices from striatum in rats were studied under quiescent conditions and during release evoked by 40 mM K+ or by 5 X 10(-5) M phenylethylamine (PEA). Conjugated DA was present in the basal efflux from striatal slices and the amounts present were increased during evoked release. More conjugated DA was present in superfusate during K+-evoked release than during PEA-evoked release. L-Tyrosine (5 X 10(-4) M or 5 X 10(-5) M) had little effect on the efflux of conjugated DA, but decreased the amounts of free DA released by PEA, and attenuated the increase in DOPAC that occurred during K+-evoked release of transmitter. L-DOPA (5 X 10(-5) M) increased the formation of conjugated DA, but to a lesser extent than that of free DA or of DOPAC. Thus even after the addition of precursors, conjugation remains a minor metabolic pathway for DA relative to O-methylation or oxidative deamination. The data also suggest that conjugation of DA occurs chiefly outside of the dopaminergic neurons in striatum.
结合作用（可能是与硫酸盐结合）是脑中3,4 - 二羟基苯乙胺（多巴胺，DA）可证实的代谢途径。开展了多项研究以确定在DA前体存在的情况下结合作用是否变得更具重要性。研究了3,4 - 二羟基苯丙氨酸（L - DOPA）和L - 酪氨酸对大鼠纹状体切片中游离和结合的DA、3,4 - 二羟基苯乙酸（DOPAC）和高香草酸流出的影响，实验在静止条件下以及由40 mM K⁺或5×10⁻⁵ M苯乙胺（PEA）诱发释放的过程中进行。结合的DA存在于纹状体切片的基础流出物中，并且在诱发释放期间其含量增加。在K⁺诱发释放期间，超滤液中存在的结合DA比PEA诱发释放期间更多。L - 酪氨酸（5×10⁻⁴ M或5×10⁻⁵ M）对结合DA的流出影响很小，但减少了PEA释放的游离DA的量，并减弱了在K⁺诱发递质释放期间发生的DOPAC的增加。L - DOPA（5×10⁻⁵ M）增加了结合DA的形成，但程度小于游离DA或DOPAC。因此，即使添加了前体，相对于O - 甲基化或氧化脱氨基作用而言，结合作用仍然是DA的一条次要代谢途径。数据还表明，DA的结合主要发生在纹状体中多巴胺能神经元之外。
