REGULATION OF ENDOGENOUS DOPAMINE RELEASE IN AMPHIBIAN RETINA BY MELATONIN - THE ROLE OF GABA
REGULATION OF ENDOGENOUS DOPAMINE RELEASE IN AMPHIBIAN RETINA BY MELATONIN - THE ROLE OF GABA
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DOI：
10.1017/s0952523800003941
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发表时间：
1994-09-01
影响因子：
1.9
通讯作者：
IUVONE, PM
中科院分区：
文献类型：
--
作者：
BOATRIGHT, JH;RUBIM, NM;IUVONE, PM
在非洲爪蟾（Xenopus laevis）的视网膜中，内源性多巴胺的释放在光照下增加，在黑暗中减少。外源性褪黑激素及其类似物以浓度依赖性方式抑制蛙视网膜光诱发多巴胺释放。抑制光诱发多巴胺释放的效力的等级顺序为褪黑激素>> 5-甲氧基色胺大于或等于N-乙酰血清素> 5-甲氧基羟色胺>> 5-羟色胺。褪黑激素没有抑制多巴胺释放低于黑暗中看到的水平。褪黑激素受体拮抗剂luzindole可抑制褪黑激素的作用。Luzindole在黑暗中增强多巴胺的释放，但在光照下几乎没有影响。这些数据表明内源性褪黑激素在黑暗诱导的视网膜多巴胺抑制中的作用。印防己毒素和荷包牡丹碱，GABA-A受体拮抗剂，阻断褪黑激素诱导的多巴胺释放抑制。在褪黑激素的存在下，荷包牡丹碱在刺激多巴胺释放方面的效力显著降低。这些结果表明，褪黑激素增强光诱发的多巴胺释放的GABA能抑制。这种机制可能是脊椎动物视网膜中多巴胺释放的明/暗差异的基础。
In the retina of the African clawed frog (Xenopus laevis), endogenous dopamine release increases in light and decreases in darkness. Exogenous melatonin and several chemical analogs of melatonin suppressed light-evoked dopamine release from frog retina in a concentration-dependent manner. The rank order of potency for inhibition of light-evoked dopamine release was melatonin >> 5-methoxytryptamine greater than or equal to N-acetylserotonin > 5-methoxytryptophol >>> serotonin. Melatonin did not suppress dopamine release below levels seen in darkness. The putative melatonin receptor antagonist luzindole inhibited the effect of melatonin. Luzindole enhanced dopamine release in darkness but had little effect in light. These data suggest a role for endogenous melatonin in dark-induced suppression of retinal dopamine.Picrotoxin and bicuculline, GABA-A receptor antagonists, blocked melatonin-induced suppression of dopamine release. In the presence of melatonin, bicuculline was significantly less potent in stimulating dopamine release. These results suggest that melatonin enhances GABAergic inhibition of light-evoked dopamine release. This mechanism may underlie the light/dark difference in dopamine release in vertebrate retina.