Krause D N, Siuciak J A, Dubocovich M L
Department of Pharmacology, College of Medicine, University of California at Irvine 92717.
Brain Res. 1994 Aug 15;654(1):63-74. doi: 10.1016/0006-8993(94)91571-7.
In chick brain, specific 2-[125I]-iodomelatonin-binding was localized primarily in the visual system, i.e., retinorecipient and relay nuclei and fiber tracts of the tectofugal, thalamofugal, circadian and accessory visual pathways. Unilateral transection of the optic nerve (ONX) significantly reduced the binding of 2-[125I]-iodomelatonin (75 pM) in many, but not all, primary retinal targets and visual pathways at 7 and 14 days, but not 1 day, postlesion. As measured using quantitative autoradiography, 2-[125I]-iodomelatonin binding was decreased by 90% in both the central portion of the lesioned optic tract and one of its targets, the nucleus of the basal optic root (nBOR). Other retinorecipient areas exhibiting substantial decreases (60%) in 2-[125I]-iodomelatonin-binding included the optic tectum, lateroventral and dorsolateral geniculate nuclei and tectal gray area contralateral to the lesion. These findings are consistent with the hypothesis that melatonin receptors are located presynaptically on incoming optic nerve terminals in many retinorecipient areas. This localization may account for most of the binding sites in nBOR. In other primary visual areas, however, melatonin receptors also appear to be located on postsynaptic cells and/or non-retinal afferents. ONX had no significant effect on 2-[125I] -iodomelatonin binding in two retinorecipient areas, the visual suprachiasmatic nucleus and the dorsolateral anterior thalamus, which are part of the circadian/oculomotor and thalamofugal pathways, respectively. An unexpected consequence of ONX was that 2-[125I]- iodomelatonin binding was decreased in certain secondary (nucleus rotundus, isthmi nuclei) and tertiary level (ectostriatum) nuclei along the prominent tectofugal visual pathway. Binding in the tectorecipient nucleus triangularis was not significantly altered, however. Analysis of secondary level relay nuclei in the oculomotor pathway revealed that binding after ONX was decreased in the ipsilateral Edinger-Westphal nucleus but not in the oculomotor nuclei. Selective transsynaptic changes in 2-[125I]-iodomelatonin binding after lesion of the visual input most likely reflect activity-dependent regulation and functional plasticity of central melatonin receptors.
在鸡脑中，特异性的2-[125I] - 碘褪黑素结合主要定位于视觉系统，即顶盖传出、丘脑传出、昼夜节律和辅助视觉通路的视网膜接收和中继核以及纤维束。视神经单侧横断（ONX）在损伤后7天和14天，而非1天，显著降低了许多（但并非全部）初级视网膜靶区和视觉通路中2-[125I] - 碘褪黑素（75 pM）的结合。使用定量放射自显影法测量发现，损伤的视束中央部分及其靶区之一基底视根核（nBOR）中，2-[125I] - 碘褪黑素结合减少了90%。其他显示2-[125I] - 碘褪黑素结合显著减少（60%）的视网膜接收区包括视顶盖、外侧腹侧和背外侧膝状核以及损伤对侧的顶盖灰质区。这些发现与褪黑素受体位于许多视网膜接收区传入视神经终末突触前的假说一致。这种定位可能解释了nBOR中的大部分结合位点。然而，在其他初级视觉区，褪黑素受体似乎也位于突触后细胞和/或非视网膜传入纤维上。ONX对两个视网膜接收区，即视交叉上核和背外侧前丘脑的2-[125I] - 碘褪黑素结合没有显著影响，它们分别是昼夜节律/动眼神经通路和丘脑传出通路的一部分。ONX一个意外的结果是，沿着突出的顶盖传出视觉通路，某些二级（圆核、峡核）和三级水平（外纹状体）核中的2-[125I] - 碘褪黑素结合减少。然而，顶盖接收核三角核中的结合没有显著改变。对动眼神经通路中二级中继核的分析表明，ONX后同侧动眼神经副核中的结合减少，但动眼神经核中没有减少。视觉输入损伤后2-[125I] - 碘褪黑素结合的选择性跨突触变化很可能反映了中枢褪黑素受体的活动依赖性调节和功能可塑性。
