Jia W W, Liu Y, Lepore F, Ptito M, Cynader M
Department of Ophthalmology, University of British Columbia, Vancouver, Canada.
Neuroscience. 1994 Nov;63(1):179-90. doi: 10.1016/0306-4522(94)90015-9.
Alpha-1 and alpha-2 adrenergic receptors were localized in developing cat visual cortex by using [3H]prazosin and [3H]rauwolscine, respectively as selective ligands. The effects of neuronal input on the development of the two receptor subtypes were also studied in animals with lesions at various sites within the central visual pathways. Binding densities for both ligands increased during the first few postnatal weeks and declined thereafter. For both receptor subtypes, the highest concentration of binding sites was found in the subplate zone of the cortex in neonatal animals. Both ligands showed their highest concentrations in cortical layer IV beginning at postnatal day 30 and in the superficial cortical layers in adulthood. However, the developmental redistribution of alpha-1 receptors began at earlier ages than that of the alpha-2 sites. The alpha-1 sites were still concentrated in the subplate zone up to 60 days postnatal, while the alpha-2 sites in this region disappeared much earlier. Receptor binding densities were also examined in animals with quinolinic acid lesions within cortex, lesions of the lateral geniculate nucleus and lesions of the optic tract. The results indicate that both alpha-adrenoceptor subtypes were mainly located on cortical cells, and that the absence of neuronal activity during development resulted in a reduction of the binding density for both subtypes in the visual cortex. An additional major reduction in alpha-2 but not alpha-1 binding sites was observed following the lateral geniculate nucleus lesion, suggesting that the development of alpha-2 receptors is also dependent on input from the lateral geniculate nucleus. Removal of the lateral geniculate nucleus early in life resulted in a significant increase in alpha-1 receptors in the subplate region, indicating that receptor densities in this zone may be negatively regulated by the lateral geniculate nucleus afferents. These results show that adrenergic receptors reorganize during postnatal cortical development with a strong temporary concentration in the subplate zone. The reorganization process is heavily influenced by cortical inputs.
分别使用[3H]哌唑嗪和[3H]萝芙木碱作为选择性配体，对发育中的猫视觉皮层中的α1和α2肾上腺素能受体进行了定位。还在中枢视觉通路内不同部位有损伤的动物中研究了神经元输入对这两种受体亚型发育的影响。两种配体的结合密度在出生后的头几周内增加，随后下降。对于这两种受体亚型，在新生动物的皮层板下区发现结合位点的浓度最高。两种配体在出生后第30天开始在皮层第IV层显示出最高浓度，在成年期则在皮层浅表层显示出最高浓度。然而，α1受体的发育重新分布比α2位点开始得更早。α1位点在出生后60天内仍集中在皮层板下区，而该区域的α2位点消失得更早。还对皮层内有喹啉酸损伤、外侧膝状体损伤和视束损伤的动物的受体结合密度进行了检查。结果表明，两种α肾上腺素能受体亚型主要位于皮层细胞上，并且发育过程中神经元活动的缺失导致视觉皮层中两种亚型的结合密度降低。在外侧膝状体损伤后，观察到α2而非α1结合位点有额外的大幅减少，这表明α2受体的发育也依赖于来自外侧膝状体的输入。生命早期去除外侧膝状体导致皮层板下区域的α1受体显著增加，表明该区域的受体密度可能受到外侧膝状体传入纤维的负调控。这些结果表明，肾上腺素能受体在出生后皮层发育过程中会重新组织，在皮层板下区有强烈的暂时集中。重组过程受到皮层输入的严重影响。
