Kramer B M, Welting J, Berghs C A, Jenks B G, Roubos E W
Department of Cellular Animal Physiology, Nijmegen Institute for Neurosciences, University of Nijmegen, 6525 ED Nijmegen, The Netherlands.
J Comp Neurol. 2001 Apr 9;432(3):346-55. doi: 10.1002/cne.1107.
The process of background adaptation in the toad Xenopus laevis is controlled by neurons in the suprachiasmatic nucleus (SC) that inhibit the release of alpha-melanophore-stimulating hormone from the neuroendocrine melanotrope cells in the pituitary gland. We have identified the structural and functional organization of different neuropeptide Y (NPY)-containing cell groups in the Xenopus SC in relation to background adaptation. A ventrolateral, a dorsomedial, and a caudal group were distinguished, differing in location as well as in number, size, and shape of their cells. They also show different degrees of NPY immunoreactivity in response to different background adaptation conditions. In situ hybridization using a Xenopus mRNA probe for the exocytosis protein DOC2 revealed that melanotrope cells of black-adapted animals have a much higher expression of DOC2-mRNA than white-adapted ones. This establishes that the degree of DOC2-mRNA expression is a good parameter to measure cellular secretory activity in Xenopus. We show that in the ventrolateral SC group, more NPY-positive neurons express DOC2-mRNA in white- than in black-adapted animals. In contrast, NPY-positive neurons in the dorsomedial group have a high secretory activity under the black-adaptation condition. We propose that in black-adapted animals, NPY-positive neurons in the ventrolateral group, known to inhibit the melanotrope cells in white-adapted animals synaptically, are inhibited by NPY-containing interneurons in the dorsmedial group. NPY-positive neurons in the caudal group have similar secretory dynamics as the dorsomedial NPY neurons, indicating that they also play a role in background adaptation, distinct from that exerted by the ventrolateral and dorsomedial group.
非洲爪蟾（Xenopus laevis）的背景适应过程由视交叉上核（SC）中的神经元控制，这些神经元抑制垂体神经内分泌黑素细胞释放α - 促黑素细胞激素。我们已经确定了非洲爪蟾视交叉上核中不同的含神经肽Y（NPY）细胞群的结构和功能组织与背景适应的关系。区分出了腹外侧、背内侧和尾侧细胞群，它们在位置以及细胞数量、大小和形状上存在差异。它们在不同的背景适应条件下也表现出不同程度的NPY免疫反应性。使用非洲爪蟾胞吐蛋白DOC2的mRNA探针进行原位杂交显示，黑色适应动物的黑素细胞中DOC2 - mRNA的表达比白色适应动物高得多。这表明DOC2 - mRNA的表达程度是衡量非洲爪蟾细胞分泌活性的一个良好参数。我们发现，在腹外侧视交叉上核细胞群中，白色适应动物中表达DOC2 - mRNA的NPY阳性神经元比黑色适应动物更多。相反，背内侧细胞群中的NPY阳性神经元在黑色适应条件下具有较高的分泌活性。我们提出，在黑色适应动物中，腹外侧细胞群中已知在白色适应动物中通过突触抑制黑素细胞的NPY阳性神经元，受到背内侧含NPY中间神经元的抑制。尾侧细胞群中的NPY阳性神经元具有与背内侧NPY神经元相似的分泌动态，表明它们在背景适应中也发挥作用，与腹外侧和背内侧细胞群的作用不同。
