Tuinhof R, González A, Smeets W J, Scheenen W J, Roubos E W
Department of Cellular Animal Physiology, University of Nijmegen, The Netherlands.
Eur J Morphol. 1994 Aug;32(2-4):307-10.
Our research focusses on the role of brain and hypophysis in the control of background adaptation in the clawed toad, Xenopus laevis. This adaptation is regulated by alpha-melanophorestimulating hormone (alpha-MSH). Previously, it was shown that various neurotransmitters influence alpha-MSH release. Here we report about the origin of these factors. Using retrograde labelling techniques combined with immunocytochemistry, it was found that the inhibitory transmitters dopamine and neuropeptide Y coexist in neurons in the suprachiasmatic nucleus. These neurons project to the pars intermedia and synaptically contact the alpha-MSH-producing melanotrope cells. In the synapses also GABA is present. Tracing of the optic nerve indicated the presence of a direct retinosuprachiasmatic tract. Furthermore, locus coeruleus neurons project to the pars intermedia. They contain the inhibitory transmitter noradrenaline. The stimulatory factors corticotropin-releasing hormone and thyrotropin stimulating hormone originate from the magnocellular nucleus which send its processes to the neural lobe of the hypophysis.
我们的研究聚焦于大脑和垂体在爪蟾（非洲爪蟾）背景适应控制中的作用。这种适应由α-促黑素细胞激素（α-MSH）调节。此前研究表明，多种神经递质会影响α-MSH的释放。在此，我们报告这些因素的来源。运用逆行标记技术并结合免疫细胞化学方法，发现抑制性神经递质多巴胺和神经肽Y共存于视交叉上核的神经元中。这些神经元投射至垂体中间部，并与产生α-MSH的黑素细胞进行突触联系。在突触中也存在γ-氨基丁酸（GABA）。对视神经的追踪显示存在一条直接的视网膜-视交叉上核束。此外，蓝斑核神经元投射至垂体中间部。它们含有抑制性神经递质去甲肾上腺素。刺激性因子促肾上腺皮质激素释放激素和促甲状腺激素来自大细胞神经核，该神经核将其突起延伸至垂体神经叶。
