Erichsen J T, Ciocchetti A, Fontanesi G, Bagnoli P
Department of Neurobiology and Behavior, SUNY at Stony Brook 11794.
J Comp Neurol. 1994 Jul 22;345(4):537-61. doi: 10.1002/cne.903450406.
The avian hippocampal formation has previously been shown to contain many of the same neurotransmitters and related enzymes that are found in mammals. In order to determine whether the relatively delayed development of the mammalian hippocampus is typical of other vertebrates, we investigated the maturation of a variety of neuroactive substances in the hippocampal formation of the homing pigeon. The distribution of two transmitter-related enzymes, choline acetyltransferase (ChAT) and tyrosine hydroxylase (TH), the neurotransmitter GABA, and four neuropeptides (substance P, enkephalin, neuropeptide Y, and somatostatin) was studied by immunohistochemistry in the developing hippocampal complex. The pattern and/or the time course of changes in the distribution of immunoreactivity varied among the different neuroactive substances examined. Immunoreactivity to ChAT and TH was found exclusively in fibers and terminal-like processes, whereas GABA and peptide immunoreactivity was seen in cells and neuropil. Quantitative differences in the density, number, and size of stained cells were assessed by a computer-assisted image analyzer. For the majority of the substances, developmental patterns in the distribution of immunoreactivity differ between the hippocampus proper and the area parahippocampalis, the two major areas that together make up the avian hippocampal complex. The adult pattern of immunoreactivity was generally attained by 3 weeks after hatching. For many of the neuroactive substances found in cell bodies, there was a gradual decrease in the density of immunoreactive cells with a concomitant increase in the density of immunoreactive neuropil. The actual number of stained cells usually increased to a peak at 9 days posthatching and then declined until 3 weeks posthatching, when the adult value was reached. These results are discussed in relation to the advantages that the pigeon hippocampal complex may provide in the study of developmental processes. Parallels with the distribution of the same neuroactive substances in the mammalian hippocampus are used to suggest possible functional similarities between the avian and mammalian hippocampal regions.
先前的研究表明，鸟类海马结构中含有许多与哺乳动物相同的神经递质和相关酶。为了确定哺乳动物海马体相对延迟的发育是否是其他脊椎动物的典型特征，我们研究了归巢鸽海马结构中多种神经活性物质的成熟情况。通过免疫组织化学方法，研究了发育中的海马复合体中两种与递质相关的酶，即胆碱乙酰转移酶（ChAT）和酪氨酸羟化酶（TH）、神经递质γ-氨基丁酸（GABA）以及四种神经肽（P物质、脑啡肽、神经肽Y和生长抑素）的分布。在所检测的不同神经活性物质中，免疫反应性分布的模式和/或时间进程各不相同。ChAT和TH的免疫反应性仅在纤维和终末样突起中发现，而GABA和肽的免疫反应性则在细胞和神经毡中可见。通过计算机辅助图像分析仪评估染色细胞的密度、数量和大小的定量差异。对于大多数物质而言，免疫反应性分布的发育模式在构成鸟类海马复合体的两个主要区域——海马本部和海马旁区域之间存在差异。免疫反应性的成年模式通常在孵化后3周达到。对于许多在细胞体中发现的神经活性物质，免疫反应性细胞的密度逐渐降低，同时免疫反应性神经毡的密度相应增加。染色细胞的实际数量通常在孵化后9天增加到峰值，然后下降，直到孵化后3周达到成年值。本文结合鸽子海马复合体在发育过程研究中可能具有的优势对这些结果进行了讨论。通过与哺乳动物海马体中相同神经活性物质分布的对比，推测了鸟类和哺乳动物海马区域之间可能存在的功能相似性。
