Leranth C, Nitsch R
Department of Obstetrics and Gynecology, Yale University, School of Medicine, New Haven, Connecticut 06520.
J Neurosci. 1994 Jul;14(7):4079-94. doi: 10.1523/JNEUROSCI.14-07-04079.1994.
This study in the African green monkey (Cercopithecus aethiops) was designed to characterize the neurochemical features of hippocampal nonpyramidal neurons that are specific synaptic targets of substance P-containing projective neurons located in the supramammillary nucleus. Our previous studies provided evidence for an excitatory nature to this hypothalamo-hippocampal pathway and described the mode of termination of these afferents on hippocampal principal neurons. The present correlated light and electron microscopic immunocytochemical analysis, using the nickel-diaminobenzidine/diaminobenzidine double-labeling technique, revealed that this hippocampal afferent system establishes multiple, exclusively asymmetric synapses with three specific subpopulations of nonpyramidal cells: (1) a small portion of parvalbumin-containing basket cells located periodically in or adjacent to the granule cell layer of the dentate gyrus, which therefore inhibit only a subpopulation of granule cells; (2) some of the calbindin-immunoreactive local circuit neurons located in the hilar area; and (3) calbindin-positive cells occurring exclusively in the stratum molecular of the middle portion of the CA3 subfield. Postembedding studies revealed that the aforementioned calbindin-containing cells are GABAergic inhibitory neurons. Our studies indicate that hypothalamic afferents can effectively filter the information flow at different levels of the excitatory signal loop in the monkey hippocampal formation. Dentate granule cells, which are only stimulated by hypothalamic afferents, will transfer excitatory signals differently than those that are controlled by a feedforward inhibitory mechanism initiated by these fibers. In the CA3 subfield, the signal flow can again be depressed by those pyramidal neurons that are inhibited by calbindin-containing cells receiving an excitatory hypothalamic input.
本研究以非洲绿猴（猕猴）为对象，旨在表征海马非锥体神经元的神经化学特征，这些神经元是位于乳头体上核的含P物质投射神经元的特定突触靶点。我们之前的研究证明了这条下丘脑 - 海马通路具有兴奋性，并描述了这些传入纤维在海马主神经元上的终止方式。目前，采用镍 - 二氨基联苯胺/二氨基联苯胺双重标记技术进行的相关光镜和电镜免疫细胞化学分析显示，这个海马传入系统与三种特定的非锥体细胞亚群建立了多个、完全不对称的突触：（1）一小部分含小白蛋白的篮状细胞，它们周期性地位于齿状回颗粒细胞层内或其附近，因此仅抑制一部分颗粒细胞；（2）一些位于海马门区的钙结合蛋白免疫反应性局部回路神经元；（3）仅出现在CA3亚区中部分子层的钙结合蛋白阳性细胞。包埋后研究表明，上述含钙结合蛋白的细胞是γ-氨基丁酸能抑制性神经元。我们的研究表明，下丘脑传入纤维可以有效地在猴海马结构兴奋性信号回路的不同水平上过滤信息流。仅受下丘脑传入纤维刺激的齿状回颗粒细胞传递兴奋性信号的方式，将不同于那些受这些纤维启动的前馈抑制机制控制的颗粒细胞。在CA3亚区，信号流可以再次被那些接受兴奋性下丘脑输入的含钙结合蛋白细胞所抑制的锥体神经元所抑制。
