Kosaka Katsuko, Kosaka Toshio
School of Health Sciences, Faculty of Medicine, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.
Anat Sci Int. 2005 Jun;80(2):80-90. doi: 10.1111/j.1447-073x.2005.00092.x.
According to the combinatorial receptor and glomerular codes for odors, the fine tuning of the output level from each glomerulus is assumed to be important for information processing in the olfactory system, which may be regulated by numerous elements, such as olfactory nerves (ONs), periglomerular (PG) cells, centrifugal nerves and even various interneurons, such as granule cells, making synapses outside the glomeruli. Recently, structural and physiological analyses at the cellular level started to reveal that the neuronal organization of the olfactory bulb may be more complex than previously thought. In the present paper, we describe the following six points of the structural organization of the glomerulus, revealed by confocal laser scanning microscopy and electron microscopy analyses of rats, mice and other mammals: (i) the chemical heterogeneity of PG cells; (ii) compartmental organization of the glomerulus, with each glomerulus consisting of two compartments, the ON zone and the non-ON zone; (iii) the heterogeneity of PG cells in terms of their structural and synaptic features, whereby type 1 PG cells send their intraglomerular dendrites into both the ON and non-ON zones and type 2 PG cells send their intraglomerular dendrites only into the non-ON zone, thus receiving either few synapses from the ON terminals, if present, or none at all; (iv) the spatial relationship of mitral/tufted cell dendritic processes with ON terminals and PG cell dendrites; (v) complex neuronal interactions via chemical synapses and gap junctions in the glomerulus; and (vi) comparative aspects of the organization of the main olfactory bulb.
根据气味的组合受体和肾小球编码，假定每个肾小球输出水平的精细调节对于嗅觉系统中的信息处理很重要，这可能受多种因素调节，如嗅神经（ONs）、球周（PG）细胞、离心神经，甚至各种中间神经元，如颗粒细胞，它们在肾小球外形成突触。最近，细胞水平的结构和生理分析开始揭示，嗅球的神经元组织可能比以前认为的更复杂。在本文中，我们描述了通过对大鼠、小鼠和其他哺乳动物进行共聚焦激光扫描显微镜和电子显微镜分析所揭示的肾小球结构组织的以下六点：（i）PG细胞的化学异质性；（ii）肾小球的分区组织，每个肾小球由两个区室组成，即ON区和非ON区；（iii）PG细胞在结构和突触特征方面的异质性，其中1型PG细胞将其球内树突发送到ON区和非ON区，2型PG细胞仅将其球内树突发送到非ON区，因此如果有来自ON终末的突触，则接收很少，或者根本不接收；（iv）二尖瓣/簇状细胞树突过程与ON终末和PG细胞树突的空间关系；（v）肾小球中通过化学突触和缝隙连接的复杂神经元相互作用；以及（vi）主嗅球组织的比较方面。
