Analyses on the juxtaglomerular neurons of the olfactory bulb : 2 types of periglomerular cells

在嗅球中，作为嗅觉的第一中枢，小球被认为是一个功能单位，因此在嗅觉信息处理中起着重要作用。在本研究中，我们考察了以下三点。(1)肾小球周围细胞，1型和2型，有轴突吗？我们使用1型和2型小球周围细胞以及轴突起始节段的化学标记物的抗体进行多重荧光免疫染色，如AnkyrinG、Nav和βIV-Spectrin。激光共聚焦扫描显示，大型型酪氨酸羟化酶(TH)阳性的GABA能球旁神经元、一氧化氮合酶(NOS)阳性的外丛细胞和短轴突细胞表达NOS、钙结合蛋白和小白蛋白(PV)。然而，大多数对嗅球球旁神经元的分析：两种类型的球周细胞球周细胞没有显示化学鉴定的轴突起始节段，表明这些球周细胞是…。更具再生障碍性。(2)GABA能球旁TH阳性神经元是成年期产生的主要神经元之一。另一方面，有两种类型的TH阳性神经元，大的和小的，正如我们先前所揭示的那样，大的TH阳性神经元显示出长时间的轴突延伸到远处的肾小球，形成抑制性联系系统。在本研究中，我们确定了这两种类型的TH阳性神经元的出生时间，以及成人产生的TH阳性神经元是否包括这两种类型。在不同发育阶段注射BrdU；产前(E13、E17)、新生儿(P3)和少年或成人(P4w或8w)。这一分析表明，大的和小的TH阳性神经元都在产前和新生儿时期产生。但只有少量的TH阳性神经元是成人产生的神经元。(3)在外丛状层无轴突状PV阳性GABA能神经元的树突节段上发现了特殊的轴突起始节段性或节点状的Ranvier样位点。这些热点表达轴突起始段的化学标记，并进一步显示出轴突起始段、膜底膜的超微结构特征。因此，这些热点被认为是尖峰产生的地点。较少

In the olfactory bulb, the first center of the olfaction, the glomerulus is considered as a functional unit and thus to be important in the olfactory information processing. In the present study we examined following three points. (1) Do the periglomerular cells, type 1 and type 2, have axons? We applied multiple fluorescent immunostaining using antibodies of chemical markers for type 1 and 2 periglomerular cells as well as for axon initial segments, such as AnkyrinG, Nav, and βIV-spectrin. The confocal laser scanning observations revealed that large type of tyrosine hydroxylase (TH) positive GABAergic juxtaglomerular neurons, nitric oxide synthase (NOS) positive external tufted cells and short-axon cells expressing NOS, calbindin and parvalbumin (PV). However, most of Analyses on the juxtaglomerular neurons of the olfactory bulb : 2 types of periglomerular cells periglomerular cells did not show the chemically identified axon initial segments, indicating those periglomerular cells are … More anaxonic. (2) As well known TH positive GABAergic juxtaglomerular neurons are one of major groups of neurons generated even in adult period. On the other hand, there two types of TH positive neurons, large and small ones, and as we previously revealed the large type of TH positive neurons show long extending axonal processes to distant glomeruli making the inhibitory association system. In the present study we determined when both types of TH positive neurons are born and whether adult-generated TH positive neurons include both types. BrdU were injected at various developmental stages; prenatal period (E13, E17), neonate (P3) and juvenile or adult (P4w or 8w). This analysis revealed that both large and small TH positive neurons generated during prenatal and neonate periods. But only small type of TH positive neurons are adult-generated neurons. (3) We found particular axon initial segment-like or node of Ranvier-like sites "hot spots" on the dendritic segments of anaxonic PV positive GABAergic neurons in the external plexiform layer. These hot spots expressed chemical markers for axon initial segments and furthermore showed the ultrastructural feature characteristic to axon initial segment, membrane undercoating. Thus these hot spots are supposed to be the spike generating sites. Less