Immunocytochemical analysis of the development of chemically defined neurons in the olfactory bulb

在大鼠嗅球中，肾小球层（GL）和外网状层（EPL）的中间神经元大多数在出生后第一周产生。在本研究中，我们研究了1）多巴胺能神经元和2）含有钙结合蛋白小清蛋白（PV）的神经元的发育。1）多巴胺能神经元的发育可塑性。新生儿X线照射对嗅球神经元尤其是多巴胺能神经元的影响用体视学和免疫细胞化学方法观察了成年动物的TH阳性神经元。照射后，GABA（-）TH（+）细胞占TH（+）细胞的比例增加到对照组的2倍左右，γ-氨基丁酸（-）TH（+）细胞总数分别为对照组的95%（800 rad）和40%（1200 rad）。这些观察结果表明，大多数GABA（-）TH（+）神经元在出生后第一周内受X射线照射的影响较小，因此，它们可能是在产前时期产生的。在生后2周内，GL未见GABA（-）TH（+）阳性神经元（Kokaran等人，1987 a），成年人嗅球中的大多数GABA（-）TH（+）神经元在出生后的某个发育时期发生了表型变化。PV神经元的发育本实验首先研究了PV神经元在成年大鼠嗅球内的层分布和形态学特征，研究其生后发育变化。EPL内PV（+）神经元明显不均一，可分为几类。PV（+）神经元最早出现于P10，主要位于EPL的内缘，P14 ~ P21时PV（+）神经元数量明显增多。本研究进一步揭示了外胚叶内、外亚层在生后发育中的差异。

In the rat olfactory bulb, the majority of interneurons in the glomerular layr (GL) and external plexiform layr (EPL) are supposed to be generated during first postnatal week. In the present study we investigated developments of 1)dopaminergic neurons and 2)neurons containing a calcium-binding protein parvalbumin (PV).1)Developmental plasticity of dopaminergic neurons. The effects of neonatal X-rayirradiation , which were used to impair the development of interneurons, on olfactory bulb neurons, especially dopaminergic neurons (TH positive neurons) were examined stereologically and immunocytochemically in adult animals, In irradiated bulbs the proportion of GABA(-)TH(+) cells in TH(+) cells increased to about twice of control, and the estimated total numbers of GABA(-)TH(+) cells in irradiated rats were 95%(800rad) and 40% (1200rad) of control. These observations suggest that the majority of GABA(-)TH(+) neurons were less affected by X-ray irradiation during the first postnatal week and thus that they might be generated in the prenatal period. Since during the first 2 postnatal weeks, neurons showing GABA(-)TH(+) were not seen in GL (Kosaka et al.1987a), the majority of GABA(-)TH(+) neurons in adult olfactory bulb were assumed to change their phenotype at some postnatal developmental period.2)Development of PV neurons The laminar distribution and morphological features of PV neurons were firstly studied in the adult rat olfactory bulb and then their developmental changes were studies postnatally. PV(+) neurons in the EPL were apparently heterogeneous and appeared to be classifiable into several groups. PV(+) neurons first appeared at P10 mainly in the inner border of EPL and they were increased remarkably in number during P14 to P21. The present study further showed the difference between inner sublayr and outer sublayr of the EPL in the postnatal development.