| Budget Amount *help |
¥1,900,000 (Direct Cost: ¥1,900,000)
Fiscal Year 1993: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1992: ¥1,300,000 (Direct Cost: ¥1,300,000)
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| Research Abstract |
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.
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