| Budget Amount *help |
¥3,700,000 (Direct Cost: ¥3,700,000)
Fiscal Year 2001: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 2000: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1999: ¥2,700,000 (Direct Cost: ¥2,700,000)
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| Research Abstract |
The present study has revealed the synaptic organization constructed by chemically-defined interneurons in the glomerular layer of the rat olfactory bulb.
Previously, we have clarified the heterogenelty of periglomerular (PG) Interneuros in their chemical and structural features. Then the PG neurons could be classified into three distinct groups GABA- or Tyrosine Hydroxylase-immunoreactive (TH-IR), Calbindin (CB)-IR, and Calretinin (CR)-IR neuronal groups. In the present study, the synapses formed by these neurons have been identified quantitatively by correlative confocal and serial electron microscopy.
GABAergic TH-neurons exhibited the unique synaptic formation. They received asymmetrical synapses mainly from olfactory nerve (ON) terminals. In addition, they received asymmetrical synapses from the mitral/tufted (M/T) cells, although in small number, and in turn, formed symmetrical synapses to M/T cells. Thus TH-neurons formed two types of serial synapses ; (1) asymmetrical synapse fro
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m ON terminals and symmetrical one serially to M/T cells and (2) asymmetrical synapse from M/T cells and symmetrical one serially to different M/T cells. So far no reciprocal synapses with M/T cells have been observed (Toida et al 2000). These synaptic types were in contrast to those of GABA-immunonegative CB-neurons (Toida et al 1998). CR-neurons, which are also GABA immunonegative, exhibited similar features of synaptic types of CB-neurons.
Thus our study clarified the heterogeneity in synaptic organization constructed by chemically-defined interneurons. These findings further suggested that these chemically-defined neurons exhibited different functional effects on olfactory bulb synaptic circuitry (Toida et al 2002).
In addition, in this study, we have obtained new findings about neurosteroid metabolism in the rat olfactory bulb. We have revealed the possible presence of some steroid-synthesizing enzymes by means of immunocytochemistry and biochemistry. We have been analyzing their functional roles on neuronal and synaptic organization in olfactory information processing. Less
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