|Budget Amount *help
¥3,800,000 (Direct Cost : ¥3,800,000)
Fiscal Year 2004 : ¥700,000 (Direct Cost : ¥700,000)
Fiscal Year 2003 : ¥3,100,000 (Direct Cost : ¥3,100,000)
The present study aimed to reveal dendritic synapses of projection neurons in the rat main olfactory bulb by means of serial-sectioning electron microscopy.
The projection neurons of the olfactory bulb, mitral and tufted (M/T) cells, extended their dendrites to glomerul and the external plexiform layer (EPL). In the glomerular layer, they received asymmetrical synapses from olfactory nerves (ON) and formed synaptic contacts with the inerneurons, which were heterogeneous in their chemical nature. Tyrosine hydroxylase (TH)-immunoreactive neurons received asymmetrical synapses from ON and dendrites of the projection neurons, and further made symmetrical synapses to the different projection neurons, thus forming serial synapses. The TH-neurons extended their dendrites rather extensively in the glomerulus to form serial synapses through different intraglomerular subcompartments. In contrast, calbindin (CB)- and calretinin (CR)-immunoreactive neurons formed reciprocal synapses with the same p
rojection neurons. They extended their dendrites locally in the single subcompartment in the glomerulus.
In the EPL, granule cells frequently formed reciprocal synapses with M/T cells. PV-neurons also made synapses with M/T cells, but they made predominantly serial synapse with pleural M/T cells rather than reciprocal synapses with the single M/T cells. Synapses of granule cells with W/T cells were observed throughout the EPL, but PV-neurons tended to made at more proximal part of the dendrites. These synapses in the EPL were also found in the mitral cell layer. Interestingly, PV-neurons extended their dendrites between mitral cells with serial synapses with them.
As reciprocal and serial synapses could be suggested to lateral inhibition and recurrent modulation functionally, these heterogeneous synapses with the projection neurons formed by chemical subpopulation were implicated to elaborate regulation in the olfactory bulb synaptic circuitry.
In the present project term, we examined neurosteroid, circadian clock gene, opioid and autonomic nervous system as possible candidates for regulating olfactory circuitry and carried out preliminary experiments. Less