| Budget Amount *help |
¥2,700,000 (Direct Cost: ¥2,700,000)
Fiscal Year 2001: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 2000: ¥2,000,000 (Direct Cost: ¥2,000,000)
|
|---|
| Research Abstract |
γ-aminobutyric acid (GABA) is a main inhibitory neurotransmitter in the central nervous system and thought to be critically involved in regulating excitatory neurotransmission. For the inhibitory neurotransmission, GABAA receptors, a pentameric hetero-oligomer ligand-gated chloride channel consisting mainly of α,β and γ subunits, must be clustered at the postsynaptic membranes. In the present study, how GABAergic synaptic activity and expression of molecules responsible for the receptor-mediated transmission are regulated and correlated with each other during development,was addressed in the nucleus of the tractus solitarius (NTS). GABAergic inhibitory postsynaptic currents (IPSCs) and expression of GABAA receptqrγ1-subunit, which is essential for the receptor clustering at the postsynaptic membranes, were consistently evident in small sized neurons of the caudal NTS during the early postnatal period (P1-6). After the first postnatal week, both IPSCs and expression of GABAA receptorγ1-subunit virtually disappeared in these neurons. Low level expression of GABAA receptorγ2-subunit and gephyrin were consistently observed in the NTS. Electron microscopy revealed that numbers of GABAergic axosomatic synapses were decreased and virtually disappeared during the development. These results show that GABAergic synaptic activity and γ1 subunit expression were closely associated with each other and that they are developmentally regulated in specific type of NTS neurons for an establishment of mei local neuronal networks of adult type. This phenomenon may underlie an establishment of cardiovascular and respiratory reflex circuits in the medulla.
|
