GABA/glycine signaling during degeneration and regeneration of mouse hypoglossal nerves.
In the adult central nervous system (CNS), GABA and glycine (Gly) are predominant inhibitory neurotransmitters, negatively regulating glutamatergic transmission. In the immature CNS, on the other hand, they act as trophic factors, mediating morphogenesis. In the present study, to investigate their involvement in axonal regeneration, we morphologically examined changes in their signaling in mouse hypoglossal nuclei during degeneration and regeneration of hypoglossal nerves. We found that (1) expression and localization of presynaptic elements were not changed, (2) localization of gephyrin, which anchors GABA and Gly receptors, was spread on the surface of motor neuron cell bodies and dendrites, (3) KCC2-expression markedly decreased, (4) choline acetyltransferase, which mediates acetylcholine-synthesis, immediately disappeared from the motor neurons, and (5) the synaptic cleft of both excitatory and inhibitory synapses became irregularly wider, in the hypoglossal nuclei of the sutured side after the operation. These changes gradually normalized during regeneration. These results suggested that synthesis of acetylcholine may be stopped in the motor neuron after axotomy. GABA/Gly may be normally released from presynaptic terminals, be spilled over the original synaptic cleft, be diffused into the neighboring space, bind to extrasynaptically localized receptors, and mediate depolarization of the membrane potential of motor neurons during degeneration and regeneration. Furthermore, it was suggested that GABA/Gly signaling in postsynaptic motor neurons went back to being immature after axotomy, and may play an important role in axonal regeneration.
Department of Molecular Anatomy, School of Medicine, University of the Ryukyus, Uehara 207, Nishihara, Okinawa, 9030215, Japan.
Masaharu
M
Tatetsu
Jeongtae
J
Kim
Shinichiro
S
Kina
Hajime
H
Sunakawa
Chitoshi
C
Takayama
D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism; D002772:Cholera Toxin / Q000378:metabolism; D002795:Choline O-Acetyltransferase / Q000378:metabolism; D005786:Gene Expression Regulation / Q000502:physiology; D005968:Glutamate Decarboxylase / Q000378:metabolism; D005998:Glycine / Q000378:metabolism*; D020437:Hypoglossal Nerve Diseases / Q000150:complications; D008526:Medulla Oblongata / Q000378:metabolism / Q000473:pathology / Q000648:ultrastructure; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D046529:Microscopy, Electron, Transmission; D009410:Nerve Degeneration / Q000209:etiology / Q000378:metabolism*; D009416:Nerve Regeneration / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology*; D027981:Symporters / Q000378:metabolism; D016708:Synaptophysin / Q000378:metabolism; D013997:Time Factors; D050495:Vesicular Inhibitory Amino Acid Transport Proteins / Q000378:metabolism; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*; D000096922:K Cl- Cotransporters
D002352:Carrier Proteins; D002772:Cholera Toxin; D002795:Choline O-Acetyltransferase; D005968:Glutamate Decarboxylase; D005998:Glycine; D008565:Membrane Proteins; D027981:Symporters; D016708:Synaptophysin; D050495:Vesicular Inhibitory Amino Acid Transport Proteins; D005680:gamma-Aminobutyric Acid; D000096922:K Cl- Cotransporters; C492244:Viaat protein, mouse; C073441:gephyrin