Multiple inputs of GABA-immunoreactive neurons in the cuneate nucleus of the rat.
Using anterograde transport of WGA-HRP and the experimental degeneration method for identification of corticocuneate (CCT) and primary afferent (PAT) terminals in conjunction with gamma-amino butyric acid (GABA) and glutamate immunocytochemistry, this study has demonstrated that the GABA-immunoreactive (GABA-IR) neurons in the rat cuneate nucleus were post-synaptic to PATs (some of them being glutamate-IR), GABA-IR and GABA-negative terminals. The HRP-labelled CCTs did not make any synaptic contacts with GABA-IR neurons but with some GABA-negative dendrites. PATs labelled by HRP or showing degenerating features made direct synaptic contacts with the dendrites of GABA-IR neurons. Beside the above GABA-IR boutons also showed axosomatic and axodendritic synapses with the GABA-IR neurons. In 'triple labeling' method for GABA, PAT and glutamate, it was found that the PATs which were usually glutamate-positive were presynaptic to the dendrites of GABA-IR neurons. Furthermore, some glutamate-IR terminals which were of non-PAT's origin also synapsed with the dendrites and somata of GABA-IR neurons. It is concluded from this study that the major inputs of GABA-IR neurons were from glutamate immunopositive PATs and glutamate terminals of non-PATs origin; other GABA-IR terminals either intrinsic or extrinsic also contributed to the afferent sources of GABA-IR neurons. The CCTs contributed very little, if any, to this input. It is suggested that the PATs and glutamate-IR terminals on GABA-IR neurons may be involved in lateral inhibition for increase of spatial precision. The synaptic contacts between GABA-IR boutons and dendrites or somata of GABA-IR neurons may provide a possible means for disinhibition.
Lue
J H
JH
Department of Anatomy, College of Medicine, National Taiwan University, ROC.
Jiang-Shieh
Y F
YF
Shieh
J Y
JY
Ling
E A
EA
Wen
C Y
CY
D000818:Animals; D001479:Basal Ganglia / Q000166:cytology / Q000502:physiology*; D002540:Cerebral Cortex / Q000166:cytology / Q000502:physiology*; D018698:Glutamic Acid / Q000502:physiology; D007091:Image Processing, Computer-Assisted; D007124:Immunoenzyme Techniques; D007150:Immunohistochemistry; D008297:Male; D009411:Nerve Endings / Q000502:physiology; D009434:Neural Pathways / Q000166:cytology / Q000502:physiology; D009474:Neurons / Q000502:physiology*; D009475:Neurons, Afferent / Q000502:physiology; D017729:Presynaptic Terminals / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D018998:Wheat Germ Agglutinin-Horseradish Peroxidase Conjugate; D005680:gamma-Aminobutyric Acid / Q000502:physiology*
D018998:Wheat Germ Agglutinin-Horseradish Peroxidase Conjugate; D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid