Relationship between two types of vesicular glutamate transporters and neurokinin-1 receptor-immunoreactive neurons in the pre-Bötzinger complex of rats: light and electron microscopic studies.
Our previous study demonstrated GABAergic and glycinergic synapses onto neurokinin-1 receptor (NK1R)-immunoreactive (ir) neurons in the pre-Bötzinger complex (pre-BötC), the hypothesized kernel of normal respiratory rhythmogenesis. In the present study, we aimed to identify glutamatergic synapses onto NK1R-ir pre-BötC neurons, as excitatory synaptic transmission is a prerequisite to normal respiratory rhythmogenesis. Two types of vesicular glutamate transporters (VGLUT), VGLUT1 and VGLUT2, have been recently implicated in glutamate-mediated transmission. The present study used immunofluorescence and immunogold-silver staining to determine the relationship between the transporters and NK1R-ir neurons in the pre-BötC of adult rats. Under the confocal laser-scanning microscope, VGLUT2-ir boutons were found to be widely distributed in the pre-BötC, some of which were in close apposition to NK1R-ir somas and dendrites. VGLUT1-ir boutons were relatively rare and only a few were found to be in close apposition to NK1R-ir somas and dendrites. Electron microscopic observation revealed that approximately 41% of VGLUT2-ir terminals were in close apposition to, or made asymmetric synapses with NK1R-ir somas and dendrites in the pre-BötC. On the other hand, 50.5% of NK1R-ir dendrites were closely apposed to, or synapsed with VGLUT2-ir terminals. Occasionally, VGLUT1-ir terminals were found in close apposition to NK1R-ir somas or dendrites, but we were unable to identify synapses between them. The present findings provide the morphological basis for excitatory synaptic inputs onto NK1R-ir neurons in the pre-BötC. VGLUT2 may be involved in a dominant excitatory synaptic pathway for normal respiratory rhythmogenesis.
Liu
Ying-Ying
YY
Institute of Neurosciences, The Fourth Military Medical University, Xi'an 710032, China.
Wong-Riley
Margaret T T
MT
Liu
Jin-Ping
JP
Jia
Yi
Y
Liu
Hui-Ling
HL
Fujiyama
Fumino
F
Ju
Gong
G
D000818:Animals; D002352:Carrier Proteins / Q000032:analysis*; D003712:Dendrites / Q000737:chemistry / Q000648:ultrastructure; D005455:Fluorescent Antibody Technique; D018698:Glutamic Acid; D026901:Membrane Transport Proteins; D018613:Microscopy, Confocal; D016253:Microscopy, Immunoelectron; D009474:Neurons / Q000737:chemistry* / Q000648:ultrastructure*; D017729:Presynaptic Terminals / Q000737:chemistry / Q000648:ultrastructure; D051381:Rats; D017207:Rats, Sprague-Dawley; D018040:Receptors, Neurokinin-1 / Q000032:analysis*; D012119:Respiration; D012125:Respiratory Center / Q000737:chemistry* / Q000166:cytology; D013569:Synapses / Q000737:chemistry* / Q000648:ultrastructure*; D009435:Synaptic Transmission; D050598:Vesicular Glutamate Transport Protein 1; D050599:Vesicular Glutamate Transport Protein 2; D033921:Vesicular Transport Proteins
D002352:Carrier Proteins; D026901:Membrane Transport Proteins; D018040:Receptors, Neurokinin-1; C493475:Slc17a6 protein, rat; C493466:Slc17a7 protein, rat; D050598:Vesicular Glutamate Transport Protein 1; D050599:Vesicular Glutamate Transport Protein 2; D033921:Vesicular Transport Proteins; D018698:Glutamic Acid