title: Synaptic relationship between somatostatin- and neurokinin-1 receptor-immunoreactive neurons in the pre-Bötzinger complex of rats.
abstract: The pre-Bötzinger complex (pre-BötC) in the ventrolateral medulla oblongata is critical for the generation of respiratory rhythm in mammals. Somatostatin (SST) and neurokinin 1 receptor (NK1R) immunoreactivity have been used as markers of the pre-BötC. SST immunoreactivity almost completely overlaps with small fusiform NK1R-immunoreactive (ir) neurons, the presumed rhythmogenic neurons, but not with large multipolar NK1R-ir neurons. Understanding the neurochemical characteristics, especially the synaptic relationship of SST/NK1R-ir neurons within the pre-BötC network is essential in providing cellular and structural bases for understanding their physiological significance. This work has not been documented so far. We found that SST immunoreactivity was highly expressed in terminals, somas, and primary dendrites in the pre-BötC. Besides the small fusiform neurons, a small population of medium-sized NK1R-ir neurons also colocalized with SST. Large NK1R-ir neurons were not SST-ir, but received somatostatinergic inputs. SST-ir terminals were glutamatergic or GABAergic, and synapsed with NK1R-ir neurons. Most of synapses between them were of the symmetric type, indicating their inhibitory nature. Asymmetric synapses were evident between SST-ir terminals and NK1R-ir dendrites, strongly suggesting an excitatory innervation from the presumed rhythmogenic neurons as these neurons are glutamatergic. We speculate that SST-mediated excitatory and inhibitory synaptic transmission onto NK1R-ir rhythmogenic and follower neurons synchronizes their activity to contribute to respiratory rhythmogenesis and control.
authors: Institute of Neurosciences, The Fourth Military Medical University, Xi'an, China.
authors: Xiao-Yan
authors: XY
authors: Wei
authors: Yu
authors: Y
authors: Zhao
authors: Margaret T T
authors: MT
authors: Wong-Riley
authors: Gong
authors: G
authors: Ju
authors: Ying-Ying
authors: YY
authors: Liu
mesh_terms: D000818:Animals; D005968:Glutamate Decarboxylase / Q000378:metabolism; D050487:Glycine Plasma Membrane Transport Proteins / Q000378:metabolism; D008297:Male; D016253:Microscopy, Immunoelectron; D009474:Neurons / Q000378:metabolism* / Q000648:ultrastructure; D051381:Rats; D017207:Rats, Sprague-Dawley; D018040:Receptors, Neurokinin-1 / Q000378:metabolism* / Q000648:ultrastructure; D012125:Respiratory Center / Q000166:cytology*; D013004:Somatostatin / Q000378:metabolism*; D013569:Synapses / Q000000981:diagnostic imaging / Q000378:metabolism*; D014463:Ultrasonography; D050599:Vesicular Glutamate Transport Protein 2 / Q000378:metabolism
chemical_list: D050487:Glycine Plasma Membrane Transport Proteins; D018040:Receptors, Neurokinin-1; D050599:Vesicular Glutamate Transport Protein 2; D013004:Somatostatin; D005968:Glutamate Decarboxylase