Neurokinin-1 receptor-immunoreactive neurons of the ventral respiratory group in the rat.
The rostral end of the ventral respiratory group (VRG) contains neurons that are intensely neurokinin-1 receptor (NK1R) immunoreactive (ir). It has been theorized that some of these cells might be critical to respiratory rhythmogenesis (Gray et al. [1999] Science 286:1566-1568). In the present study we determined what major transmitter these NK1R-ir cells make and whether they are bulbospinal or propriomedullary. NK1R-ir neurons were found in the VRG between Bregma levels -11.7 and -13.6 mm. The highest concentration was found between Bregma -12.3 and -13.0 mm. This region overlaps with the pre-Bötzinger complex (pre-BötC) as it was found to contain many pre-inspiratory neurons, few E2-expiratory neurons, and no I-incremental neurons. VRG NK1R-ir neurons contain neither tyrosine hydroxylase (TH) nor choline acetyl-transferase (ChAT) immunoreactivity, although dual-labeled neurons were found elsewhere within the rostral medulla. GAD67 mRNA was commonly detected in the ventrolateral medulla (VLM) but rarely in the NK1R-ir neurons of the pre-BötC region (6 % of somatic profiles). GlyT2 mRNA was commonly found in the pre-BötC region but rarely within NK1R-ir neurons (1.3 %). Up to 40% of VRG NK1R-ir neurons were retrogradely labeled by Fluoro-Gold (FG) injected in the contralateral pre-BötC region. Some NK1R-ir VRG neurons located caudal to Bregma -12.6 mm were retrogradely labeled by FG injected in the spinal cord (C4-C5, T2-T4). In sum, NK1R immunoreactivity is present in many types of ventral medullary neurons. Within the VRG proper, NK1R-ir neurons are concentrated in an area that overlaps with the pre-BötC. Within this limited region of the VRG, NK1R-ir neurons are neither cholinergic nor catecholaminergic, and very few are gamma-aminobutyric acid (GABA)ergic or glycinergic. The data suggest that most NK1R-ir neurons of the pre-BötC region are excitatory. Furthermore, the more rostral NK1R-ir cells are propriomedullary, whereas some of the caudal ones project to the spinal cord.
Wang
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Department of Pharmacology, University of Virginia, Charlottesville, Virginia 22908, USA.
Stornetta
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Rosin
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Guyenet
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D000109:Acetylcholine / Q000378:metabolism; D000200:Action Potentials / Q000502:physiology; D026921:Amino Acid Transport Systems, Neutral; D000818:Animals; D002352:Carrier Proteins / Q000235:genetics; D002395:Catecholamines / Q000378:metabolism; D002795:Choline O-Acetyltransferase / Q000378:metabolism; D004525:Efferent Pathways / Q000166:cytology / Q000378:metabolism; D005456:Fluorescent Dyes / Q000493:pharmacokinetics; D005968:Glutamate Decarboxylase / Q000235:genetics; D050487:Glycine Plasma Membrane Transport Proteins; D007150:Immunohistochemistry; D007527:Isoenzymes / Q000235:genetics; D008297:Male; D008526:Medulla Oblongata / Q000166:cytology / Q000378:metabolism*; D009474:Neurons / Q000166:cytology / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley / Q000033:anatomy & histology / Q000378:metabolism*; D018040:Receptors, Neurokinin-1 / Q000378:metabolism*; D012125:Respiratory Center / Q000166:cytology / Q000378:metabolism*; D012143:Respiratory Physiological Phenomena; D013116:Spinal Cord / Q000166:cytology / Q000378:metabolism; D013266:Stilbamidines; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism
C049774:2-hydroxy-4,4'-diamidinostilbene, methanesulfonate salt; D026921:Amino Acid Transport Systems, Neutral; D002352:Carrier Proteins; D002395:Catecholamines; D005456:Fluorescent Dyes; D050487:Glycine Plasma Membrane Transport Proteins; D007527:Isoenzymes; D012333:RNA, Messenger; D018040:Receptors, Neurokinin-1; C493269:Slc6a5 protein, rat; D013266:Stilbamidines; D014446:Tyrosine 3-Monooxygenase; D002795:Choline O-Acetyltransferase; D005968:Glutamate Decarboxylase; C402565:glutamate decarboxylase 1; D000109:Acetylcholine