Distribution of bulbospinal gamma-aminobutyric acid-synthesizing neurons of the ventral respiratory group of the rat.
Spinal respiratory motoneuron activity is controlled primarily by excitatory and inhibitory neurons in the medulla oblongata. To identify bulbospinal inhibitory neurons, immunohistochemistry for glutamic acid decarboxylase (GAD) was combined with retrograde labeling of projections to the C(4) ventral horn with Fluoro-Gold. GAD-immunoreactive bulbospinal neurons were located in the ventrolateral portion of the intermediate reticular nucleus, the ventral portion of the medial reticular nuclei, and the raphe and spinal vestibular nuclei. Small numbers of bulbospinal ventral respiratory group neurons were GAD immunoreactive. These neurons were distributed throughout the rostral ventral respiratory group and the Bötzinger complex. Surprisingly, low numbers of Bötzinger neurons, a population thought to be exclusively inhibitory, were GAD immunoreactive. These results suggest that the rostral ventral respiratory group and the Bötzinger complex both contain heterogeneous bulbospinal neuron populations, only some of which have gamma-aminobutyric acid (GABA)-mediated inhibitory control over phrenic motoneurons. Furthermore, the ventral respiratory group contained many GABAergic neurons that lacked bulbospinal projections.
Department of Anatomy and Neurobiology, Faculty of Medicine, Dalhousie University, Halifax, Nova Scotia B3H 4H7, Canada. howarde@is.dal.ca
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D000818:Animals; D003078:Colchicine; D005456:Fluorescent Dyes; D005968:Glutamate Decarboxylase / Q000032:analysis*; D008297:Male; D008526:Medulla Oblongata / Q000166:cytology; D009046:Motor Neurons / Q000502:physiology; D009415:Nerve Net / Q000166:cytology; D009419:Nerve Tissue Proteins / Q000032:analysis*; D009474:Neurons / Q000378:metabolism*; D010791:Phrenic Nerve / Q000502:physiology; D011903:Raphe Nuclei / Q000502:physiology / Q000648:ultrastructure; D051381:Rats; D017207:Rats, Sprague-Dawley; D012125:Respiratory Center / Q000166:cytology* / Q000378:metabolism; D012132:Respiratory Muscles / Q000294:innervation*; D013116:Spinal Cord / Q000166:cytology*; D013266:Stilbamidines; D014726:Vestibular Nuclei / Q000502:physiology / Q000648:ultrastructure; D005680:gamma-Aminobutyric Acid / Q000096:biosynthesis*
C049774:2-hydroxy-4,4'-diamidinostilbene, methanesulfonate salt; D005456:Fluorescent Dyes; D009419:Nerve Tissue Proteins; D013266:Stilbamidines; D005680:gamma-Aminobutyric Acid; D005968:Glutamate Decarboxylase; D003078:Colchicine