title: Efferent projections of pulmonary rapidly adapting receptor relay neurons in the cat.
abstract: Axonal projections of second order neurons activated by vagal afferent fibers originating from pulmonary rapidly adapting receptors (RARs) were studied electrophysiologically in Nembutal-anesthetized, paralyzed and artificially ventilated cats. Extracellular recordings from these neurons (referred to as 'RAR-cells') were made in the commissural subnucleus (COM) of the nucleus of the solitary tract (NTS). They were identified by a combination of stimuli including stimulation of the vagus nerve(s), hyperinflation and deflation of the lungs, and a brief period of ammonia vapor inhalation. A total of 80 RAR-cells were tested for axonal projections to a respiration-related area in the brain-stem, either the dorsolateral rostral pons or the dorsal respiratory group (DRG) or the ventral respiratory group (VRG) or the Bötzinger complex (BOT) and/or the spinal cord. Twenty-two of the 47 (47%) RAR-cells tested for ipsilateral pontine projection could be antidromically activated, and in 8 cases evidence for axonal arborization was obtained. Only 1 of the 11 RAR-cells tested for DRG projection, and 1 of the 10 RAR-cells tested for VRG projection, were antidromically activated. No RAR-cells were activated from the BOT (n = 8) or from the C3-C4 segments of the spinal cord (n = 11). Bilateral lesions of the COM abolished the reflex responses induced by ammonia inhalation or hyperinflation of the lungs, but not the Hering-Breuer reflex. These results indicate that a pathway from the COM to the rostral pons forms part of the reflex arc originating from RARs.
authors.affiliation: Department of Neurobiology, Tokyo Metropolitan Institute for Neurosciences, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Ezure
authors.forename: K
authors.initials: K
authors.lastname: Otake
authors.forename: J
authors.initials: J
authors.lastname: Lipski
authors.forename: R B
authors.initials: RB
authors.lastname: She
mesh_terms: D000818:Animals; D001369:Axons / Q000502:physiology; D002415:Cats; D004558:Electric Stimulation; D008168:Lung / Q000294:innervation*; D008526:Medulla Oblongata / Q000166:cytology / Q000502:physiology; D009434:Neural Pathways / Q000166:cytology / Q000502:physiology; D009476:Neurons, Efferent / Q000502:physiology*; D011149:Pons / Q000502:physiology; D013238:Stereotaxic Techniques; D014630:Vagus Nerve / Q000502:physiology