title: Role of parafacial nuclei in control of breathing in adult rats.
abstract: Contiguous brain regions associated with a given behavior are increasingly being divided into subregions associated with distinct aspects of that behavior. Using recently developed neuronal hyperpolarizing technologies, we functionally dissect the parafacial region in the medulla, which contains key elements of the central pattern generator for breathing that are important in central CO2-chemoreception and for gating active expiration. By transfecting different populations of neighboring neurons with allatostatin or HM4D Gi/o-coupled receptors, we analyzed the effect of their hyperpolarization on respiration in spontaneously breathing vagotomized urethane-anesthetized rats. We identify two functionally separate parafacial nuclei: ventral (pFV) and lateral (pFL). Disinhibition of the pFL with bicuculline and strychnine led to active expiration. Hyperpolarizing pFL neurons had no effect on breathing at rest, or changes in inspiratory activity induced by hypoxia and hypercapnia; however, hyperpolarizing pFL neurons attenuated active expiration when it was induced by hypercapnia, hypoxia, or disinhibition of the pFL. In contrast, hyperpolarizing pFV neurons affected breathing at rest by decreasing inspiratory-related activity, attenuating the hypoxia- and hypercapnia-induced increase in inspiratory activity, and when present, reducing expiratory-related abdominal activity. Together with previous observations, we conclude that the pFV provides a generic excitatory drive to breathe, even at rest, whereas the pFL is a conditional oscillator quiet at rest that, when activated, e.g., during exercise, drives active expiration.
authors.affiliation: Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angles, Los Angeles, California 90095-1763.
authors.forename: Robert T R
authors.initials: RT
authors.lastname: Huckstepp
authors.affiliation: Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angles, Los Angeles, California 90095-1763.
authors.forename: Kathryn P
authors.initials: KP
authors.lastname: Cardoza
authors.affiliation: Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angles, Los Angeles, California 90095-1763.
authors.forename: Lauren E
authors.initials: LE
authors.lastname: Henderson
authors.affiliation: Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angles, Los Angeles, California 90095-1763 feldman@ucla.edu.
authors.forename: Jack L
authors.identifier: http://orcid.org/0000-0003-3692-9412
authors.initials: JL
authors.lastname: Feldman
mesh_terms: D000818:Animals; D008526:Medulla Oblongata / Q000502:physiology*; D009474:Neurons / Q000502:physiology*; D051381:Rats; D012119:Respiration; D012125:Respiratory Center / Q000502:physiology*
keywords: active expiration; control of breathing; expiratory oscillator; parafacial respiratory group; respiration; retrotrapezoid nucleus