CO2-inhibited neurons in the medullary raphé are GABAergic

Respir Physiol Neurobiol. 2014 Nov 1;203:28-34. doi: 10.1016/j.resp.2014.07.016. Epub 2014 Aug 1.

Abstract

Previous studies have reported subsets of medullary raphé neurons that are either stimulated or inhibited by CO2/pH in vitro, in situ, and in vivo. We tested the hypothesis that medullary raphé CO2-inhibited neurons are GABAergic. Extracellular recordings in unanesthetized juvenile in situ rat preparations showed reversible hypercapnia-induced suppression of 19% (63/323) of medullary raphé neurons, and this suppression persisted after antagonism of NMDA, AMPA/kainate, and GABAA receptors. We stained a subset of CO2-inhibited cells and found that most (11/12) had glutamic acid decarboxylase 67 immunoreactivity (GAD67-ir). These data indicate that the majority of acidosis-inhibited medullary raphé neurons are GABAergic, and that their chemosensitivity is independent of major fast synaptic inputs. Thus, CO2-sensitive GABAergic neurons may play a role in central CO2/pH chemoreception.

Keywords: Breathing; Chemosensitivity; GABA; Raphé.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • 6-Cyano-7-nitroquinoxaline-2,3-dione / pharmacology
  • Action Potentials / drug effects
  • Animals
  • Animals, Newborn
  • Bicuculline / pharmacology
  • Biotin / analogs & derivatives
  • Biotin / metabolism
  • Carbon Dioxide / pharmacology*
  • Dose-Response Relationship, Drug
  • Excitatory Amino Acid Antagonists / pharmacology
  • GABA Antagonists / pharmacology
  • GABAergic Neurons / drug effects*
  • Glutamate Decarboxylase / metabolism
  • In Vitro Techniques
  • Male
  • Midbrain Raphe Nuclei / cytology*
  • Patch-Clamp Techniques
  • Piperazines / pharmacology
  • Rats
  • Rats, Sprague-Dawley
  • Tryptophan Hydroxylase / metabolism
  • gamma-Aminobutyric Acid / metabolism*

Substances

  • Excitatory Amino Acid Antagonists
  • GABA Antagonists
  • Piperazines
  • Carbon Dioxide
  • gamma-Aminobutyric Acid
  • biotinamide
  • 6-Cyano-7-nitroquinoxaline-2,3-dione
  • Biotin
  • 3-(2-carboxypiperazin-4-yl)propyl-1-phosphonic acid
  • Tryptophan Hydroxylase
  • Glutamate Decarboxylase
  • glutamate decarboxylase 1
  • Bicuculline