title: CO2-sensitive neurons in organotypic cultures of the fetal rat medulla.
abstract: Medullary slices of the fetal rat at gestational day 16 were cultivated (organotypic culture) for up to 20 days and current clamp experiments were performed on outgrowing neurons. CO2-sensitivity was tested by changing the P(CO2) in the bath solution (equilibrating CO2 fraction from 0.02 to 0.09). Two groups of CO2-sensitive neurons were found; one with and the other without intrinsic CO2-chemosensitivity. Neurons with intrinsic CO2-sensitivity maintained their spontaneous activity and chemosensitivity after blockade of synaptic transmission. These neurons exhibited action potentials that were preceeded by a spontaneous interspike depolarization and followed by an afterhyperpolarization (beating neurons). Increasing P(CO2) either decreased (inhibited neurons, n = 55) or increased the spike frequency of these neurons (stimulated neurons, n = 31). The reduced activity of CO2-inhibited neurons was associated with membrane hyperpolarization and/or decreases in the slope of interspike depolarization. In contrast CO2-stimulated neurons were depolarized and the slope of their interspike depolarization was augmented during acidosis. In addition, we demonstrated a strong voltage dependence of CO2-induced effects on membrane potential and spike frequency. Neurons with non-beating activity did not show a spontaneous interspike depolarization and their spike generation and CO2-sensitivity appeared to be entirely produced through synaptic inputs. The CO2-mediated changes in electrical properties of these neurons closely resemble those of various CNS neurons, including respiratory neurons, in whole animal or neonatal brainstem-spinal cord preparations.
authors.affiliation: Institut für Physiologie, Ruhr-Universität Bochum, Germany.
authors.forename: M C
authors.initials: MC
authors.lastname: Wellner-Kienitz
authors.forename: H
authors.initials: H
authors.lastname: Shams
mesh_terms: D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000818:Animals; D002245:Carbon Dioxide / Q000494:pharmacology*; D046508:Culture Techniques; D004351:Drug Resistance; D004594:Electrophysiology; D005260:Female; D005333:Fetus / Q000187:drug effects / Q000502:physiology; D008526:Medulla Oblongata / Q000166:cytology / Q000187:drug effects* / Q000502:physiology*; D009474:Neurons / Q000187:drug effects / Q000502:physiology; D018408:Patch-Clamp Techniques; D011247:Pregnancy; D051381:Rats; D017207:Rats, Sprague-Dawley; D015656:Respiratory Mechanics / Q000187:drug effects / Q000502:physiology; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology
chemical_list: D002245:Carbon Dioxide