Journal of Applied Physiology, Vol 38, Issue 4 688-695, Copyright © 1975 by American Physiological Society
Effects of CO-2 and extracellular H+ iontophoresis on single cell activity in the cat brainstem
P. L. Marino and T. W. Lamb
The activity of single cells in deep regions of the medulla oblongata was
observed both during CO2 inhalation and during the extracellular
iontophoresis of hydrogen ions in peripheral chemoreceptor-denervated cats.
All 53 neurons that fired in synchrony with some part of the ventilatory
cycle showed increased firing during CO2 inhalation; yet none responded in
a graded fashion to the extracellular application of hydrogen ions.
Seventy-one of the 74 nonperiodic cells studied showed no response to CO2
inhalation. Of the 3 nonperiodic cells that did respond to CO2, 2 also
responded in a graded fashion to the extracellular iontophoresis of
hydrogen ions. It is concluded that the cell bodies of medullary neurons
with respiratory periodicity are relatively insensitive to hydrogen ions.
Further the paucity of hydrogen ion-sensitive cells found in deep areas of
the medulla does not support the notion that medullary hydrogen ion
chemoreception is largely achieved by structures located deep in the lower
brainstem.
