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1 Department of Biology, Allegheny College, Meadville, Pennsylvania 16335; and 2 Department of Biology, St. Lawrence University, Canton, New York 13617
Glia are thought to
regulate ion homeostasis, including extracellular pH; however, their
role in modulating central CO2 chemosensitivity is
unclear. Using a push-pull cannula in chronically instrumented and conscious rats, we administered a glial toxin, fluorocitrate (FC; 1 mM) into the retrotrapezoid nucleus (RTN), a putative chemosensitive site, during normocapnia and hypercapnia. FC exposure significantly increased expired minute ventilation (
E) to a value
38% above the control level during normocapnia. During hypercapnia, FC
also significantly increased both breathing frequency and expired
E. During FC administration, maximal ventilation was
achieved at ~4% CO2, compared with 8-10%
CO2 during control hypercapnic trials. RTN perfusion of
control solutions had little effect on any ventilatory measures
(
E, tidal volume, or breathing frequency) during
normocapnic or hypercapnic conditions. We conclude that unilateral
impairment of glial function in the RTN of the conscious rat results in
stimulation of respiratory output.
brain stem pH regulation; central chemoreception; control of breathing; retrotrapezoid nucleus; brain stem glia
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