Ventilatory effects of impaired glial function in a brain stem chemoreceptor region in the conscious rat.
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 (VE) to a value 38% above the control level during normocapnia. During hypercapnia, FC also significantly increased both breathing frequency and expired VE. During FC administration, maximal ventilation was achieved at approximately 4% CO2, compared with 8-10% CO2 during control hypercapnic trials. RTN perfusion of control solutions had little effect on any ventilatory measures (VE, 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.
Department of Biology, Allegheny College, Meadville, Pennsylvania 16335, USA.
J
J
Holleran
M
M
Babbie
J S
JS
Erlichman
D000818:Animals; D001933:Brain Stem / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D002245:Carbon Dioxide / Q000097:blood / Q000502:physiology; D002529:Cerebellar Nuclei / Q000502:physiology; D002628:Chemoreceptor Cells / Q000187:drug effects / Q000502:physiology*; D002951:Citrates / Q000633:toxicity; D005260:Female; D006863:Hydrogen-Ion Concentration; D008297:Male; D009457:Neuroglia / Q000187:drug effects / Q000502:physiology*; D010991:Plethysmography; D051381:Rats; D017207:Rats, Sprague-Dawley; D015656:Respiratory Mechanics / Q000187:drug effects / Q000502:physiology*
D002951:Citrates; D002245:Carbon Dioxide; C007744:fluorocitrate