HYPERCAPNIA INDUCES C-FOS EXPRESSION IN NEURONS OF RETROTRAPEZOID NUCLEUS IN CATS

To investigate which neurons in the medulla oblongata produced the nuc lear protein FOS during stimulation of respiration by hypercapnia, we subjected six anaesthetized cats to 10% CO2 in air for one hour. Four animals inhaled room air. Coronal sections from the medulla oblongata were processed for FOS immunohistochemistry. Only the retrotrapezoid n ucleus (RTN) of the animals exposed to CO2 contained a large populatio n of labelled neurons. This indicates that RTN neurons are strongly ac tivated during hypercapnia.