Breathing and respiratory response to CO2 were observed in 6 awake cats and 1 control before and after bilateral coagulation of the formerly described area S (Schläfke and Loeschcke, 1967) on the ventral medullary surface under hyperoxic conditions. Ventilation decreased,PCO2 rose and CO2 response was almost or completely abolished in 4 cats, and moderately reduced in 2 cats. Inhalation of CO2 had an inhibitory effect on ventilation in two cases. In some instances the respiratory frequency was increased by CO2. Periodic breathing as well as spotaneous hyperventilatron elicited by ‘arousal’ indicate parallels to the Pickwickian or Ondine's curse syndrome. No respiratory changes were produced by a lesion on the pyramidal tract medial to the area S. It is concluded that central chemosensitivity can be eliminated within the superficial layer of the area S. The loss of CO2 response seems to be correlated with complete destruction of the superficial nerve cells located within the area S (Petrovický, 1968) and degeneration within the ventral part of the nucleus paragigantocellularis.
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