Elimination of central chemosensitivity by coagulation of a bilateral area on the ventral medullary surface in awake cats

Abstract

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.