Evidence for oxygen and carbon dioxide receptors in insect CNS influencing ventilation

Ventilatory efferent discharges in the isolated central nervous system (CNS) of the lubber grasshopper Taeniopoda eques were recorded and the change of ventilatory rates were measured in correlation to changing concentrations of oxygen and carbon dioxide. These in vitro responses were compared to the ventilatory rates of intact animals exposed to various gas tensions. We found highly significant effects of oxygen on the ventilatory response of both the in vitro CNS and the intact animals, with ventilatory rates inverse to the concentration of oxygen. Application of changing carbon dioxide concentrations showed significant effects on ventilatory frequencies in isolated CNS of the American desert locust (Schistocerca americana). Our results provide the first direct evidence for the existence of oxygen and carbon dioxide receptors located in the insect CNS. (C) 2002 Elsevier Science Inc. All rights reserved.