Abolition of a viscerosomatic reflex during oxygen deprivation

Effect of hypoxia was studied on the J reflex, a term used for the reflex inhibition of muscular exercise by activation of type J pulmonary endings. Hypoxia was induced by ventilating the animal with gas mixtures varying from 18 to 9% oxygen in nitrogen. The blood gas tensions of the arterial blood (PaO2) were measured before, during, and after hypoxia. It was found that the J reflex is sensitive to a reduction in oxygen. A fall in PaO2 between 67 and 47 Torr abolished this reflex. Studies were also undertaken to exclude the possibility that the effect of hypoxia was predominantly exerted on monosynaptic reflex itself. A similar fall in PaO2 also depressed the monosynaptic reflex. Minimum time required for the significant depression was 32 s. On the contrary the J reflex was abolished within this period suggesting that the abolition of J reflex is independent of the changes in monosynaptic reflex during hypoxia.