Circadian periodicity in the duration of decapitation-induced gasping in mice

The circadian variation of decapitation-induced gasping was investigated by measuring the gasping duration of isolated mouse head after decapitation under both normal and restricted feeding conditions. In the normally fed mice, there was a circadian periodicity in the gasping duration: it was longer during the light period than during the dark period. The circadian periodicity was completely reversed by the restriction of food. The circadian periodicity of the gasping duration were conversely parallel to those of body temperature in both normal and feeding restricted mice, and regression analysis revealed a negative correlation between the gasping duration and body temperature. Furthermore, pentobarbital and ethanol, agents that caused hypothermia, markedly prolonged the gasping duration. These findings suggest that there is a circadian periodicity in the brain reactivity after complete ischemia, which may be associated with the changes of body temperature.