Effects of the lesions of the suprachiasmatic nuclei and light-dark phase inversed exercise on asthmatic responses in rats

The present study was carried out to investigate the change of antigen-induced asthmatic responses after organic and functional disorders of diurnal variations in rats of the asthma model. The organic disappearance of diurnal locomotor fluctuations was produced by electrolytic lesions of the suprachiasmatic nuclei (SCN), and functional disturbance of them was attempted by a wheel running exercise during either a light or dark phase. Plasma histamine levels at immediate asthmatic response and infiltrating eosinophils in the lamina propria mucosae of the left main bronchus during late asthmatic response in SCN lesioned rats were lower than in pseudo lesioned and control rats, respectively. These immediate and late asthmatic responses in the exercising group during the light phase were stronger compared to the exercising group during the dark phase. The experimental loss of diurnal fluctuations protect rats from worsening asthmatic responses. However, light-dark phase inversed exercise, which may cause a disturbance in circadian rhythms clinically, appears to contribute to the worsening of asthmatic responses.