Chronic caffeine teatment disrupts circadian rhythm in Drosophila
Authors: Aishwarya Segu; Nisha Kannan
Affiliation: Indian Institute of Science Education and Research, Thiruvananthapuram
Keywords: h. circadian rhythms and sleep; a. stress responses
The circadian clock governs the timing of sleep-wake cycles as well as of other behavioural, physiological and metabolic processes. While the endogenous circadian clock mediates the timing of sleep, homeostatic mechanisms modulate the amount and depth of sleep. Evidence from previous studies showed that caffeine intake promotes wakefulness, whereas adult-stage specific caffeine treatment not only suppresses sleep but also delays the phase of circadian rhythm in Drosophila. In humans, caffeine is consumed on a daily basis and hence it is important to understand the effect of prolonged intake of caffeine on circadian and homeostatic regulation of sleep. In the present study we examined the differential effect of acute and chronic caffeine treatment on sleep ontogeny as well as on circadian and homeostatic regulation of sleep in Drosophila. The results of our study showed that acute caffeine treatment reduces both day and night sleep in mature flies whereas it reduced only the day sleep in young flies. Chronic caffeine treatment did not exert any significant effect on sleep in young flies. On the other hand, it delayed the timing of sleep in mature flies and in addition these flies reduced the morning and evening anticipatory activity at higher caffeine concentration under 12 hour: 12 hour light: dark cycles. Apart from these it also changed the overt rhythm of these flies. These flies exhibited either a longer free running period or arrhythmicity under constant darkness. The results from our study shows that acute treatment of caffeine reduces sleep in flies and does not affect the homeostatic sleep whereas prolonged caffeine treatment affects the overt rhythm of the flies including the eclosion rhythm.