Sleep changes in long-term fasting geese in relation to lipid and protein metabolism

The proportion and the distribution over 24 h of the different arousal stages characterized in geese--wakefulness (W), drowsiness (D), and slow-wave (SWS) and paradoxical sleep (PS)--were studied in caged birds when fed and then fasted during about 40 days. In both the fed and fasted state, each arousal stage was distributed through numerous episodes of a short duration. The geese slept a little more during the night than during the day, a difference that was moderately emphasized during the fast. Fasting induced only a slight decrease in W. There were important changes in SWS and D in relation to the periods of fasting that were previously found to correspond to changes in lipid and protein utilization. When proteins were spared and lipids accounted for most of the energy expenditure, the fasted geese went more and more rapidly from W to SWS (proportion of D decreased from 33 to 13%/day) and slept for progressively longer periods (SWS increased from 23 to 49%/day). By contrast, when protein utilization rose, the general trend in sleep was a decrease in SWS and an increase in D. During the fast, changes in PS were in the same proportion as those in SWS. These reactions are examined for their implications in energy-saving and sleep mechanisms.