Sleep and respiratory patterns in the djungarian hamster

Abstract

Djungarian hamsters adapted to a 12 12 -h L/D photoperiod at 28 ± 1°C T amb, implanted with electroencephalogram and electromyogram electrodes and fitted with pneumomanometers were monitored for 4 h on 5 consecutive days to obtain baseline sleep stages and respiration in the nontorpid hamster. Fifty-seven percent of recording time was spent in the sleep state with rapid eye movement (REM) sleep occupying 11% of the total sleep time. An analysis of successive 30-min epochs revealed that REM percentage and REM period (REMP) frequency in the first 30 min were significantly ( p<0.0001) lower compared to the last 150 min, while REMP duration remained unchanged throughout the recording session. Respiratory frequency was significantly higher ( p<0.01) by 24% in REM sleep as compared to Non-REM sleep. The euthermic sleep pattern in the nontorpid Djungarian hamster, adapted to a steady-state photoperiod, contained alternating periods of non-rapid eye movement (Non-REM) and REM sleep, similar to that seen in other rodents. REM sleep pattern regulation became steady after the initial 90-min transition period during which REM frequency but not duration increased. This transition to a steady REM sleep pattern might allow flexibility in entering the torpor state during the presence of unfavorable environmental stimuli.