Arrest of the circadian pacemaker driving the pineal melatonin rhythm in hibernating golden hamsters, Mesocricetus auratus

The circadian clock stops ticking during deep hibernation in the European hamster

“…This finding was confirmed at the melatonin level (Fig. 3B), although plasma melatonin concentrations were continuously low during torpor bouts (for all conditions of hibernation, P Ͼ 0.05 versus euthermic D and SD), as already described in other species (15)(16)(17). Interestingly, the plasma melatonin level has been reported to rise rapidly after arousal from hibernation, whatever the time of arousal (15,16).…”

“…3B), although plasma melatonin concentrations were continuously low during torpor bouts (for all conditions of hibernation, P Ͼ 0.05 versus euthermic D and SD), as already described in other species (15)(16)(17). Interestingly, the plasma melatonin level has been reported to rise rapidly after arousal from hibernation, whatever the time of arousal (15,16). The fact that Aa-nat mRNA levels remain persistently elevated during hibernation may well explain these observations and suggests a possible uncoupling between transcriptional activity and protein synthesis/enzymatic function.…”

The circadian clock stops ticking during deep hibernation in the European hamster

“…This finding was confirmed at the melatonin level (Fig. 3B), although plasma melatonin concentrations were continuously low during torpor bouts (for all conditions of hibernation, P Ͼ 0.05 versus euthermic D and SD), as already described in other species (15)(16)(17). Interestingly, the plasma melatonin level has been reported to rise rapidly after arousal from hibernation, whatever the time of arousal (15,16).…”

“…3B), although plasma melatonin concentrations were continuously low during torpor bouts (for all conditions of hibernation, P Ͼ 0.05 versus euthermic D and SD), as already described in other species (15)(16)(17). Interestingly, the plasma melatonin level has been reported to rise rapidly after arousal from hibernation, whatever the time of arousal (15,16). The fact that Aa-nat mRNA levels remain persistently elevated during hibernation may well explain these observations and suggests a possible uncoupling between transcriptional activity and protein synthesis/enzymatic function.…”

Seasonal change in the temporal organization of wheel-running activity of the European Hamster,Cricetus cricetus

“…During the latter half of the year, short bouts of activity were found to be randomly distributed over the 24-h period of a day. A similar loss of circadian rhythmicity at the beginning of the hibernation season has been described for locomotor activity in the Turkish hamster [15] and for pineal 422 melatonin formation in the golden hamster [16] . A complete loss of the pineal melatonin rhythm has also been reported for the European hamster, however, in this case occurring during late summer (17].…”

Gene expression profiling during hibernation in the European hamster

“…Studies in various hibernating species report no night-time increase in melatonin during the torpor states, due to SCN clock arrest, with a subsequent rapid restoration of the nocturnal rhythm upon arousal 30,56–58 . Studies investigating changes in 2- 125 I-iodomelatonin binding on melatonin receptor density during hibernation in the brains of hedgehogs 59 and ground squirrels 60 have reported decreased numbers of binding sites in the pars tuberalis during torpor compared to normothermia.…”

The circadian clock stops ticking during deep hibernation in the European hamster

“…This finding was confirmed at the melatonin level (Fig. 3B), although plasma melatonin concentrations were continuously low during torpor bouts (for all conditions of hibernation, P Ͼ 0.05 versus euthermic D and SD), as already described in other species (15)(16)(17). Interestingly, the plasma melatonin level has been reported to rise rapidly after arousal from hibernation, whatever the time of arousal (15,16).…”

“…3B), although plasma melatonin concentrations were continuously low during torpor bouts (for all conditions of hibernation, P Ͼ 0.05 versus euthermic D and SD), as already described in other species (15)(16)(17). Interestingly, the plasma melatonin level has been reported to rise rapidly after arousal from hibernation, whatever the time of arousal (15,16). The fact that Aa-nat mRNA levels remain persistently elevated during hibernation may well explain these observations and suggests a possible uncoupling between transcriptional activity and protein synthesis/enzymatic function.…”

Seasonal change in the temporal organization of wheel-running activity of the European Hamster,Cricetus cricetus

“…During the latter half of the year, short bouts of activity were found to be randomly distributed over the 24-h period of a day. A similar loss of circadian rhythmicity at the beginning of the hibernation season has been described for locomotor activity in the Turkish hamster [15] and for pineal 422 melatonin formation in the golden hamster [16] . A complete loss of the pineal melatonin rhythm has also been reported for the European hamster, however, in this case occurring during late summer (17].…”

Gene expression profiling during hibernation in the European hamster

“…Studies in various hibernating species report no night-time increase in melatonin during the torpor states, due to SCN clock arrest, with a subsequent rapid restoration of the nocturnal rhythm upon arousal 30,56–58 . Studies investigating changes in 2- 125 I-iodomelatonin binding on melatonin receptor density during hibernation in the brains of hedgehogs 59 and ground squirrels 60 have reported decreased numbers of binding sites in the pars tuberalis during torpor compared to normothermia.…”

The circadian clock stops ticking during deep hibernation in the European hamster

“…This finding was confirmed at the melatonin level (Fig. 3B), although plasma melatonin concentrations were continuously low during torpor bouts (for all conditions of hibernation, P Ͼ 0.05 versus euthermic D and SD), as already described in other species (15)(16)(17). Interestingly, the plasma melatonin level has been reported to rise rapidly after arousal from hibernation, whatever the time of arousal (15,16).…”

“…3B), although plasma melatonin concentrations were continuously low during torpor bouts (for all conditions of hibernation, P Ͼ 0.05 versus euthermic D and SD), as already described in other species (15)(16)(17). Interestingly, the plasma melatonin level has been reported to rise rapidly after arousal from hibernation, whatever the time of arousal (15,16). The fact that Aa-nat mRNA levels remain persistently elevated during hibernation may well explain these observations and suggests a possible uncoupling between transcriptional activity and protein synthesis/enzymatic function.…”

Seasonal change in the temporal organization of wheel-running activity of the European Hamster,Cricetus cricetus

“…During the latter half of the year, short bouts of activity were found to be randomly distributed over the 24-h period of a day. A similar loss of circadian rhythmicity at the beginning of the hibernation season has been described for locomotor activity in the Turkish hamster [15] and for pineal 422 melatonin formation in the golden hamster [16] . A complete loss of the pineal melatonin rhythm has also been reported for the European hamster, however, in this case occurring during late summer (17].…”

Gene expression profiling during hibernation in the European hamster

“…Studies in various hibernating species report no night-time increase in melatonin during the torpor states, due to SCN clock arrest, with a subsequent rapid restoration of the nocturnal rhythm upon arousal 30,56–58 . Studies investigating changes in 2- 125 I-iodomelatonin binding on melatonin receptor density during hibernation in the brains of hedgehogs 59 and ground squirrels 60 have reported decreased numbers of binding sites in the pars tuberalis during torpor compared to normothermia.…”