Comparative effects of melatonin, zolpidem and diazepam on sleep, body temperature, blood pressure and heart rate measured by radiotelemetry in Wistar rats.
BACKGROUND
The role of melatonin (MLT) in mediating the sleep-wake cycle has been previously suspected of indicating that this substance could be a candidate for a new generation of hypnotics.


OBJECTIVE
We investigated whether MLT acted as a sleep promoter or a modulator of sleep temporal timing related to cardiovascular and body temperature (Tb) adaptations to sleep induction. The pharmacological effects of MLT on sleep were compared with zolpidem (ZP) and diazepam (DZ).


METHODS
The radiotelemetry system was used to record the electrocorticogram [slow wave sleep (SWS), paradoxical sleep (PS)], Tb, blood pressure and heart rate in six Wistar rats. DZ (3 mg/kg and 6 mg/kg), ZP (1, 3, 5 and 10 mg/kg) and MLT (2.5 and 5 mg/kg) were delivered intraperitoneally during light (L) and dark (D) periods.


RESULTS
MLT increased the number of sleep cycles (L: 30%, D: 110%) and total duration (P<0.05) of PS (L: 70%, D: 150%). In return, ZP (10 mg/kg) presented no effect during L but increased total (40%) and mean duration (37%) of SWS during the D period. DZ modified mean duration of SWS (L: -27%, D: +26%) and increased total duration of SWS (+47%). ZP and DZ induced a more pronounced decrease in Tb than MLT but only DZ induced tachycardia and hypertension.


CONCLUSIONS
We showed that MLT could not promote sleep and its cardiovascular adaptations despite hypothermia, but modulated the period of ultradian sleep cycles. DZ and ZP promoted sleep and induced hypothermia during the D period. Only DZ disrupted sleep architecture and induced adverse effects on cardiovascular parameters.
Mailliet
F
F
UMR INRA-CNRS-Université de Tours 6073, Physiologie de la Reproduction et des Comportements, 37380 Nouzilly, France. Francois.Mailliet@tours.inra.fr
Galloux
P
P
Poisson
D
D
D000818:Animals; D000975:Antioxidants / Q000494:pharmacology*; D001794:Blood Pressure / Q000187:drug effects* / Q000502:physiology; D001831:Body Temperature / Q000187:drug effects* / Q000502:physiology; D003975:Diazepam / Q000494:pharmacology; D006339:Heart Rate / Q000187:drug effects* / Q000502:physiology; D006993:Hypnotics and Sedatives / Q000494:pharmacology*; D008297:Male; D008550:Melatonin / Q000494:pharmacology*; D011725:Pyridines / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D012894:Sleep Stages / Q000187:drug effects* / Q000502:physiology; D013686:Telemetry / Q000379:methods; D000077334:Zolpidem
D000975:Antioxidants; D006993:Hypnotics and Sedatives; D011725:Pyridines; D000077334:Zolpidem; D008550:Melatonin; D003975:Diazepam