Melatonin and zopiclone: the relationship between sleep propensity and body temperature.
OBJECTIVE
The sleep promoting effects of the sedative-hypnotics, melatonin and temazepam, have been associated with a decline in core body temperature (Tc). To determine whether changes in body temperature are a general feature of sedative-hypnotics, the present study compared the sleep inducing, core and peripheral temperature effects of melatonin, with those of zopiclone.


METHODS
Subjects were supine from 08:00-21:30 h and received melatonin, zopiclone or placebo at 14:00 h.


METHODS
Individual, light and temperature controlled bedrooms.


METHODS
12 healthy, young, adults (7m, 5f; 20.3 +/- 0.6 years).


METHODS
Melatonin (5mg), zopiclone (Imovane; 7.5 mg) and placebo were administered in a double-blind, crossover design.


RESULTS
From 11:00-20:00 h, modified hourly multiple sleep onset latency tests (MSLT) of a 20-min duration were conducted and heart rate (HR) was recorded. Tc and foot temperature (T(Ft)) were recorded continuously using thermistors. Compared with placebo, melatonin and zopiclone significantly reduced sleep onset latency (SOL) to stage 1 (by 3.50 +/- 0.73 min and 6.80 +/- 0.61 min, respectively) and reduced Tc (by 0.22 +/- 0.02C and 0.14 +/- 0.02C, respectively). For melatonin, Tc declined as the result of an increase in peripheral heat loss (increase in T(Ft) of 1.65 +/- 0.43 degrees C), and possibly a reduction in heat production as indicated by a decrease in HR (4.56 +/- 0.94 bpm). Zopiclone increased heat loss (increase in T(Ft) of 1.43 +/- 0.68C) and had no cardiac effects. For melatonin, a negative association was found between Tc (mean r=-0.43), however, this association was only weak for zopiclone (mean r=-0.23).


CONCLUSIONS
These results suggest that body temperature changes may be a general feature of sedative-hypnotics. The potential role of this effect in the promotion of sleep appears to vary between agents.
Holmes
Alexandra L
AL
Centre for Sleep Research, University of South Australia, Woodville. alex.holmes@unisa.edu.au
Gilbert
Saul S
SS
Dawson
Drew
D
D000328:Adult; D000975:Antioxidants / Q000494:pharmacology*; D053961:Azabicyclo Compounds; D001831:Body Temperature / Q000187:drug effects*; D001833:Body Temperature Regulation / Q000187:drug effects; D018592:Cross-Over Studies; D004311:Double-Blind Method; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D006993:Hypnotics and Sedatives / Q000494:pharmacology*; D008297:Male; D008550:Melatonin / Q000494:pharmacology*; D010879:Piperazines / Q000494:pharmacology*; D012890:Sleep / Q000187:drug effects*; D013997:Time Factors
D000975:Antioxidants; D053961:Azabicyclo Compounds; D006993:Hypnotics and Sedatives; D010879:Piperazines; C515050:zopiclone; D008550:Melatonin