THE EFFECTS OF ETHANOL ON THE CIRCADIAN-RHYTHMS OF LOCOMOTOR-ACTIVITY AND BODY-TEMPERATURE IN RATS

The present study was undertaken to examine the effects of ethanol on the circadian rhythms of locomotor activity and body temperature in blinded rats. Locomotor activity was measured by running wheel activity cages at 5 min intervals by a digital computer system. Body temperature was automatically recorded at 30 min intervals by a thermistor implanted in the dorsal area of the rat. After the stable free-running rhythms were obtained, the animals were exposed to acute intraperitoneal treatment with ethanol (3g/kg, 20% w/v dissolved in saline) at eight circadian time (CT) points (CT2, CT6, CT9, CT11, CT15, CT18, CT21, CT23). Phase advances were observed at between CT9 and CT15 with the maximum at CT11 in locomotor activity and body temperature circadian rhythms, Phase delay were found at between CT21 and CT2 with the maxmum phase delap at CT21 in both two circadian rhythms. The magnitude of the phase-shifts was much larger in the body temperature rhythm than in the locomotor activity rhythm. The phase response curves (PRCs) of ethanol are similar to those of dark pulses since both PRCs: have a phase delay region in the late subjective night and the phase advance region in the late subjective day. Free-running periods prolonged significantly after treatment with ethanol at CT11, CT15 and CT21 in both two circadian rhythms. These results suggest that ethanol produces phase-shifts in the circadian rhythms of locomotor activity, and body temperature, of which the magnitude and direction are dependent upon CT when the ethanol is given. and, moreover, that ethanol-induced changes in the free-running periods in both locomotor activity and body temperature circadian rhythms are dependent upon the respective PRCs.