Decreased food intake of rats kept under adiurnal feeding cycles: effect of suprachiasmatic lesions.

The circadian feeding rhythm and food intake under restricted feeding conditions, including adiurnal feeding cycles, were examined in rats with bilateral lesions of the suprachiasmatic nucleus (SCN). Although rats with SCN-lesions ate nearly as much food per day as those with control-lesions, their feeding pattern did not show circadian rhythmicity. When rats with control-lesions were fed for 5 hr once every 20 hr or for 7 hr once every 28 hr, they ate less than when they were fed for 6 hr once every 24 hr, probably due to some effect of desynchronization between the feeding cycle and an endogenous circadian oscillator. Decreased food intake under adiurnal feeding cycles was also observed in rats with SCN-lesions as in those with control-lesions. It is suggested that the circadian rhythm entrained by food is related to an endogenous time-keeping system that does not include the SCN.