Changes in pattern and amount of food intake, induced in rabbits by bilateral cervical sympathectomy and subsequent blinding

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Abstract
Ten adult rabbits were fed ad libitum during more than 18 months, in which a continuous recording was made of the number of food approaches per 30 min. They were initially intact and exposed to an LD 12:12 h‐regime, thereupon deprived of their cervical sympathetic nerves but still exposed to LD 12:12 and, finally, blinded also and kept further on in constant illumination. In all three conditions the food intake pattern is controlled by the action and interaction of two loosely coupled circadian oscillators which in LD are differentially entrained to the two transients and after blinding free‐run with different periods. For one oscillator this period is remarkably constant and deviates less than 1 min from 24 h. Bilateral sympathectomy causes a reduction of food intake which is virtually confined to the illumination periods and, thus, results in an alteration of the LD‐entrained food intake pattern. Since this change can not be explained from a weakened entrainment of the two oscillators to the two transients of the LD schedule, it is suggested to be due to the elimination of a direct influence from the cervical sympathetics on the hypothalamic circadian system.