Fall in blood glucose level precedes meal onset in free-feeding rats.

It has been suggested for a long time that the metabolic stimulation to eat or the hunger arousal of eating, originated from a fall in the blood glucose level induced by the periodic failure of hepatic glucose production to match the peripheral glucose uptake. However, this suggestion has not been substantiated directly by the results of periodic blood glucose evaluations performed during intermeal intervals in free-fed rats. In this experiment, a technique involving a continuous blood glucose determination over several hours was used in free-feeding, undisturbed rats. It was shown that all nocturnal and diurnal meals were preceded by a 6 to 8% fall of blood level, starting 5 to 6 min prior to meal onset. The overall consequences of these findings are discussed.