Additional evidence that the suprachiasmatic nucleus is the center for regulation of insulin secretion and glucose homeostasis.

The role of the suprachiasmatic nucleus (SCN) in photoperiod-dependent hyperglycemia due to D-mannitol (MA) and D-glucose (GL) was investigated using SCN-lesioned rats. In control rats, intracranial injection of MA and GL caused hyperglycemia only in the light period and dark period, respectively. In SCN-lesioned rats, administration of MA and GL caused no change in plasma glucose level, irrespective of the lighting condition. SCN-lesioned rats have higher plasma insulin levels than sham-operated rats through this experiment. From these findings, we propose that the SCN is involved in a glucose homeostasis and regulation of insulin secretion.