Insulin-induced hypoglycemia activates a chemokinergic neuronal pathway in the hypothalamo-pituitary system

Recently, we found the presence of cytokine-induced neutrophil chemoattractant (CINC) neuronal pathway in the hypothalamo-pituitary system. This observation prompted us to investigate the effect of insulin-induced hypoglycemia on CINC neuronal pathway in the hypothalamo-pituitary system. An insulin injection decreased the plasma glucose level, which followed a prompt rise in plasma ACTH level and an increase in serum CINC level. Before the insulin injection, the signal for CINCmRNA was undetectable in the paraventricular hypothalamic nucleus (PVN). The hypoglycemic challenge induced strong hybridization signals of CINC mRNA in the parvocellular and magnocellular subdivision of the PVN within 30 min, and reached the peak within 3 h. No change was observed in the supraoptic nucleus after the hypoglycemic challenge. These studies demonstrate the presence of a hypoglycemia-sensitive chemokinergic neuronal pathway in the hypothalamo-neurohypophysial system and this newly described pathway will provide novel information for understanding pathophysiology of hypoglycemia.