Hypothalamus regulates calcium metabolism in rats.

Hypothalamic mechanisms of blood calcium homeostasis and their functional heterogeneity were investigated in rats. Electrical and chemical stimulation of the lateral hypothalamic area (LHA), the paraventricular nucleus (PVN) and the ventromedial nucleus of the hypothalamus (VMH) induced hypocalcemia. The hypocalcemic effect of PVN stimulation was suppressed by vagotomy of the thyroid/parathyroid branches, while that of LHA and VMH stimulation was eliminated by gastric vagotomy. Immobilization (IMB) stress elicited hypocalcemia through VMH-gastric vagal activation. Both IMB- and LHA stimulation-induced hypocalcemia was antagonized by muscarinic antagonist and histamine H2 blocker. The former was also blocked by alpha-blocker and gastrin release inhibitor, while the latter was antagonized by an beta-blocker. The results suggest that hypothalamic nuclei are involved in regulation of blood calcium homeostasis via the gastric or thyroid/parathyroid vagus. Muscarinic, histamine H2, adrenergic and gastrin receptors mediate the hypocalcemic effect of the hypothalamo-vagal activation depending on behavioral conditions and receptor subtypes.