Objective:The aim of this study was to evaluate the influence of 1,25-dihydroxy vitamin D3[1,25(OH)2D3]deficiency on brain vasopressin expression and cerebrovascular function in hypertension. Methods:Mean arterial pressure,brain vasopressin(VP)expression and cerebrovascular reactivity of two-month-old 1-alpha-hydroxylase[1α(OH)ase]gene knockout mice and their wild-type littermates were analyzed and compared using tail-cuff plethysmography,immunohistochemistry and online videomicroscopy. Results:Compared with their wild-type littermates,1α (OH)ase-/- mice showed high mean arterial pressure,increased VP positive neurons in hypothalamus and cerebral arteries featured markedly decreased dilatory responses to acetylcholine (ACh)and a reduced basal production of NO as exemplified by the attenuated diameter decrease during NOS inhibition with L-NNA. Conclusion:l,25(OH)2D3 plays an important role in neuroendocrine regulation and cerebrovascular function in hypertensive progression.