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Parathyroid hormone-related protein (PTHrP) is one of the main factors from tumors causing malignancy associated hypercalcemia. It is also expressed in various kinds of normal tissues including vascular smooth muscle systems. Colocalization of the PTH/PTHrP receptor and locally produced PTHrP and its vasorelaxant activities suggest that PTHrP has a regulatory role in the modulation of blood pressure (BP). There have been many evidences that indicate the importance of circulating PTH and PTH/PTHrP receptors in the regulation of BP in various conditions. These data suggest that, under normal physiological conditions, locally produced PTHrP is a real factor that regulates these smooth musele systems in a paracrine or autocrine fashion. The central nervous system also has a very important role to regulate the BP. The evidence that PTHrP is expressed in the central nervous system and the presence of the PTHrP immunoreactivity in human cerebrospinal fluid lead to the possibility that PTHrP has some role in the central regulation of BP. We have found that intraventricularly administered PTHrP had a pressor effect on systemic BP which support the previous possibility.