Effect of intraventricular administration of calcium and calmodulin antagonist on the blood pressure in the rat.

The effect of intraventricular administration of calcium on the mean arterial pressure in the conscious rat was investigated. Biphasic changes of blood pressure, fugitive rapid increment during the first 3 min and gradual lengthy decrement during the next 60 min were observed by the administration of CaCl2 (30 mumol/kg). Both these changes were significant as compared with the control level. On the other hand, the biphasic response of blood pressure by CaCl2 was abolished by the administration of calmodulin antagonist, W-7, or catecholamine synthesizing enzyme inhibitor, alpha-methyltyrosine. These results are discussed on the basis of our calcium-calmodulin-dependent biogenic amine-synthesizing mechanism.