Effect of cadmium or magnesium on calcium-dependent central function that reduces blood pressure

The effect of intracerebroventricular (i.c.v.) administration of cadmium or magnesium on central calcium-dependent blood pressure regulation was inves tigated ii. The systolic blood pressure of spontaneously hypertensive rats (SHR; male, 13 weeks of age) decreased following i.c.v, administration of c admium chloride (20 nmol/rat), and increased following i.c.v. administratio n of magnesium chloride (20, 600, and 1200 nmol/rat). The hypotensive effec t of cadmium was suppressed by i.c.v. administration of W-7 (a calmodulin a ntagonist, 30 mu g/rat). Taking into consideration these results with our p revious reports, it is suggested that cadmium binds to the calcium-binding sites of calmodulin and activates calcium/calmodulin-dependent enzymes in a disorderly manner, whereas magnesium does not. Therefore, cadmium increase s dopamine synthesis in the brain via a calmodulin-dependent system, and th e resultant increase in dopamine levels inhibits sympathetic nerve activity and reduces blood pressure in SHR.