Background Calcium plays a key role in vascular contraction and regulates receptor sensitivity to certain neurotransmitters. Calcium channel blockers are useful in the treatment of both clinical and experimental hypertension. The present study was designed to examine whether there is an alteration of the activity of calcium channels in association with the development of hypertension.Methods Deoxycorticosterone acetate DOCA -salt hypertension was made by subcutaneous implantation of DOCA 200mg/kg strip plus saline drinking 1 and 2-kidney, 1 clip 2K1C hypertension by clipping the left renal artery with a silver clip internal gap of 0.2mm . They were used 4 weeks later. Age-matched normal rats served as a control. Mean arterial pressure MAP and heart rate HR were continuously recorded from the right femoral artery. The drugs were administered intravenously.Results Vehicle alone was without effect on MAP or HR. In normotensive rats, nifedipine infusion 5 and 10 g/kg/min caused a dose-dependent decrease in MAP without significant changes in HR, while Bay k 8644 Bay K, 5 and 10 g/kg/min increased MAP transiently. Both the depressor response to nifedipine and the pressor response to Bay k were more marked in DOCA-salt hypertensive rats than in normotensive rats. The maximal changes in MAP induced by nifedipine 5 and 50 g/kg or Bay K 5 and 50 g/kg were also enhanced in 2K1C hypertensive rats as compared with control rats.Conclusion These results indicate that calcium channel inhibitors and activators can affect on

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