Effects of verapamil and diltiazem on dopamine release in the central nervous system of spontaneously hypertensive rats.

1. The purpose of the present study was to investigate the effects of Ca(2+)-antagonists (verapamil and diltiazem) on dopamine release in the central nervous system in hypertension. 2. Striatal slices obtained from spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats were prelabelled with [3H]-dopamine, and superfused with Krebs-Ringer solution in vitro. The slices were stimulated electrically at a frequency of 1 Hz. 3. Stimulation-evoked release of [3H]-dopamine from striatal slices was significantly decreased in SHR compared with WKY rats. 4. Exposure of slices to verapamil and diltiazem significantly increased the stimulation-evoked [3H]-dopamine release. The facilitatory effects of the Ca(2+)-antagonists on dopamine release were significantly greater in SHR than in WKY rats. 5. Because central nervous system dopaminergic mechanisms appear to be depressor, the results suggest that the pronounced effects of verapamil and diltiazem on dopamine release in SHR might be involved in the central hypotensive mechanisms of the Ca(2+)-antagonists.