Effects of several calcium channels modulators on the [3H]noradrenaline release and 45Ca influx in the rat vas...

1. The effects of nifedipine (1 microM), CdCl2 (0.1 mM) and the Bay K 8644 enantiomers (1 microM) on [3H]noradrenaline release and 45Ca uptake in epididymal and prostatic rat vas deferens were investigated. 2. Nifedipine, CdCl2 and Bay K 8644 optical isomers did not affect the basal tritium release. However, the [3H]noradrenaline release evoked by high potassium (50 mM) from both portions of rat vas deferens was markedly inhibited by CdCl2, scarcely affected by nifedipine and not modified by Bay K 8644 enantiomers. 3. (-)-Bay K 8644 increased the basal and potassium (50 mM) induced 45Ca uptake whereas (+)-Bay K 8644, nifedipine and CdCl2 did not alter the basal 45Ca uptake. However, they strongly inhibited the uptake induced by potassium in both portions of rat vas deferens. 4. These results suggest that the calcium channels (mainly L type) are involved on the contractions in rat vas deferens epididymal and prostatic halves; these channels differ from those present in sympathetic nerve terminals (likely of N Type) which modulates the NA release. 5. This study also shows that Bay K 8644 optical isomers possess opposite effects on the L channels of bisected rat vas deferens smooth muscle.