The use of ryanodine and calcium channel blockers to characterize intra- and extracellular calcium pools mobilized by noradrenaline in the rat vas deferens.

Ryanodine (0.03-10 microM) abolished the phasic component of the contractile response to noradrenaline in the rat vas deferens but had less effect on the tonic component of this response. In contrast, nifedipine and methoxyverapamil (D600, 0.3-0.8 microM) blocked only the tonic component of the noradrenaline, adrenaline or phenylephrine-induced contractions. These results suggest that the phasic component of the noradrenaline-induced response is related to the release of intracellular calcium whereas the tonic phase of the contraction involves calcium influx via membrane channels sensitive to dihydropyridine and diphenylalkylamine calcium channels blockers.