Release of 3H-noradrenaline from the rat vas deferens under various in vitro conditions

The release of ³H-(-)-noradrenaline (NA) from rat vas deferens in vitro was examined under various experimental conditions. It was found that in normal and reserpinized vas deferens the release of NA evoked by (+)-amphetamine (5 times 10^?6 M) or low external Na⁺ (26 mM) was antagonized by imipramine methiodide and desipramine, inhibitors of the NA uptake, but was not dependent on the presence of Ca²⁺ in the medium and was not antagonized by the potent local anaesthetic agent bethoxycaine. The release evoked by veratridine in reserpinized tissue was antagonized by the uptake inhibitors but was in normal tissue only partially inhibited in presence of Ca²⁺ but almost completely in absence of Ca²⁺. The release by high K⁺ (117 mM) + low Na⁺ (26 mM) in normal tissue was dependent on the presence of Ca²⁺ and was antagonized by the muscarinic agonists carbacholine and metacholine and by high concentrations of desipramine. In the reserpinized vasa the corresponding release was not dependent on Ca²⁺ and was not antagonized by the muscarinic agents but was inhibited by high concentrations of desipramine.