Release of 5‐hydroxytryptamine, dopamine and noradrenaline in the rat vas deferens in the presence of compound 48/80, veratridine or K+

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Abstract
1 The release of 5-hydroxytryptamine (5-HT), dopamine and noradrenaline (NA) from the rat isolated vas deferens was estimated by high performance liquid chromatography with electrochemical detection. 2 Compound 48/80, which is known to release 5-HT and histamine from mast cells, induced a concentration-related, rapid overflow of 5-HT from the rat isolated vas deferens, releasing about 50% of the 5-HT present in the tissue at a concentration of 300 μg ml−1. The drug did not induce the release of either dopamine or NA. 3 The depolarizing agents veratridine (10 μm) or K+ (100mm) induced the release of 5–10% of the 5-HT present in the vas deferens, but did not evoke the overflow of 5-HT from isolated mast cells. 4 Veratridine induced the release of a greater proportion of the dopamine than of the NA contained in the vas deferens (41.0 ± 5.5 vs 17.9 ± 2.0%, after 20 min of exposure to the drug, n = 6). In contrast, K+ evoked the release of both amines equally. 5 It is concluded that in the rat vas deferens 5-HT is stored in mast cells and also in cells responsive to depolarizing stimuli. It is suggested that 5-HT could be a neuromodulator or a neurotransmitter in this organ. Veratridine and K+ induce the release of dopamine in addition to NA.