Abstract
1. 1. The effect of neuropeptide Y (NPY) on [ 3H]noradrenaline ([ 3H]NA) release-evoked by 5-Hz electrical stimulation or 5 μm calcium ionophore A 23187 was studied in vitro in guinea-pig vas deferens. 2. 2. The evoked tritium overflow (which reflected [ 3H]NA release) was determined by liquid scintillation spectrometry. 3. 3. NPY, 1 μM, reduced electrically-evoked tritium overflow. NPY reduction was more pronounced upon 20-sec, 3 msec continuous stimulation (73.2 ± 4.4%) and upon 5-min, 1 msec intermittent stimulation (47.8 ± 2.4%) as compared to the reduction upon 5-min, 1 msec continuous stimulation (24.3 ± 3.8%). Forskolin (0.1-1 μM) and theophylline (0.65–1.25 mM)dose-dependently diminished this NPY reducing effect. 4. 4. NPY, 1 μM, reduced A 23187-evoked tritium overflow by 52.3 ± 7.1%. Forskolin (5 μM) and theophylline (1.25 mM) significantly decreased the effect of NPY. 5. 5. It is concluded that in guinea-pig vas deferens NPY reduces [ 3H]NA release through affecting adenylate cyclase and the processes responsible for calcium mobilization.
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