UNLABELLED: A combination of biochemical, physiological and electropharmacological methods was employed to examine the occurrence of neuropeptide Y and the pre- and postjunctional effects of this peptide on sympathetic neuromuscular transmission in the mouse vas deferens. This tissue had a high content of neuropeptide Y-like immunoreactive material, suggesting a dense innervation by neuropeptide Y-containing nerve fibres. Addition of neuropeptide Y at concentrations from 5 X 10(-9) to 5 X 10(-7) M induced both pre- and postjunctional effects in vitro. Neuropeptide Y per se induced a rise in the resting tension, and "instantly" potentiated the contractile effects of exogenous noradrenaline and of the stable adenosine 5'-triphosphate (ATP) analogue, alpha,beta-methylene ATP. Neuropeptide Y reduced the secretion of [3H]noradrenaline evoked by electrical nerve stimulation, and selectively depressed the stimulus-evoked, but not the spontaneously occurring excitatory junction potentials in smooth muscle cells. Further, neuropeptide Y reduced the amplitudes of the twitch contractions evoked by electrical field stimulation with short stimulus trains at 10 Hz, and also (although to a smaller extent) the delayed contractile response to longer trains of nerve stimuli. The pre- and postjunctional effects of neuropeptide Y were not changed by alpha- or beta-adrenoceptor blocking agents, or by tachyphylaxis to the effects of ATP, or by the calcium channel blocker nifedipine. IN CONCLUSION: sympathetic neuromuscular transmission in the mouse vas deferens may be mediated not only by noradrenaline and ATP, but also by neuropeptide Y.(ABSTRACT TRUNCATED AT 250 WORDS)
UNLABELLED: A combination of biochemical, physiological and electropharmacological methods was employed to examine the occurrence of neuropeptide Y and the pre- and postjunctional effects of this peptide on sympathetic neuromuscular transmission in the mouse vas deferens. This tissue had a high content of neuropeptide Y-like immunoreactive material, suggesting a dense innervation by neuropeptide Y-containing nerve fibres. Addition of neuropeptide Y at concentrations from 5 X 10(-9) to 5 X 10(-7) M induced both pre- and postjunctional effects in vitro. Neuropeptide Y per se induced a rise in the resting tension, and "instantly" potentiated the contractile effects of exogenous noradrenaline and of the stable adenosine 5'-triphosphate (ATP) analogue, alpha,beta-methylene ATP. Neuropeptide Y reduced the secretion of [3H]noradrenaline evoked by electrical nerve stimulation, and selectively depressed the stimulus-evoked, but not the spontaneously occurring excitatory junction potentials in smooth muscle cells. Further, neuropeptide Y reduced the amplitudes of the twitch contractions evoked by electrical field stimulation with short stimulus trains at 10 Hz, and also (although to a smaller extent) the delayed contractile response to longer trains of nerve stimuli. The pre- and postjunctional effects of neuropeptide Y were not changed by alpha- or beta-adrenoceptor blocking agents, or by tachyphylaxis to the effects of ATP, or by the calcium channel blocker nifedipine. IN CONCLUSION: sympathetic neuromuscular transmission in the mouse vas deferens may be mediated not only by noradrenaline and ATP, but also by neuropeptide Y.(ABSTRACT TRUNCATED AT 250 WORDS)