RESUMO
1. In rat vas deferens, electrical field stimulation (EFS) evoked a muscular biphasic tetrodotoxin (TTX)-sensitive contractile response. 2. The amplitude of this response increased with the frequency of stimulation. 3. After each stimulation, nitric oxide (NO) release was assayed and found to be released in a frequency-dependent manner. 4. NO release also occurred after treatment with exogenous neurotransmitters, adenosine 5'-triphosphate (ATP) and noradrenaline (NA). 5. Prazosin and pyridoxalphosphate-6-azophenyl-2',4'-disulphonic acid (PPADS), respective antagonists of alpha1-adrenoceptors and P2x purinoceptors, inhibited NO release induced by NA and ATP. Both prazosin and PPADS inhibited NO release by EFS. 6. TTX failed to modify the NO release induced by exogenous neurotransmitters but abolished the release of NO and contractile response by EFS. 7. EFS and released noradrenaline and ATP induce the release of NO through postjunctional alpha1 -adrenoceptors and P2x-purinoceptors, respectively.