INHIBITORY ACTION OF NEUROPEPTIDE Y (NPY) ON ELECTRICALLY EVOKED TWITCHES OF RAT VAS DEFERENS ; EFFECT OF FREQUENCY OF STIMULATION

摘要

The inhibitory effect of NPY (30 nM) on twitches of isolated rat vas deferens evoked by electrical field stimulation (0.008, 0.016, 0.16, 0.25 and 0.5 Hz) has been studied, in the absence/presence of phentolamine 5μM and propranolol 5μM. RESULTS: In the absence of NPY the amplitude of twitch declined with increasing frequency of stimulation, being greatest at 0.008 Hz and least at 0.5 Hz. With NPY the rate of onset of inhibition was frequency related, being quickest at the highest frequency (0.5 Hz) and slowest at the lowest frequency uses (0.008 Hz). The degree of maximum inhibition increased with increasing frequency of stimulation up to 0.16 Hz but declined with further increases in the frequency of stimulation. Results were not affected by the presence or absence of phentolamine and propranolol. CONCLUSION: It is concluded that the inhibitory effect of NPY on twitches is affected by the frequency of twitches, through a mechanism which possible involves endogenous NPY but not endogenous noradrenaline.