A study of the post-tetanic twitch depression at the prostatic end of the rat vas deferens.
The effects of different drugs on the post-tetanic twitch responses of the prostatic end of the isolation rat vas deferens were examined. Following repetitive field stimulation (4-5 Hz for 40-60 s), the post-tetanic twitches (0.2-0.5 Hz) were depressed relative to the steady-state pretetanic twitches. Maximum post-tetanic twitch depression (PTD) occurred 15-30 s after the tetanic stimulation. The PTD was not reversed but deepened and prolonged by the presynaptic alpha 2-adrenoceptor antagonists idazoxan (RX781094) or yohimbine (10(-7) M) alone or combined with the neuronal uptake blocker, desipramine (10(-6) M). The PTD was insensitive to the beta-adrenoceptor blocker, propranolol (10(-6) M), the P1-purinoceptor antagonist, 8-phenyltheophylline (10(-5) M) or the prostaglandin E synthesis inhibitor, indomethacin (10(-6) M). Pre- and post-tetanic contractions to superfused noradrenaline (NA), adenosine 5'-triphosphate (ATP), or beta, gamma-methylene ATP (beta, gamma-mATP) (bolus injections into superfusate, 1-8 X 10(-5) M) were not significantly (p less than 0.01) different. The PTD was absent in high magnesium (6.2-11.2 mM) solutions. These results are consistent with the PTD having an intrinsic presynaptic origin. They are discussed in relation to stimulation-induced modulation of transmitter release.
D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000818:Animals; D004558:Electric Stimulation; D004594:Electrophysiology; D007213:Indomethacin / Q000494:pharmacology; D008274:Magnesium / Q000494:pharmacology; D008297:Male; D011467:Prostate / Q000502:physiology*; D051381:Rats; D013806:Theophylline / Q000031:analogs & derivatives / Q000494:pharmacology; D014649:Vas Deferens / Q000502:physiology*
D000317:Adrenergic alpha-Antagonists; D000319:Adrenergic beta-Antagonists; D013806:Theophylline; C028322:8-phenyltheophylline; D008274:Magnesium; D007213:Indomethacin