PT - JOURNAL ARTICLE AU - Simone Tambaro AU - Stefania Ruiu AU - Christian Dessi AU - Raymond Mongeau AU - Giorgio Marchese AU - Luca Pani TI - Evaluation of Tamsulosin and Alfuzosin Activity in the Rat Vas Deferens: Relevance to Ejaculation Delays AID - 10.1124/jpet.104.074740 DP - 2005 Feb 01 TA - Journal of Pharmacology and Experimental Therapeutics PG - 710--717 VI - 312 IP - 2 4099 - http://jpet.aspetjournals.org/content/312/2/710.short 4100 - http://jpet.aspetjournals.org/content/312/2/710.full SO - J Pharmacol Exp Ther2005 Feb 01; 312 AB - The effect of two α-adrenergic receptor antagonists widely employed in the therapy of benign prostatic hyperplasia, tamsulosin [(-)-(R)-5-[2-[[2-(0-ethoxyphenoxy) ethyl]amino]propyl]-2-methoxybenzenesulfonamide] and alfuzosin [(±)-N-[3-[(4-amino-6,7-dimethoxy-2-quinazolinyl) methylamino]propyl] tetrahydro-2-furancarboxamide], was investigated in the rat vas deferens. Because several clinical studies have shown that tamsulosin causes ejaculatory disorders, this study also evaluated the possible mechanisms implicated in these disorders by comparing the effect of tamsulosin with that of alfuzosin. Tamsulosin competitively antagonized the contractions induced by noradrenaline in vitro in the epididymal portion of the vas deferens with a potency pA2 value of 9.2 ± 0.8. In the prostatic portion, tamsulosin increased the amplitude of intermittent spikes induced by exogenous noradrenaline (100–1000 μM). In both portions of the vas deferens, alfuzosin behaved as an α-adrenergic antagonist blocking the contractions induced by exogenous noradrenaline without altering spikes. The administration of tamsulosin (3 μg/kg i.v.) significantly reduced the contractions evoked by electrical pulses in the epididymal portion, whereas it increased those produced in the prostatic portion. Intravenous tamsulosin antagonized the contraction produced by exogenous noradrenaline, whereas alfuzosin administration (10 μg/kg i.v.) did not change the electrically induced contractions in both portions of the rat vas deferens and did not antagonize the contractions produced by exogenous noradrenaline. The fact that tamsulosin unusually enhances noradrenaline-induced intermittent spike contractions and nerve stimulation-induced twitches in the prostatic portions might be linked to its greater propensity to cause sexual dysfunctions.