The effect of prazosin on the guinea-pig ileum

British Journal of Pharmacology
S O Fagbemi, L A Salako

Abstract

1 The alpha-adrenoceptor blocking activity of prazosin was compared with that of phentolamine, yohimbine and phenoxybenzamine in the guinea-pig isolated ileum. 2 Phentolamine (2.56 X 10(-8) to 2.56 X 10(-6) M) and yohimbine (5.12 X 10(-8) to 5.12 X 10(-6) M) antagonized the sympathetic inhibition of twitches induced by transmural stimulation, whereas prazosin (5.28 X 10(-8) to 5.28 X 10(-6) M) and phenoxybenzamine (4.2 X 10(-9) to 4.2 X 10(-7) M) had no effect. 3 Phentolamine, yohimbine, prazosin and phenoxybenzamine antagonized the relaxant response of the ileum to periarterial nerve stimulation and to exogenous noradrenaline in the absence of transmural stimulation. 4 The pA2 value for phentolamine against noradrenaline in the transmurally-stimulated gut (presynaptic alpha-adrenoceptor site; 8.17 +/- 0.04) was significantly different from that in the non-stimulated gut (postsynaptic alpha-adrenoceptor site; 6.88 +/- 0.12). 5 Phentolamine and prazosin probably block noradrenaline responses at the same alpha-adrenoceptor site on the postsynaptic membrane.

References

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Citations

Apr 1, 1983·Naunyn-Schmiedeberg's Archives of Pharmacology·R A LefebvreM G Bogaert
May 1, 1984·Naunyn-Schmiedeberg's Archives of Pharmacology·R A LefebvreM G Bogaert
Feb 1, 1984·British Journal of Pharmacology·J FontaineJ Reuse
Apr 17, 2004·Neurogastroenterology and Motility : the Official Journal of the European Gastrointestinal Motility Society·S FruhwaldP Holzer
Aug 1, 1996·Journal of Autonomic Pharmacology·A MacDonaldP J Scott

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