PMID: 6148393Aug 1, 1984Paper

Antagonism of the antidiarrhoeal effect of clonidine and the lethal effect of noradrenaline in rats: a reliable procedure to evaluate the in-vivo alpha 1- and alpha 2-blocking activity of drugs?

The Journal of Pharmacy and Pharmacology


Eight compounds with alpha-adrenergic blocking activity were tested for their ability to antagonize the antidiarrhoeal effect of clonidine (clonidine test) and the lethal effect of noradrenaline (noradrenaline test). Six of the compounds studied are alpha-adrenergic blocking agents with known alpha 2/alpha 1 selectivity. Two compounds, ketanserin (R 41 468) and butanserin (R 53 393), are 5-hydroxytryptamine S2-antagonists. The ED50-values (mg kg-1) obtained in the clonidine test were: phentolamine (0.34), RX781094 (0.34), yohimbine (0.51), piperoxan (9.36), butanserin (greater than 5.0), prazosin (greater than 10.0), phenoxybenzamine (greater than 40.0), and ketanserin (greater than 80.0). In the noradrenaline test the ED50's (mg kg-1) were: butanserin (0.014), prazosin (0.032), phentolamine (0.59), phenoxybenzamine (1.02), ketanserin (4.69), RX781094 (12.4), piperoxan (21.5), and yohimbine (25.0). The selectivity alpha 2/alpha 1-ratios (ED50 clonidine/ED50 noradrenaline were: yohimbine (0.020), RX781094 (0.027), piperoxan (0.44), phentolamine (0.58), ketanserin (greater than 39), prazosin (greater than 312), and butanserin (greater than 357). These results show that yohimbine and RX781094 are equipotent and relatively selectiv...Continue Reading


May 1, 1977·British Journal of Pharmacology·J C DoxeyJ M Walker
Aug 1, 1978·The Journal of Pharmacy and Pharmacology·K F Rhodes, J F Waterfall
Apr 15, 1979·Biochemical Pharmacology·C L WoodR J Lefkowitz
Jun 1, 1981·The Journal of Pharmacy and Pharmacology·T NakakiR Kato
Jan 1, 1981·Medicinal Research Reviews·S Fielding, H Lal
Apr 1, 1980·Pharmacology, Biochemistry, and Behavior·G T ShearmanR C Ursillo
Jan 1, 1981·Journal of Clinical Pharmacology·H LalR C Ursillo

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