a,1-- Adrenergic and 5--HT2--Serotonergic Effects of Some f3--Alkoxy--f3--phenylethylamines on Isolated Rat Thoracic Aorta

1. Ten racemic ~-alkoxy-~-phenylethylamines were found to elicit concentrationdependent contraction of the isolated rat thoracic aorta with apparent pD2 values in the 4.56-6.76 range. With one exception, which produces the same maximal contraction (Emax) as serotonin (5-HT), the Emax values attained with these compounds are lower than those produced by either 5-HT or norepinephrine (NE). 2. Pretreatment with either prazosin or ketanserin (10-s M) leads in most cases to decreased Emax values and slopes in the dose-response curves. Apparent serotonergic (pD2S) and adrenergic (pD/) pD2 values going from 4.22 to 6.08 (pD2S) and from 3.87 to 5.27 (pD2A) were calculated from results obtained in the presence of prazosin or ketanserin, respectively. 3. In the 10-7-10-5 M range, and in contrast with the results obtained with the previous compounds, BON [(±)-2-(2,5-dimethoxy-4-nitrophenyl)-2-methoxy-ethylaminel behaves as an antagonist to both 5-HT and NE (apparent pA2=7.08 and 7.45, respectively) in this preparation.This work was supported in part by CAPES (Brazil) through a grant to M. A. T