The present paper links up with the study of principal pharmacological effects of newly synthesized aryloxyaminopropanols substituted with 1,4-piperazine derivatives in the hydrophilic moiety of the molecule. The substance with the working name IIIv showing the highest b-adrenolytical and vasodilating effect underwent further pharmacological evaluations with the aim of contributing to the elucidation of the mechanism of its action. After 7-day administration of the substance in two doses (5 and 50 mg.kg -1 ), the changes in the reactibility of arterial preparations were investigated on three models of the contraction of the isolated rat aorta (KCl, noradrenaline, and PGF2a) from both qualitative and quantitative views. The results were also supplemented with organometric studies of the effect of the substance in rats.

        Key words: aryloxyaminopropanols – b-adrenolytic – vasodilating – isolated aorta