In this experiment, newly synthesized ultrashort-acting blockers of β-adrenergic receptors were tested. Compounds were synthesized at the Department of Chemical Drugs of Pharmaceutical Faculty VFU Brno as esters of aryloxyaminopropanol, thereby gaining a very short half-life in blood plasma. Experiment was conducted in vivo in a rat model. Changes in systolic blood pressure and heart rate were monitored by invasive method in normotensive rats. The values of blood pressure and heart rate were recorded for 20 minutes following the i.v. administration of tested substances or placebo into the jugular vein. In the experiment was tested a series of four substances (2MC2, 2MC2b, 2MC2c, 2MC2d) with different alkyl chain length at a dose of 3.0 mg·kg⁻¹. After evaluation of results was carried out the second part of the experiment, i.e. testing of substances 2MC2c and 2MC2d at a lower dose of 1.0 mg·kg⁻¹. The results show the best effect of 2MC2d, asubstance with longest alkyl chain and highest lipophilicity.