Fadolmidine, also known as MPV-2426, is a novel and potent alpha2 -adrenoceptor (alpha2) -AR) agonist developed for spinal analgesia. Fadolmidine displayed high affinity and full agonist efficacy at all three human alpha2-adrenoceptor subtypes (A, B and C) in transfected CHO cells with EC50 values (nM) of 0.4, 4.9 and 0.5, respectively. Fadolmidine inhibited also electrically evoked contractions in rat vas deferens demonstrating the activation of rodent presynaptic alpha2D-adrenoceptors with an EC50 value of 6.4 nM. Moreover, fadolmidine was a full agonist at human alpha1A-adrenoreceptor (EC50 value 22 nM) and alpha1B-adrenoreceptor (EC50 value 3.4 nM) in human LNCaP cells and transfected HEK cells, respectively. Agonism at the alpha1-adrenoceptor was also observed in rat vas deferens preparations although at lower potency (EC50 value 5.6 microM). Fadolmidine demonstrated potent alpha2-adrenoceptor agonist activity also in vivo by inhibiting electrically induced tachycardia i......