Cell experiment:

Arteries and portal veins isolated male Wistar rats (150 to 300 g) are sued and prepared for in vitro studies. Vessels are incubated with appropriate concentrations of Tiodazosin, prazosin or phentolamine for one hour. Contractile responses to norepinephrine or potassium chloride are then repeated in the presence of Tiodazosin[1].

Tiodazosin is a potent competitive postsynaptic alpha adrenergic receptor antagonist.

Tiodazosin is a potent competitive postsynaptic alpha adrenergic receptor antagonist. In the mesenteric artery, Tiodazosin produces a parallel shift to the right in the concentration response curves to norepinephrine. A Schild plot constructed from two concentrations of Tiodazosin results in a pA2 value of 8.66 and a slope equal to -0.99. Tiodazosin inhibits contraction to norepinephrine in the portal vein and the inhibition results in a nonparallel inhibition of the norepinephrine concentration-response curve with a marked depression of maximal norepinephrine response[1].

[1]. Cohen ML, et al. In vitro comparison of the pre- and postsynaptic alpha adrenergic receptor blocking properties of prazosin and tiodazosin (BL5111).