α-Adrenoceptor antagonistic and hypotensive properties of novel arylpiperazine derivatives of pyrrolidin-2-one.

This study focused on a series of pyrrolidin-2-one derivatives connected via two or four methylene units to arylpiperazine fragment. The compounds obtained for α₁- and α₂-adrenoceptors were assessed. The compound with highest affinity for the α₁-adrenoceptors was 1-{4-[4-(2-chloro-phenyl)-piperazin-1-yl]-butyl}-pyrrolidin-2-one (10 h) with pKi=7.30. Compound with pKi (α₁) ⩾6.44 were evaluated in functional bioassays for intrinsic activity at α₁A- and α₁B-adrenoceptors. All compounds tested were antagonists of the α₁B-adrenoceptors. Additionally, compounds 10e and 10h were α₁A-adrenoceptors antagonist. The dual α₁A-/α₁B-adrenoceptors antagonists, compounds 10e and 10h were also tested in vivo for their hypotensive activity in rats. These compounds, when dosed of 1.0 mg/kg iv in normotensive, anesthetized rats, significantly decreased systolic and diastolic pressure and their hypotensive effects lasted for longer than one hour.