RS 17053 hydrochloride is a potent and selective α1_A adrenoceptor antagonist, with a pK_i value of 9.1 in native cell membrane and a pA₂ value of 9.8 in functional assays. IC50 & Target: pKi: 9.1 (α1_A adrenoceptor in native cell membrane)
pA2: 9.8 (α1_A adrenoceptor)^[1]. In Vitro: In several tissues from rat and cloned adrenoceptors, RS 17053 hydrochloride displays high affinity for the α1A-adrenoceptor (pK_i and pA₂ estimates of 9.1-9.9) and a 30-100-fold selectivity over the α1 B and the α1 D-adrenoceptor subtypes (pK_i and pA₂ estimates of 7.7-7.8). However, in isolated smooth muscle preparations from human LUT tissues, RS 17053 hydrochloride antagonizes responses to NE only at high concentrations. Estimates of affinity (pA₂) at α1-adrenoceptors mediating NE-induced contractions are 7.5 in prostatic periurethral longitudinal smooth muscle (compared with 8.6 for prazosin), 6.9 in anterior fibromuscular stroma (prazosin, 8.9), and 7.1 in bladder neck (prazosin, 8.5)^[1]. In Vivo: RS 17053 hydrochloride has a rapid onset of action, and a duration of action exceeding 60 min. RS 17053 hydrochloride pretreatment significantly alteres food intake [F(4, 132) 5 6.28, p , 0.0001]. 10 mg/kg RS-17053 significantly suppresses food intake^[2].