Aim:To comparatively study the pharmacological profiles of 3-methyl-3-azabicyclo(3,3,1)nonanyl-9-α-yl-α-cyclopentyl-α-phenyl-α-glycolate(phencynonatehydrochloride,CPG),an anticholinergic agent,and its enantiomers[R(-)-andS(+)-CPG].Methods:The affinity and relative efficacy were tested usingradioligand-binding assay with muscarinic acetylcholine receptors from rat cere-bral cortex.The pharmacological activities were assessed in three individual experi-ments:(1)potentiating the effect of subthreshold hypnotic dose of sodiumpentobarbital;(2)inhibiting oxotremorine-induced salivation;and(3)inhibitingthe contractile response to carbachol.Results:The order of potency of phency-nonate hydrochloride and its optical isomers to inhibit the binding of[~3H]quinucli-dinyl benzilate([~3H]QNB)was R(-)-CPG(K_i=46.49±1.27nmol/L)>CPG(K_i=271.37±72.30 nmol/L)>S(+)-CPG(K_i=1263.12±131.64 nmol/L).The results showed thatR(-)-CPG had the highest affinity to central muscarinic receptors among the threecompounds,but did not show any central depressant effects at dose from 10.00 to29.15 mg/kg.CPG increased the effects of subthreshold hypnotic dose of sodiumpentobarbital induced-sleeping[the ED_(50)±95% LC value was 21.06±3.04 mg/kg].CPGand R(-)-CPG displayed nearly equipotent effect in depressing oxotremorine-induced salivation[the ED_(50)±95% LC for R(-)and CPG were 1.10±0.28 and 1.07±0.15 mg/kg,respectively],and the contractile response to carbachol(pA_2 valuesfor R(-)and CPG were 6.84 and 6.80,respectively).S(+)-CPG presented the lówestanticholinergic profiles,but could potentate effects of its enantiomers in somemanner.Conclusions:These data suggested that R(-)-CPG acted as an eutomerin racemate and a competitive antagonist to acetylcholine muscarinic receptors,but S(+)-CPG was less active in comparison to R(-)-CPG and its racemate.Thecentral depressant effects of R(-)-CPG and S(+)-CPG were lower in comparison toits racemate. Aim: To comparatively study the pharmacological profiles of 3-methyl-3-azabicyclo (3,3,1) nonanyl-9-α-yl- α-cyclopentyl-α-phenyl- α -glycolate (phencynonate hydrochloride, CPG), an anticholinergic Agents and The enantiomers were tested using radioligand-binding assay with muscarinic acetylcholine receptors from rat cere-bral cortex.The pharmacological activities were assessed in three individual experi-ments: (1) potentiating the effect of subthreshold hypnotic dose of sodium pentobarbital; (2) inhibiting oxotremorine-induced salivation; and (3) inhibiting the contractile response to carbachol. Results: The order of potency of phency- nonate hydrochloride and its (K_i = 46.49 ± 1.27 nmol / L)> CPG (K_i = 271.37 ± 72.30 nmol / L) )> S (+) - CPG (K_i = 1263.12 ± 131.64 nmol / L). The results showed thatR (-) - CPG had the highest affinity to central muscarinic receptors among the three compounds, but did not show any central depressant effects at dose from 10.00 to 29.15 mg / kg. CPG increased the effects of subthreshold hypnotic dose of sodium pentobarbital induced-sleeping [the ED 50 ± 95% LC value was 21.06 ± 3.04 mg / kg]. CPGand R (-) - CPG displayed nearly equipotent effect in depressing oxotremorine-induced salivation [the ED 50 ± 95% LC for R (-) and CPG were 1.10 ± 0.28 and 1.07 ± 0.15 mg / kg, (+) - CPG presents the lówestanticholinergic profiles, but could potentate effects of its enantiomers in somemanner. Conclusions: These data suggest that R (-) - CPG acted as an eutomerin racemate and a competitive antagonist to acetylcholine muscarinic receptors, but S (+) - CPG was less active in comparison to R (-) - CPG and its racemate.Thecentral depressant effects of R (-) - CPG and S (+) - CPG were lower in comparison to raceme.