Table 3.

Cumulative concentration-activity curve in guinea pig heart preparations. Cardiac activity and potency of sweet chestnut bark extract.

Compound	Positive inotropy				Negative chronotropy
	Left atria		Left papillary muscle		Right atria
	Activitya	Potencyb	Activityc	Potencyb	Activityd	Potencyb
Extract	45 ± 0.7	—	52 ± 1.9	0.09 (c.l. 0.07–0.13)	48 ± 1.3	—

^aIncrease in developed tension on isolated guinea pig left atrium at 1 mg/mL extract concentration, expressed as percent changes from the control (n = 5-6). Data represent mean ± S.E.M. The left atria were driven at 1 Hz. 1 mg/mL extract concentration gave the maximum effect.

^bThe EC₅₀ was expressed as mg/mL concentration that gave the 50% of the effect and was calculated from concentration-response curves (Probit analysis by Litchfield and Wilcoxon with n = 6-7).

^cIncrease in developed tension on isolated guinea pig left papillary muscle at 1 mg/mL extract concentration, expressed as percent changes from the control (n = 5-6). The left papillary muscle was driven at 1 Hz. 1 mg/mL gave the maximum effect for extract. Data represent mean ± S.E.M.

^dDecrease in atrial rate on guinea pig spontaneously beating isolated right atrium at 1 mg/mL extract concentration, expressed as percent changes from the control (n = 7-8). Data represent mean ± S.E.M. Pretreatment heart rate ranged from 165 to 190 beats/min. 1 mg/mL gave the maximum effect for extract.