Honokiol

Prostate strips (6 mm×3 mm×3 mm) were mounted in 10 mL aerated (95% O2 and 5% CO2) tissue baths (Föhr Medical Instruments, Seeheim, Germany), containing Krebs-Henseleit solution (37°C, pH 7.4). Preparations were stretched to 0.5 g and left to equilibrate for 45 minutes. In the initial phase of the equilibration period, spontaneous decreases in tone are usually observed. Therefore, tension was adjusted three times during the equilibration period, until a stable resting tone (0.5 g) was attained. After the equilibration period, maximum contraction induced by 80mM KCl (Krebs-Henseleit solution where NaCl was exchanged by KCl) was assessed. Subsequently, chambers were washed three times with Krebs-Henseleit solution for a total of 30 minutes. Cumulative concentraction response curves for noradrenaline or phenylephrine (both from Sigma-Aldrich, Munich, Germany) were created after addition of 100μM honokiol, 100μM magnolol (both from Santa Cruz Biotechnology Inc., Santa Cruz, CA, USA), or an equivalent volume of solvent (dimethylsulfoxide, DMSO). Fequency response curves induced by electric field stimulation (EFS) were created before and after addition of inhibitors or solvent (DMSO for honokiol, water for tamsulosin, and DMSO for the combination of both). Inibitors or DMSO were applied 45 minutes before concentration or frequency response curves.