2.4. In Vitro—Isolated Contractility Study

The uteri of 22-day pregnant Sprague-Dawley rats were dissected, the fetuses were removed, and the uteri were sliced into 0.5-cm-long rings. The smooth muscle tissues were mounted vertically in an organ bath containing 10 mL of de Jong solution (composition in mM: 137 NaCl, 3 KCl, 1 CaCl₂, 1 MgCl₂, 12 NaHCO₃, 4 NaH₂PO₄, 6 glucose, pH 7.4). The temperature of the organ bath was maintained at 37 °C with a continuous carbogen (95% O₂ + 5% CO₂) supply.

The initial tension of the uterine rings was set about 1.5 g, the equilibration time was 60 min with a buffer change every 15 min. The contractions of the 22-day myometrial rings were measured with a gauge transducer (SG-02) and recorded with a SPEL Advanced ISOSYS Data Acquisition System (MDE Ltd., Budapest, Hungary). The rhythmic uterine contractions were elicited by 25 mM KCl and the cumulative concentration-response curve of citral (10⁻⁸–10⁻² M) was obtained.