Essential oil of Lippia alba and its main constituent citral block the excitability of rat sciatic nerves

Lippia alba is empirically used for infusions, teas, macerates, and hydroalcoholic extracts because of its antispasmodic, analgesic, sedative, and anxiolytic effects. Citral is a mixture of trans-geranial and cis-neral and is the main constituent of L. alba essential oil and possesses analgesic, anxiolytic, anticonvulsant, and sedative effects. The present study evaluated the effects of the essential oil of L. alba (EOLa) and citral on compound action potentials (CAPs) in Wistar rat sciatic nerves. Both drugs inhibited CAP in a concentration-dependent manner. The calculated half-maximal inhibitory concentrations (IC50) of peak-to-peak amplitude were 53.2 µg/mL and 35.00 µg/mL (or 230 µM) for EOLa and citral, respectively. Peak-to-peak amplitude of the CAP was significantly reduced by 30 µg/mL EOLa and 10 µg/mL citral. EOLa and citral (at 60 and 30 µg/mL, values close to their respective IC50 for CAP blockade) significantly increased chronaxy and rheobase. The conduction velocity of the first and second CAP components was statistically reduced to ∼86% of control with 10 µg/mL EOLa and ∼90% of control with 3 µg/mL citral. This study showed that EOLa inhibited nerve excitability and this effect can be explained by the presence of citral in its composition. Both EOLa and citral showed inhibitory actions at lower concentrations compared with other essential oils and constituents with local anesthetic activity. In conclusion, these data demonstrate that EOLa and citral are promising agents in the development of new drugs with local anesthetic activity.

Differentiating origins of outflow tract ventricular arrhythmias: a comparison of three different electrocardiographic algorithms

Our objective is to evaluate the accuracy of three algorithms in differentiating the origins of outflow tract ventricular arrhythmias (OTVAs). This study involved 110 consecutive patients with OTVAs for whom a standard 12-lead surface electrocardiogram (ECG) showed typical left bundle branch block morphology with an inferior axis. All the ECG tracings were retrospectively analyzed using the following three recently published ECG algorithms: 1) the transitional zone (TZ) index, 2) the V2 transition ratio, and 3) V2 R wave duration and R/S wave amplitude indices. Considering all patients, the V2 transition ratio had the highest sensitivity (92.3%), while the R wave duration and R/S wave amplitude indices in V2 had the highest specificity (93.9%). The latter finding had a maximal area under the ROC curve of 0.925. In patients with left ventricular (LV) rotation, the V2 transition ratio had the highest sensitivity (94.1%), while the R wave duration and R/S wave amplitude indices in V2 had the highest specificity (87.5%). The former finding had a maximal area under the ROC curve of 0.892. All three published ECG algorithms are effective in differentiating the origin of OTVAs, while the V2 transition ratio, and the V2 R wave duration and R/S wave amplitude indices are the most sensitive and specific algorithms, respectively. Amongst all of the patients, the V2 R wave duration and R/S wave amplitude algorithm had the maximal area under the ROC curve, but in patients with LV rotation the V2 transition ratio algorithm had the maximum area under the ROC curve.