Opposite Neurophysiological Findings Induced by <i>Sideritis scardica</i> and <i>Sideritis euboa</i> Extract in the Rat

Abstract

Psychophysiological effects of Sideritis herba extracts depend on biologically active ingredients, which might be different for several botanical types of this plant. The present investigation aimed at the characterization of extracts from <i>Sideritis scardica</i> and <i>Sideritis euboa</i> <i>in vivo</i> and <i>in vitro</i>. Construction of electropharmacograms on the base of recording of electrical field potentials from four different brain regions was used to compare the possible pharmacological effects to a database of reference drugs with known clinical indications. Whereas <i>Sideritis scardica</i> produced decreases of spectral power in line with stimulatory frequency patterns as observed in the presence of Ginkgo biloba extract, administration of <i>Sideritis euboa</i> produced opposite effects. Electrical stimulation of the Schaffer Collaterals was used to elicit a pyramidal cell response called population spike <i>in vitro</i>. The amplitude of this spike was determined in the presence of single as well as theta burst stimuli. Direct exposure of brain matter to <i>Sideritis scardica</i> extract led to concentration dependent increases of the population spike amplitude under both stimulation patterns in the range from 12.5 to 100 mg/L. On the opposite, extract from <i>Sideritis euboa</i> did not change the electric response up to 50 mg/L. Higher concentrations of this extract attenuated the signal amplitude. A 1:1 blend of both gave intermediate results. The in vitro results are in line with the in vivo EEG recordings, where both extracts induced opposite changes of the electric power with respect to electric frequency patterns. The results from both models suggest a stimulatory and/or memory-enhancing action for the extract from <i>Sideritis scardica</i> but not for <i>Sideritis euboa</i> extract, where a more tranquillizing effect like that observed in the presence of Humulus cone extract may be expected.