Modulation of corticospinal excitability by valerian officinalis root extract: A neuropharmacological Transcranial Magnetic Stimulation (TMS) study

Abstract

IntroductionValerian officinalis roots extract is a popular medication for insomnia and anxiety treatment. Sedative effect of Valerian is mainly attributed to the modulation of gabaergic transmission, but its pharmacodynamics has not been fully elucidated.ObjectsTo investigate the acute effects of Valerian Officinalis extracts intake on corticoexcitability as measured by TMS.AimsTo obtain further data on Valerian pharmacodynamics.MethodsTwelve healthy volunteers participated in a double-blind randomized crossover placebo-controlled study. They were required to take either 900 mg of Valerian officinalis extract (valerenic acid 0.8%) or placebo. Focal TMS of the hand area of left motor cortex was used to test Resting motor threshold (RMT), Motor evoked potentials (MEPs) amplitude and silent period duration (SP). We also tested Short-interval Intracortical Inhibition (SICI), Intracortical facilitation (ICF), Short and Long afferent Inhibition (SAI and LAI). All parameters were investigated at baseline, 1 hour and 6 hours after drug intake. After a 3-week washout period the subjects switched to the alternate arm of the study.ResultsA mixed RMANOVA revealed a significant main effect of “time” [F(1,22) = 4.03, P = 0.02] and a significant “treatment × time” interaction [F(1,22) = 6.3, P = 0.003]. Post-hoc analysis indicated that the amount of ICF was significantly reduced 1 hour after Valerian intake (P = 0.01) returning to baseline values after 6 hours. No significant changes between the Valerian and placebo groups were observed for the other parameters investigated.ConclusionsThe modulation of ICF induced by Valerian officinalis is likely due to glutamatergic antagonism and might underlie the anti-anxiety therapeutic effects.Disclosure of interestThe authors have not supplied their declaration of competing interest.