Exploring the effect of adaptogenic Rhodiola Rosea extract on neuroplasticity in humans.

OBJECTIVES: Rhodiola rosea extract is one of the most common herbal treatment for stress. Its mechanism of action in humans still need to be determined. We investigated the effect of a single dose intake of Rhodiola rosea extract on the plastic after-effects induced by anodal and cathodal motor cortex transcranial Direct Current Stimulation in humans. METHODS: Twenty-eight healthy volunteers were required to intake 500 mg of either RRE or placebo. Transcranial Magnetic Stimulation was used to investigate cortical excitability. Motor threshold, recruitment of motor-evoked potentials, cortical silent period, short-interval intracortical inhibition and intracortical facilitation were assessed at different time points. Spinal excitability and peripheral nerve conduction were measured by F-response and M-wave. Furthermore, we assessed the modulation of cortical plasticity using transcranial direct current stimulation after-effects on Motor Evoked Potentials amplitudes. RESULTS: Rhodiola rosea extract acute intake prevented cathodal transcranial Direct Current Stimulation-induced Long-term depression-like plasticity. The extract intake did not affect cortical excitability. CONCLUSIONS: Our findings suggest that a single oral dose of Rhodiola rosea extract intake modulates cortical plasticity in humans preventing the activity-dependent reduction in the efficacy of neuronal synapses. These results suggest that the adaptogenic and antidepressant effects of Rhodiola rosea extract might be based on its modulation of brain plasticity.

Hypericum perforatum extract modulates cortical plasticity in humans.

BACKGROUND: Hypericum perforatum (HYP) extract is one of the most commonly used complementary alternative medicines (CAMs) for the treatment of mild-to-moderate depression. Non-invasive brain stimulation protocols can be used to investigate the effect of psychoactive substances on the human brain. In this study, we explored the effect of a single dose of HYP extract (WS 5570) intake on corticospinal excitability and plasticity in humans. METHODS: Twenty-eight healthy subjects were required to intake 900 mg of either HYP extract or placebo. Cortical excitability was assessed using single and paired transcranial magnetic stimulation (TMS). The electrophysiological parameters of motor threshold, recruitment of motor-evoked potentials (MEPs), cortical silent period (CSP), short interval intracortical inhibition (SICI), and intracortical facilitation (ICF) were tested before and 2 and 5 h after the oral intake. Spinal and neuromuscular excitability and peripheral nerve excitability were measured by F response and M-wave. Cortical plasticity was induced using transcranial direct current stimulation (tDCS). Subjects received either HYP extract or placebo before anodal and cathodal tDCS of the primary motor cortex. Plasticity was assessed by MEP amplitudes. RESULTS: HYP extract reversed cathodal tDCS-induced long-term depression (LTD)-like plasticity into facilitation, as compared to placebo. HYP extract did not have a significant effect on anodal tDCS-induced plasticity and TMS measures of motor cortex and spinal/neuromuscular excitability. CONCLUSIONS: Our findings suggest that a single oral dose of HYP extract modulates cortical plasticity in healthy subjects and provide new insight into its possible mechanism of action in humans.

Valeriana officinalis Root Extract Modulates Cortical Excitatory Circuits in Humans.

BACKGROUND: Valeriana officinalis extract (VE) is a popular herbal medicine used for the treatment of anxiety and sleep disorders. Although the anxiolytic and sedative effects are mainly attributed to the modulation of GABA-ergic transmission, the mechanism of action has not been fully investigated in humans. Noninvasive brain stimulation protocols can be used to elucidate the mechanisms of action of psychoactive substances at the cortical level in humans. In this study, we investigated the effects of a single dose of VE on cortical excitability as assessed with transcranial magnetic stimulation (TMS). METHODS: Fifteen healthy volunteers participated in a double-blind, randomized, cross-over, placebo-controlled study. Subjects were required to take either 900 mg of VE (valerenic acid 0.8%) or placebo (an equal dose of vitamin E). Motor cortex excitability was studied by single and paired TMS before and at 1 h and 6 h after the oral administration. Cortical excitability was assessed using different TMS parameters: resting motor threshold, motor-evoked potential amplitude, cortical silent period, short-interval intracortical inhibition, and intracortical facilitation. Furthermore, we assessed sensorimotor integration by short-latency and long-latency afferent inhibition. RESULTS: We found a significant reduction in ICF, without any significant changes in other TMS measures of motor cortex excitability. The amount of ICF returned to baseline value 6 h after the intake of the VE. CONCLUSION: A single oral dose of VE modulates intracortical facilitatory circuits. Our results in healthy subjects could be predictive markers of treatment response in patients and further support the use of pharmaco-TMS to investigate the neuropsychiatric effects of herbal therapies in humans.

Perceived Stress and Coffee and Energy Drink Consumption Predict Poor Sleep Quality in Podiatric Medical Students A Cross-sectional Study.

BACKGROUND: A cross-sectional survey administered to first- and second-year podiatric medical students aimed to investigate the effect of coffee intake, energy drink consumption, and perceived stress on sleep quality in medical students during their preclinical studies. METHODS: Ninety-eight of 183 students contacted (53.6%) completed a questionnaire comprising standard instruments measuring sleep quality (Pittsburgh Sleep Quality Index), daytime sleepiness (Epworth Sleepiness scale), and perceived stress (ten-item Perceived Stress Scale). Furthermore, we investigated coffee and energy drink consumption. Logistic regression was conducted to identify factors associated with poor sleep quality and the relation between sleep quality and academic performance (grade point average). RESULTS: High prevalences of poor sleep quality, excessive daytime sleepiness, and perceived stress were reported. In addition, higher odds of developing poor sleep quality were associated with coffee and energy drink intake, perceived stress, and excessive daytime sleepiness. The total Pittsburgh Sleep Quality Index score was inversely correlated with grade point average. CONCLUSIONS: First- and second-year podiatric medical students have poor sleep quality. Further research is needed to identify effective strategies to reduce stress and decrease coffee and energy drink intake to minimize their negative effect on sleep quality and academic performance in podiatric medical students.