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Abstract

Background: Neurexan®, a natural pharmaceutical product, is composed of passionflower, oats, coffee and zinc valerianate. It has been investigated in acute stressed patients and patients with insomnia. Stress initiates changes in functional connectivity (FC) between amygdala and cortical regions. The functional integrity can be assessed via amygdala-centered resting-state (rs) FC. Amygdala is involved in developing fear and emotions. Amygdala reactivity to negative stimuli associates with stress regulation and can be assessed with the Hariri paradigm. Previous studies reported associations between ongoing variability in Autonomous Nervous System (ANS) tone measured by heart rate variability (HRV) and stress-induced changes in dACC and amygdala FC. Question: Does Neurexan® affect emotional brain response to stress? Method: Thirty-nine healthy male subjects participated in a double-blind, randomized, placebo-controlled, within-subject cross-over fMRI study assessing Neurexan® effects at 3 Tesla. In each session, an 11 min rs-measurement was performed at baseline, after single dose of Neurexan® or placebo and after exposure to psychosocial stress. The emotional Hariri paradigm was measured after intake of verum or placebo. HRV was recorded continuously during the sessions. Data were preprocessed and analyzed in SPM12 and DPABI. Results: Significant effect of Neurexan® was found on rs-FC between left centromedial amygdala and cortical regions. In the Hariri task, paired t-test showed a drug effect in left amygdala, with stronger activations in placebo than Neurexan® condition. Comparing Neurexan® and placebo groups, Neurexan® improved variability in ANS tone in both conditions, prior and after psychosocial stress, compared to baseline. Discussion: We saw a beneficial effect of Neurexan® on stress-induced brain function.