The Effects of Extracts from St. John's Wort and Kava Kava on Brain Neurotransmitter Levels in the Mouse

Introduction

Extracts of Hypericum perforatum (St. John's Wort, SJW) and Kava Kava are well established in the treatment of psychiatric disorders. Several controlled clinical studies have confirmed that SJW extract represents an effective antidepressant principle superior to placebo [13] [18] [19]. SJW extract contains at least ten constituents or groups of components that may contribute to its pharmacological effects [4]. SJW extracts have been shown to inhibit synaptosomal uptake of serotonin, dopamine and noradrenaline, implying a biochemical mechanism similar to classical antidepressants [14] [15]. The reuptake inhibiting properties of SJW extract have mostly been attributed to the phloroglucinol derivative, hyperforin [15]; see also Wonnemann et al., this issue.

Kava Kava extract is made from the root of Piper methysticum, which is found in the south Pacific region. Clinically, Kava Kava is used for anxiety and insomnia in Europe and the United States. One meta-analysis of various trials has implied that Kava Kava extract is superior to placebo as a symptomatic treatment for anxiety [16]. A number of compounds, referred to as Kava pyrones, are thought to be responsible for the plant's effects. Although Kava pyrones exert weak effects on benzodiazepine-binding sites in vitro, the biochemical mechanism of action is not yet known [7].

In the present study, we will address the question of whether acute oral treatment of mice with SJW or Kava Kava extracts alters neurotransmitter levels in the brain. Brain levels of different neurotransmitters and their metabolites were determined in brain homogenates using high-performance liquid chromatography with electrochemical detection.

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