HUMULUS LUPULUS (HOPS), IS THERE ANY EVIDENCE FOR CENTRAL NERVOUS EFFECTS RELATED TO SLEEP?

Abstract

Hops are traditionally used as a mild sedative for anxiety, nervousness, and insomnia even though their sedative and sleep-promoting activities are poorly understood. In vitro experiments of hops extract demonstrated binding activities to serotonin and melatonin receptors. Additionally there are hints that hops extract modulates the γ-aminobutyric acid (GABA) action on the GABA channel. In behavioural tests spontaneous and explorative activity was reduced. In addition, hops extract prolongs the narcotic induced sleeping time indicating a sedation activity. However, the behaviour of small rodents in the plus maze test remains unchanged therefore an anxiolytic action is unlikely. Furthermore hops extract induced a reduction in the body core temperature like melatonin which can be prevented by prior administration of luzindole, a competitive melatonin receptor antagonist. Both of the actions, i.e., sedation and hypothermic action are possibly induced by distinguishable components in the hops extract indicating that there are at least two active principles included in the hops extract. Clinical trials are available for a fixed hops valerian extract combination. Administration in patients suffering from non-organic sleep disturbances showed reduction of sleep latency and wake after sleep onset together with an enlargement of the slow wave sleep. In another study the influence of the fixed extract combination on the prolonged sleep latency was investigated. Valerian alone was not superior to placebo but adding the hops extract, the fixed extract combination was superior to placebo in reduction of the prolonged sleep latency.