Neuropharmacological activity of Humulus lupulus L.

The traditional use of hops in the treatment of sleep disturbances has been supported by experimental studies performed in rodents, as described in the present chapter. An inhibitory influence on the central nervous system was suggested by the finding of a reduction in locomotor behavior together with an enhancement of pentobarbital hypnotic activity, following the oral administration of hop extracts. A lipophilic hop extract showedan antidepressant-like activity in an animal model of behavioral despair, without a significant anxiolytic activity. Among hop components, the bitter acids have been carefully investigated for their role in the neuropharmacological activities of hops. In particular, the fraction containing alfa -acids has been recognizedto be mainly responsible for the sedative effects of hops. On the other hand the fraction containing beta -acids appears to exert a central stimulatory activity, probably due to a reduction in the GABAergic activity. This hypothesis is supported by its effects in animal models of sedation and convulsions as well as in electrophysiological studies on cerebellar granule cells in culture.Clinical trials specifically related to the sedative properties of hops are still inadequate since human studies were mainly performed using valerian–hop combination extracts.