Evidence that the beta-acids fraction of hops reduces central GABAergic neurotransmission.
Humulus lupulus (hops) is traditionally used as a tranquilizing herbal remedy. Here, we investigated the in vivo and in vitro effect of hop beta-acids on central nervous system function. Oral administration of beta-acids (5-10mg/kg) in rats produced an increased exploratory activity in the open field, a reduction in the pentobarbital hypnotic activity and a worsening of picrotoxin-induced seizures. When dosed at 10mg/kg, beta-acids increased, in the elevated plus maze, open arm entries reducing in parallel those in closed arms. In the forced swimming test, we observed a reduction in the immobility time that could suggest an antidepressant-like activity. Electrophysiological studies performed on cerebellar granule cells in culture showed that the beta-acids fraction decreased GABA-evoked current in a dose-dependent way. The effect was not inhibited by the benzodiazepine antagonist Ro 15-1788. Benzodiazepine receptors involvement was also excluded by [(3)H]-Ro 15-1788 binding assay. In conclusion, the behavioral effects of beta-acids fraction could be explained by a reduction in the GABAergic activity although we cannot rule out the involvement of other neurotransmitter systems.
Zanoli
P
P
Department of Biomedical Sciences, Section of Pharmacology, National InterUniversity Consortium for the Study of Natural Active Principles (CINSPAN), University of Modena and Reggio Emilia, 41100 Modena, Italy. zanoli.paola@unimore.it
Zavatti
M
M
Rivasi
M
M
Brusiani
F
F
Losi
G
G
Puia
G
G
Avallone
R
R
Baraldi
M
M
D000818:Animals; D000928:Antidepressive Agents / Q000494:pharmacology; D001667:Binding, Competitive / Q000187:drug effects; D002245:Carbon Dioxide; D002490:Central Nervous System / Q000187:drug effects; D002531:Cerebellum / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D003864:Depression, Chemical; D004594:Electrophysiology; D018756:GABA Antagonists; D027582:Humulus / Q000737:chemistry*; D008297:Male; D018782:Maze Learning / Q000187:drug effects; D009043:Motor Activity / Q000187:drug effects; D010424:Pentobarbital / Q000494:pharmacology; D010852:Picrotoxin; D010936:Plant Extracts / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011963:Receptors, GABA-A / Q000187:drug effects; D012640:Seizures / Q000139:chemically induced / Q000517:prevention & control; D012890:Sleep / Q000187:drug effects; D012997:Solvents; D013550:Swimming / Q000523:psychology; D009435:Synaptic Transmission / Q000187:drug effects*; D005680:gamma-Aminobutyric Acid / Q000502:physiology*
D000928:Antidepressive Agents; D002245:Carbon Dioxide; D018756:GABA Antagonists; D010424:Pentobarbital; D010852:Picrotoxin; D010936:Plant Extracts; D011963:Receptors, GABA-A; D012997:Solvents; D005680:gamma-Aminobutyric Acid