Hypericum extract and hyperforin: memory-enhancing properties in rodents.
Effects of a Hypericum extract in therapeutic use and hyperforin sodium salt were evaluated in rat and mouse avoidance tests. In a conditioned avoidance response (CAR) test on the rat, oral daily administration of hyperforin (1.25 mg/kg/day) or of the extract (50 mg/kg/day) before the training sessions considerably improved learning ability from the second day onwards until the day 7. In addition, the memory of the learned responses acquired during 7 consecutive days of administration and training was largely retained even after 9 days without further treatment or training. The observations made using different doses indicate that these learning-facilitating and/or memory-consolidating effects by the agents follow inverse U-shaped dose-response curves in dose ranges lower than (for hyperforin) or equal to (for Hypericum extract) their effective dose in the behavioral despair test for antidepressants. In a passive avoidance response test on the mouse, a single oral dose (1.25 mg/kg) of hyperforin not only improved memory acquisition and consolidation, but also almost completely reversed scopolamine-induced amnesia. The single Hypericum extract dose tested (25 mg/kg) did not reveal any significant effects in the passive avoidance response (PAR) test on the mouse. These observations suggest that the Hypericum extract could be a novel type of antidepressant with memory enhancing properties, and indicate that hyperforin is involved in its cognitive effects. Pure hyperforin seems to be a more potent antidementia agent than an antidepressant.
Klusa
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Department of Pharmacology, Faculty of Medicine, University of Latvia, Riga. vijaklus@acad.latnet.lv
Germane
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Nöldner
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M
Chatterjee
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SS
D000647:Amnesia / Q000139:chemically induced / Q000188:drug therapy; D000818:Animals; D000928:Antidepressive Agents / Q000494:pharmacology*; D001362:Avoidance Learning / Q000187:drug effects; D001522:Behavior, Animal / Q000187:drug effects; D001643:Bridged Bicyclo Compounds; D020902:Hypericum; D008297:Male; D008568:Memory / Q000187:drug effects*; D051379:Mice; D008807:Mice, Inbred BALB C; D018727:Muscarinic Antagonists; D010696:Phloroglucinol / Q000031:analogs & derivatives; D010936:Plant Extracts / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D012601:Scopolamine; D013729:Terpenes / Q000494:pharmacology*
D000928:Antidepressive Agents; D001643:Bridged Bicyclo Compounds; D018727:Muscarinic Antagonists; D010936:Plant Extracts; D013729:Terpenes; D010696:Phloroglucinol; D012601:Scopolamine; C001654:hyperforin