Triethylene glycol-like effects of Ashwagandha (Withania somnifera (L.) Dunal) root extract devoid of withanolides in stressed mice.

BACKGROUND: The objective of the study is to compare stress resistance-promoting effect of triethylene glycol (TEG) and root extract of Ashwagandha (Withania somnifera) i.e. withanolide-free root extract of Withania somnifera (WFWS). MATERIALS AND METHODS: Mice groups treated orally with 10 mg/kg TEG or WFWS (3.3, 10, 33.3, or 100 mg/kg) for 12 consecutive days were subjected to foot shock stress-triggered hyperthermia test on the 1st, 5th, 7th and 10th day and to marble-burying test on the following 2 days. Effects of treatment on stress-triggered alteration in body weight, core temperature, blood glucose, insulin and cortisol level were quantified and statistically analyzed. RESULTS: WFWS doses up to 10 mg/kg/day were as effective as TEG in affording protection against stress-triggered alteration in body weight, core temperature and marble-burying behavior. Protection against stress-triggered alteration in blood glucose and insulin level, as well as antidepressants or anxiolytic-like activities in the behavioral test, were observed in the higher two WFWS doses (33.3 and 100 mg/kg) treated groups only. CONCLUSION: Ashwagandha metabolites other than withanolides contribute to its stress resistance increasing effects. The observations suggest that modulation of physiological functions of gut microbiota may be involved in the mode of action of Withania somnifera root extracts.

Effects of turmeric curcuminoids and metformin against central sensitivity to pain in mice.

The reported experimental study was conducted to compare the effects of repeated daily oral doses of curcuminoids (CLE) with metformin as potential antidepressants and analgesics. Effects of a single and ten daily oral doses of CLE (5, 20, 80 mg/kg/day) and of 50 mg/kg/day metformin (MET) were compared in mice hot plate test (HPT) for analgesics. On the 11th treatment day, all animals were subjected to foot shock stress triggered hyperthermia test, and on the 12th treatment day to tail suspension test (TST) for antidepressants. Immediately thereafter, their blood levels of glucose, insulin and cortisol were quantified. Dose dependent analgesic activity of CLE was observed in HPT, whereas the metformin dose tested suppressed only pain hypersensitivity in the test. But statistically significant effects of both of them were observed in TST, and both of them also afforded protections against body weight loss and slight elevation in core temperatures induced by daily handling and repeated testing. CLE or metformin had no significant effects in foot shock stress triggered transient hyperthermic responses or on blood glucose, insulin and cortisol levels. Reported results reveal that curcuminoids as well as metformin are stress response modifiers with antidepressants like activities, but only low dose curcuminoids possess centrally acting analgesics like activities. They suggest that the bio-assay system used in this study is well suited for identifying curcuminoids like plant metabolites with analgesic and anti-stress activities, and that low dose curcuminoids are more effective as analgesics than low dose metformin.

Preventive potentials of piperlongumine and a Piper longum extract against stress responses and pain.

AIM: To compare stress resistance increasing and analgesic activities of piperlongumine and a methanolic Piper longum fruit extract (PLE). METHODS: Efficacies of a single and repeated daily oral doses (1-256 mg/kg/day) of PLE, piperlongumine, and 50 mg/kg/day doxycycline against foot shock stress triggered alteration in body weights and core temperatures, and of their 11 daily doses on antidepressants like activity in tail suspension test and on pentobarbital induced sedation in male mice were compared. In another experiment, analgesic activities of single and repeated daily 5 mg/kg oral doses of piperlongumine and PLE in mice hot plate test and in acetic acid induced writing tests were compared with those of aspirin and doxycycline. RESULTS: After their single oral doses no effects of piperlongumine or PLE or doxycycline were observed in the footshock stress induced hyperthermia test or in hot plate test. However, significant effects of piperlongumine and PLE in both the tests were observed after their 5 or more daily doses. Both of them also dose dependently suppressed daily handling and repetitive testing triggered alterations in body weights and core temperatures. Their doxycycline like antidepressant activity in tail suspension test and aspirin like analgesic effects in acetic acid writhing test were observed after their 11 daily 5 mg/kg oral dose. CONCLUSION: Piperlongumine is another bioactive secondary metabolite of P. longum and other plants of piper species with stress response suppressing, analgesic, and anti-inflammatory activities. Its bactericidal activities can also contribute to its therapeutically interesting bio-activity profile.

Low dose effects of a Withania somnifera extract on altered marble burying behavior in stressed mice.

AIM: Withania somnifera root (WSR) extracts are often used in traditionally known Indian systems of medicine for prevention and cure of psychosomatic disorders. The reported experiment was designed to test whether low daily oral doses of such extracts are also effective in suppressing marble burying behavior in stressed mice or not. MATERIALS AND METHODS: Groups of mice treated with 10, 20, or 40 mg/kg daily oral doses of WSR were subjected to a foot shock stress-induced hyperthermia test on the 1(st), 5(th), 7(th), and 10(th) day of the experiment. On the 11(th) and 12(th) treatment days, they were subjected to marble burying tests. Stress response suppressing effects of low dose WSR were estimated by its effects on body weight and basal core temperature of animals during the course of the experiment. RESULTS: Alterations in bodyweight and basal core temperature triggered by repeated exposures to foot shock stress were absent even in the 10 mg/kg/day WSR treated group, whereas the effectiveness of the extract in foot shock stress-induced hyperthermia and marble burying tests increased with its increasing daily dose. CONCLUSION: Marble burying test in stressed mice is well suited for identifying bioactive constituents of W. somnifera like medicinal plants with adaptogenic, anxiolytic and antidepressant activities, or for quantifying pharmacological interactions between them.

Low dose aspirin like analgesic and anti-inflammatory activities of mono-hydroxybenzoic acids in stressed rodents.

AIMS: To compare analgesic and anti-inflammatory activities of aspirin and mono-hydroxybenzoic acids after their daily oral doses. MAIN METHODS: Efficacies of repeated daily stress response suppressing low oral doses (20mg/kg) of aspirin and 2-, 3-, and 4-hydroxybenzoic acids in mice hot plate test for centrally acting analgesics, and in acetic acid induced writing test were compared. Effects of their same daily doses and treatment regimen in cotton pellet granuloma and carrageenan edema test for anti-inflammatory drugs in stressed rats were compared in a second experiment. Effects of treatments on body weights, basal rectal temperatures, organ weights and plasma glucose, insulin and cortisol levels in stressed animals were compared also. KEY FINDINGS: Although stress response suppressing effects of aspirin and all the three hydroxybenzoic acids in both mice and rats were almost equal, effectiveness of 3- and 4-hydroxybenzoic acids as analgesic and anti-inflammatory agents were lower than those of aspirin or salicylic acid. SIGNIFICANCE: Observations made after single oral doses of aspirin or of mono-hydroxybenzoic acids are not very reliable predictors of their pharmacologically interesting bioactivity profiles and efficacies. Prostaglandin synthesis inhibition is not involved in low dose anti-inflammatory activities of 3- and 4-hydroxybenzoic acids. After their repeated daily low oral doses they are almost as potent stress response desensitizers as aspirin or salicylic acid.

Beneficial effects of an Andrographis paniculata extract and andrographolide on cognitive functions in streptozotocin-induced diabetic rats.

Context Andrographolide containing Andrographis paniculata (Burm. F.) Wall. Ex Nees (Acanthaceae) extracts is often used for treatments of diabetes and other inflammatory disorders commonly accompanying cognitive and other psychiatric disorders. Objective To compare the efficacies of a standardised A. paniculata extract (AP) and pure andrographolide on cognitive functions, oxidative stress and cholinergic function in diabetic rats. Materials and methods Streptozotocin-induced diabetic Charles Foster albino rats treated orally with a hydro-methanolic A. paniculata leaf extract (50, 100 and 200 mg/kg/day), or with pure andrographolide (15, 30 and 60 mg/kg/day) for 10 consecutive days, were subjected to Morris water maze test. After the test, acetylcholinesterase, superoxide dismutase (SOD), and catalase (CAT) activities and lipid peroxidation (LPO) in brain tissues were assessed. Results Acetylcholinesterase activity in pre-frontal cortex and hippocampus of diabetic rats was 2.1 and 2.6 times higher compared to nondiabetic rats. LPO was 1.6 times higher and decreased SOD (56.3%) and CAT (44.9%) activities in pre-frontal cortex of diabetic rats compared to nondiabetic rats. AP or andrographolide treatments dose dependently attenuated cognitive deficits, reduced acetylcholinesterase activity, oxidative stress, improved diabetic hyperglycemia and insulin deficiency. All observed effects of AP were quantitatively almost equal to those expected from its analytically quantified andrographolide content. Discussion and conclusion Reported observations are the very first ones suggesting beneficial effects of andrographolide against diabetes associated cognitive deficits, increased acetylcholinesterase activity and deteriorated antioxidative status. Efforts to exploit A. paniculata extracts enriched in andrographolide as preventive measures against such disorders can be warranted.

Gastro-protective and Anti-stress Efficacies of Monomethyl Fumarate and a Fumaria indica Extract in Chronically Stressed Rats.

Results of the very first experiments conducted to evaluate therapeutic potentials of a fumarate containing Fumaria indica extract and of fairly low daily oral doses of monomethyl fumarate for prevention of chronic unavoidable foot-shock stress-induced gastric ulcers, and possible involvement of diverse neuro-hormonal and oxidative process in their stress response desensitizing effects are reported and discussed in this article. Preventive effects of 21 daily oral 60, 120, and 240 mg/kg doses of a standardized 50 % methanolic F. indica extract (MFI) and 1.25, 2.50, and 5.00 mg/kg/day of pure monomethyl fumarate (MMF) were compared in rats subjected to one hour daily unavoidable foot-shocks. A pharmaceutically well-standardized Withania somnifera (WS) root extract was used as a reference herbal anti-stress agent in all experiments. Effects of the treatments on stress-induced alterations in body weight, adrenal and spleen weights, gastric ulcer and ulcer index, weight of glandular stomach, protective mucosal glycoprotein content, cellular proliferation, oxidative stress on stomach fundus, and brain tissues of male rats were quantified. Other parameters quantified were plasma corticosterone levels, brain monoamine levels, and expressions of the cytokines TNF-α, IL-10, and IL-1ß in blood and brain of stressed and treated rats. Most but not every observed stress-induced anomalies were suppressed or completely prevented by both MFI and pure MMF treatments in dose-dependent manner. Qualitatively, the observed activity profiles of both of them were similar to those of WS dose tested. These results reveal that both MFI and MMF are potent gastro-protective agents against chronic unavoidable stress-induced ulcers and strongly suggest that they act as regulators or modulators of monoamine, corticosterone, and cytokine homeostasis.

Long lasting preventive effects of piperlongumine and a Piper longum extract against stress triggered pathologies in mice.

AIM: To compare doxycycline (DOX) such as oral efficacies of piperlongumine (PL) and a Piper longum fruits extract (PLE) as stress resistance inducers. MATERIALS AND METHODS: Efficacies of oral pretreatments with 5 mg/kg PL or PLE or of 50 mg/kg DOX for 10 consecutive days against stress resistance were compared. Mice in treated groups were subjected to a stress induced hyperthermia on the 1(st), 5(th), 7(th), and 10(th)day. Treated mice were then subjected to tail suspension test on the 11(th)day. Alteration in body weights, core temperatures, and gastric ulcers triggered by occasional exposures to foot shocks were determined. RESULTS: DOX like long-lasting protective effects of PL and PLE against gradual alterations in body weights, basal temperatures and transient hyperthermic responses triggered by foot shocks during the post-treatment days were observed. Altered responses of stressed mice in tail suspension test observed 1 day after the last foot-shock exposures and gastric ulcers and other pathologies quantified 1 day after the test were also suppressed in PL or PLE or DOX pretreated groups. CONCLUSION: PL and crude PLE are DOX like long-acting desensitizers of stress triggered co-morbidities. Reported observations add further experimental evidences justifying traditionally known medicinal uses of P. longum and other plants of the Piperaceae family, and reveal that PL is also another very long acting and orally active inducer of stress resistance. Efforts to confirm stress preventive potentials of low dose plant-derived products enriched in PL or piperine like amide alkaloids in volunteers and patients can be warranted.

From covalent bonds to eco-physiological pharmacology of secondary plant metabolites.

Despite the availability of numerous drugs and other therapeutic modalities, the prevention and cure of over- and under-nutrition triggered metabolic and other disease states continues as a major challenge for modern medicine. Such silently progressing and eventually life-threatening diseases often accompany diverse spectrum of comorbid psychiatric disorders. Majority of the global population suffering from metabolic diseases live in economically developing or underdeveloped countries, where due to socioeconomic, cultural, and other reasons, therapies may be unavailable. Evidence from preclinical, clinical, and epidemiological studies of numerous structurally and functionally diverse secondary metabolites of plants suggest that many of these could be promising therapeutic leads for the treatment and prevention of malnutrition-associated diseases and mental health problems. The review discusses the potential therapeutic uses of secondary plant metabolites and their bacterial and mammalian catabolites based on their bioactivity profiles, with special emphasis on their modulating effects on gut microbial ecology and physiological stress responses. Based on concepts in medicinal chemistry and pharmacology considerations that evolved during the author's interactions with David Triggle, secondary plant metabolites may represent an alternative and economically feasible approach to new drugs.

Adaptogenic potential of andrographolide: An active principle of the king of bitters (Andrographis paniculata).

Andrographolide is a major bioactive secondary plant metabolite isolated Andrographis paniculata (Burm. F.) Wall. Ex. Nees. ( chuan xin lián), a well-known traditionally used medicinal herb. The aim of the study was to pharmacologically evaluate the beneficial effect of andrographolide on stress-induced thermoregulatory and other physiological responses in mice. A stress-induced hyperthermia test was conducted in mice. The test agents were orally administered once daily for 11 consecutive days, and treatment effects on body weight changes, basal rectal temperature, and foot-shock-triggered hyperthermic responses were quantified on Day 1, Day 5, Day 7, and Day 10 of the experiments. Pentobarbital-induced hypnosis was quantified on the 11(th) day of treatment. Observations made during a pilot dose finding experiment revealed that, like A. paniculata extracts, pure andrographolide also possess adaptogenic properties. Observed dose-dependent efficacies of 3 mg/kg/d, 10 mg/kg/d, and 30 mg/kg/d andrographolide in the pilot experiment were reconfirmed by conducting two further analogous experiments using separate groups of either male or female mice. In these confirmatory experiments, efficacies of andrographolide were compared with that of 5 mg/kg/d oral doses of the standard anxiolytic diazepam. Significantly reduced body weights and elevated core temperatures of the three vehicle-treated control groups observed on the 5(th) day and subsequent observational days were completely absent even in the groups treated with the lowest andrographolide dose (3 mg/kg/d) or diazepam (5 mg/kg/d). Benzodiazepine-like potentiation of pentobarbital hypnosis was observed in andrographolide-treated animals. These observations reveal that andrographolide is functionally a diazepam-like desensitizer of biological mechanisms, and processes involved in stress trigger thermoregulatory and other physiological responses.

Protective effects of Andrographis paniculata extract and pure andrographolide against chronic stress-triggered pathologies in rats.

This study was designed to experimentally verify the possibility that Andrographis paniculata could be another medicinal herb potentially useful for prevention of diverse spectrums of pathologies commonly associated with chronic unavoidable environmental stress, and whether andrographolide could as well be its quantitatively major bioactive secondary metabolite. Preventive effects of 21 daily oral 50, 100 and 200 mg/kg doses of a therapeutically used extract of the plant (AP) and 30 and 60 mg/kg/day of pure andrographolide were compared in rats subjected to 1-h daily unavoidable foot-shocks. A pharmaceutically well-standardized Withania somnifera (WS) root extract was used as a reference herbal anti-stress agent in all experiments. Effects of the treatments on stress-induced alterations in body weight, gastric ulcer, adrenal and spleen weights, and depressive state and sexual behavior in male rats were quantified. Other parameters quantified were plasma cortisol levels, and expressions of the cytokines TNF-α, IL-10 and IL-1ß in blood and brain. All observed stress-induced pathological changes were less pronounced or completely prevented by both AP and pure andrographolide. Even the lowest tested doses of AP (50 mg/kg/day) or of andrographolide (30 mg/kg/day) suppressed almost maximally the blood IL-1ß and IL-10 as well as brain TNF-α and IL-10 expressions induced by chronic stress. Qualitatively, the observed activity profiles of both of them were similar to those of WS dose tested. These results reveal that both AP and andrographolide are pharmacologically polyvalent anti-stress agents, and that biological processes regulating corticosterone and cytokine homeostasis are involved in their modes of actions.

Antidepressant-like effects of Brassica juncea L. leaves in diabetic rodents.

The objective of the study was to evaluate for antidepressant like activity of a methanolic extract of B. juncea leaves (BJ 100, 200, and 400 mg/kg/day, po), and Imipramine (15 mg/kg/day, po) in alloxan monohydrate (120 mg/kg, ip) induced diabetic and nondiabetic rodents, using behavioural despair, learned helplessness, and tail suspension tests for antidepressants and locomotor activity test for quantifying the behavioural effects of treatments. In addition, effects of BJ treatments on brain levels of norepinephrine, serotonin and dopamine were also estimated. Enhanced depressive states, and motility were observed in diabetic animals. Antidepressant and motor function depressing effects of BJ were apparent in all behavioural tests in diabetic rats and mice only. Decreased contents of dopamine, norepinephrine and serotonin in brain of diabetic rats were also dose dependently compensated by repeated daily BJ treatments. However, brain dopamine level of BJ treated normal rats was higher than that in control nondiabetic. The results suggest that BJ could be a nutritional alternative for combating exaggerated depression commonly associated with diabetes.

Role of fumaric acid in anti-inflammatory and analgesic activities of a Fumaria indica extracts.

AIM: The aim was to test whether the ethanolic extract of Fumaria indica (FI) possesses anti-inflammatory and analgesic activities, and fumaric acid (FA) could be one of its bioactive constituent involved in such activities of the extract. MATERIALS AND METHODS: For anti-inflammatory activity, carrageenan-induced edema and cotton pellet induced granuloma tests in rats and for analgesic activity rat tail flick test and hot plate and acetic acid writhing tests in mice were used. All tests were performed after seven daily oral doses of the FI extract (100, 200, and 400 mg/kg/day) and pure FA (1.25, 2.50, and 5.00 mg/kg/day). RESULTS: Anti-inflammatory activities of FI and FA were observed in carrageenan-induced edema and cotton pallet granuloma even after their lowest tested doses. No analgesic activity of lowest tested dose of FA was observed in the acetic acid writhing test, but likewise, all tested dose levels of FI, higher tested dose levels of FA were also possess significant analgesic activity in this test. Further, significant analgesic activities of both FI and FA in hot plate and tale flick tests were observed after all their tested doses. CONCLUSIONS: These observations are in agreement with our working hypothesis on the connection of FA in mode(s) of action(s) of FI, and reaffirm the conviction that FI could be an herbal alternative against fibromyalgia and other pathologies often associate with, or caused by, inflammatory processes.

Beneficial effects of Brassica juncea on cognitive functions in rats.

UNLABELLED: CONTEXT. Brassica juncea (BJ; Linnaeus) Czern & Coss (Brassicaceae), commonly known as Indian mustard, are enriched in redox-active polyphenols with antidiabetic activities. Diverse other health benefits of this edible plant have been described in classical Ayurvedic texts. OBJECTIVE: The reported experiments were designed to assess therapeutic potential of a methanol extract of BJ leaves for treatment of cognitive disorders associated with diabetes or caused by central cholinergic dysfunctions. MATERIALS AND METHODS: Elevated plus-maze and active- and passive-avoidance tests were used to assess anti-amnesic potentials of BJ (100, 200 and 400 mg/kg/day, p.o., for 10 days) in alloxan diabetic or scopolamine-challenged rats. Treatment effects on brain acetylcholinesterase (AChE), superoxide dismutase (SOD) and catalase (CAT) activities were quantified in behavioral tested animals. RESULTS: Anti-amnesic efficacy of all three tested BJ doses against scopolamine-induced amnesia was almost equal in all behavioral tests. Such efficacy of the extract in diabetic rats was increased always with its increasing doses. All treatments of BJ dose dependently decreased the elevated level of AChE, and significantly increased the SOD and CAT levels in brain homogenates of scopolamine-challenged and diabetic rats. Minimal effective oral daily doses of BJ in all tests were 100 mg/kg/day for 10 consecutive days. DISCUSSION AND CONCLUSION: Our observation indicates that BJ could be a therapeutic option for treatment of cognitive disorders associated with diabetes, or caused by cholinergic deficit and brain oxidative status. They also indicate that the bioactive constituents or mode of actions involved in observed effects of the extract in scopolamine-challenged or diabetic rats are most probably not the same.

Effects of ethanolic extract of Fumaria indica L. on rat cognitive dysfunctions.

Fumaria indica L. in Ayurveda is known as Parpat and traditionally used to calm the brain. Due to lack of scientific validation, 50% ethanolic extract of F. indica L. (FI) was evaluated for putative cognitive function modulating effects. Suspension of FI in 0.3% carboxymethyl cellulose (CMC) was orally administered to rats during the entire experimental period of 16 days at dose levels of 100, 200, and 400 mg/kg/day. Piracetam was used as standard nootropic. Behavioral models of learning and memory used were modified elevated plus-maze (M-EPM) and passive avoidance (PA) tests. Scopolamine (I mg/kg, s.c.), sodium nitrite (25 mg/kg, i.p.), and electroconvulsive shock (150 mA, 0.2 sec) were used to induce amnesia. Acetylcholinesterase (AChE) activity, muscarinic receptor density, oxidative status, and cytokine expressions [tumor necrosis factor alpha (TNF-α), interleukin (IL)-1ß, and IL-10] were also assessed. Piracetam (500 mg/kg/day)-like memory-enhancing and anti-amnesic activity of the extract was observed. FI showed dose-dependent decrease in brain AChE activity and increase in muscarinic receptor density, and such was also the case for its observed beneficial effects on the brain antioxidative status. FI also inhibited the scopolamine-induced overexpression of the three tested cytokines observed in rat's brain. FI possesses nootropic-like beneficial effects on cognitive functions.

Beneficial effect of Hypericum perforatum on depression and anxiety in a type 2 diabetic rat model.

Recent studies have revealed diverse therapeutically interesting pharmacological properties of a standardized Hypericum perforatum extract (HpE) potentially useful for treatments of patients with metabolic and psychiatric disorders. Consequently, the presented experiments were designed to test usefulness of the extract for the treatment of comorbid conditions of mood disturbances and anxiety in diabetic rats. Type 2 diabetes mellitus was induced in overnight fasted rats by a single i.p. injection of streptozotocin (STZ; 65 mg/kg), 15 min after an i.p. injection of nicotinamide (120 mg/kg). HpE was administered orally (100 and 200 mg/kg b.w..) to diabetic animals for 14 days. Anxiolytic activity was evaluated using open-field exploration test (OFT) and elevated plus maze (EPM) test. Antidepressant activity was assessed using Porsolt's forced swim test (FST). Fasting blood glucose levels in different groups were analyzed on the 14th day. Diabetic rats showed significant increase in anxiety in OFT and EPM compared to non diabetic normal control rats. Diabetic rats treated with HpE have shown significant anxiolytic activity in OFT and EPM test. In FST, immobility period of vehicle treated diabetic rats was significantly increased (p < 0.05) compared to normal control rats. Treatment with HpE significantly decreased (p < 0.001) immobility period compared to vehicle treated diabetic control rats. HpE treatment significantly reduced elevated blood glucose levels in diabetic rats. The presented observations strongly suggest that HpE could be suitable alternative therapeutic option for prevention, as well as treatment, of comorbidities caused by, or associated with, depression, anxiety and diabetes.

Hypolipidemic and Antiobesity-Like Activity of Standardised Extract of Hypericum perforatum L. in Rats.

Hypericum perforatum is known to have diverse medicinal uses for centuries. The antidepressant activity of Hypericum perforatum is widely accepted and proved in both animal and clinical studies. Present study was undertaken to investigate the effect of Hypericum perforatum in a battery of animal models for metabolic disorder. Hypericum is tested for hypolipidemic activity in normal rats, antiobesity activity in high-fat-diet induced obese rats, and fructose-fed rats. Hypericum was orally administered as suspension in 0.3% carboxymethyl cellulose at the doses of 100 and 200 mg/kg body weight for 15 consecutive days. Hypericum significantly lowered total cholesterol and low-density cholesterol in normal rats. Hypericum significantly inhibited weight gain in high-fat-fed rats. In fructose-fed rats, Hypericum normalised the dyslipidemia induced by fructose feeding and improved the insulin sensitivity. Taken together, Hypericum could be the antidepressant therapy of choice for patients suffering from comorbid diabetes and obesity.

Stimulation of hippocampal acetylcholine release by hyperforin, a constituent of St. John's Wort.

Extracts of the medicinal plant St. John's Wort (Hypericum perforatum) are widely used in the therapy of affective disorders and have been reported to exert antidepressant, anxiolytic, and cognitive effects in experimental and clinical studies. We here report that hyperforin, the major active constituent of the extract, increases the release of acetylcholine from rat hippocampus in vivo as determined by microdialysis. Hippocampal acetylcholine levels were increased by 50-100% following the systemic administration of pure hyperforin at doses of 1 and 10 mg/kg. The effect was almost completely suppressed by local perfusion with calcium-free buffer or with tetrodotoxin (1 microM). We conclude that hyperforin releases hippocampal acetylcholine by an indirect mechanism of action which is calcium-dependent and requires intact neuronal communication and cell firing. Our findings suggest therapeutic efficacy of St. John's Wort extracts in central cholinergic dysfunction.