Avoidance Test In Mice Research Articles

The Influence of an Acute Administration of Cannabidiol or Rivastigmine, Alone and in Combination, on Scopolamine-Provoked Memory Impairment in the Passive Avoidance Test in Mice.

Memory is one of the most important abilities of our brain. The process of memory and learning is necessary for the proper existence of humans in the surrounding environment. However, sometimes there are unfavourable changes in the functioning of the brain and memory deficits occur, which may be associated with various diseases. Disturbances in the cholinergic system lead to abnormalities in memory functioning and are an essential part of clinical symptoms of many neurodegenerative diseases. However, their treatment is difficult and still unsatisfactory; thus, it is necessary to search for new drugs and their targets, being an alternative method of mono- or polypharmacotherapy. One of the possible strategies for the modulation of memory-related cognitive disorders is connected with the endocannabinoid system (ECS). The aim of the present study was to determine for the first time the effect of administration of natural cannabinoid compound (cannabidiol, CBD) and rivastigmine alone and in combination on the memory disorders connected with cholinergic dysfunctions in mice, provoked by using an antagonist of muscarinic cholinergic receptor-scopolamine. To assess and understand the memory-related effects in animals, we used the passive avoidance (PA) test, commonly used to examine the different stages of memory. An acute administration of CBD (1 mg/kg) or rivastigmine (0.5 mg/kg) significantly affected changes in scopolamine-induced disturbances in three different memory stages (acquisition, consolidation, and retrieval). Interestingly, co-administration of CBD (1 mg/kg) and rivastigmine (0.5 mg/kg) also attenuated memory impairment provoked by scopolamine (1 mg/kg) injection in the PA test in mice, but at a much greater extent than administered alone. The combination therapy of these two compounds, CBD and rivastigmine, appears to be more beneficial than substances administered alone in reducing scopolamine-induced cognitive impairment. This polytherapy seems to be favourable in the pharmacotherapy of various cognitive disorders, especially those in which cholinergic pathways are implicated.

Binge-like mephedrone treatment induces memory impairment concomitant with brain kynurenic acid reduction in mice

While mephedrone (4-methylmethcathinone), a synthetic cathinone derivative, is widely abused by adolescents and young adults, the knowledge about its long-term effects on memory processes is limited. Kynurenic acid (KYNA) is a neuroactive metabolite of the kynurenine pathway of tryptophan degradation. KYNA is considered an important endogenous modulator influencing physiological and pathological processes, including learning and memory processes. The aim of this study was to determine whether (A) binge-like mephedrone administration (10.0 and 30.0 mg/kg, intraperitoneally, in 4 doses separated by 2 h) induces memory impairments, assessed 2, 8 and 15 days after mephedrone cessation in the passive avoidance test in mice, and whether (B) KYNA is involved in these memory processes. To clarify the role of KYNA in the mephedrone effects, its production in the murine brain in vivo, and in cortical slices in vitro, as well as the activities of kynurenine aminotransferases (KATs) I and II were assessed. Furthermore, cell line experiments were conducted to investigate the effects of mephedrone on normal human brain cells. Our results showed memory impairments 8 and 15 days after binge-like mephedrone administration. At the same time, reduction in the KYNA level in the murine brain was noted. In vitro studies showed no effect of mephedrone on the production of KYNA in cortical slices or on the activity of the KAT I and II enzymes. Finally, exposure of normal cells to mephedrone in vitro resulted in a modest reduction of cell viability and proliferation.

Memory Enhancement with Kynurenic Acid and Its Mechanisms in Neurotransmission.

Kynurenic acid (KYNA) is an endogenous tryptophan (Trp) metabolite known to possess neuroprotective property. KYNA plays critical roles in nociception, neurodegeneration, and neuroinflammation. A lower level of KYNA is observed in patients with neurodegenerative diseases such as Alzheimer’s and Parkinson’s diseases or psychiatric disorders such as depression and autism spectrum disorders, whereas a higher level of KYNA is associated with the pathogenesis of schizophrenia. Little is known about the optimal concentration for neuroprotection and the threshold for neurotoxicity. In this study the effects of KYNA on memory functions were investigated by passive avoidance test in mice. Six different doses of KYNA were administered intracerebroventricularly to previously trained CFLP mice and they were observed for 24 h. High doses of KYNA (i.e., 20–40 μg/2 μL) significantly decreased the avoidance latency, whereas a low dose of KYNA (0.5 μg/2 μL) significantly elevated it compared with controls, suggesting that the low dose of KYNA enhanced memory function. Furthermore, six different receptor blockers were applied to reveal the mechanisms underlying the memory enhancement induced by KYNA. The series of tests revealed the possible involvement of the serotonergic, dopaminergic, α and β adrenergic, and opiate systems in the nootropic effect. This study confirmed that a low dose of KYNA improved a memory component of cognitive domain, which was mediated by, at least in part, four systems of neurotransmission in an animal model of learning and memory.

Cannabidiol Attenuates MK-801-Induced Cognitive Symptoms of Schizophrenia in the Passive Avoidance Test in Mice.

Schizophrenia is a chronic mental disorder that disturbs feelings and behavior. The symptoms of schizophrenia fall into three categories: positive, negative, and cognitive. Cognitive symptoms are characterized by memory loss or attentional deficits, and are especially difficult to treat. Thus, there is intense research into the development of new treatments for schizophrenia-related responses. One of the possible strategies is connected with cannabidiol (CBD), a cannabinoid compound. This research focuses on the role of CBD in different stages of memory (acquisition, consolidation, retrieval) connected with fear conditioning in the passive avoidance (PA) learning task in mice, as well as in the memory impairment typical of cognitive symptoms of schizophrenia. Memory impairment was provoked by an acute injection of the N-methyl-D-aspartate (NMDA) receptor antagonist MK-801 (animal model of schizophrenia). Our results revealed that an acute injection of CBD (30 mg/kg; intraperitoneally (i.p.) improved all phases of long-term fear memory in the PA test in mice. Moreover, the acute injection of non-effective doses of CBD (1 or 5 mg/kg; i.p.) attenuated the memory impairment provoked by MK-801 (0.6 mg/kg; i.p.) in the consolidation and retrieval stages of fear memory, but not in the acquisition of memory. The present findings confirm that CBD has a positive influence on memory and learning processes in mice, and reveals that this cannabinoid compound is able to attenuate memory impairment connected with hypofunction of glutamate transmission in a murine model of schizophrenia.

CB1 receptors in the formation of the different phases of memory-related processes in the inhibitory avoidance test in mice

The endocannabinoid system, through the cannabinoid type 1 (CB1) and 2 (CB2) receptors modulates many physiological functions, including different aspects of memory-related processes.The aim of the present experiments was to explore the role of the endocannabinoid system, through CB1 receptors in the different stages of short-term (acquisition, retention and retrieval) and long-term (acquisition, consolidation and retrieval) memory-related responses, using the inhibitory avoidance (IA) test in mice.Our results revealed that an acute injection of oleamide (10 and 20mg/kg), a CB1 receptor agonist, impairs the short-term or/and long-term acquisition, retention/consolidation, retrieval memory and learning processes in the IA test in mice. In turn, in this test an acute injection of AM 251 (1 and 3mg/kg), a CB1 receptor antagonist, improves the short-term or/and long-term memory stages, described above. Moreover, this memory impairment induced by effective dose of oleamide (20mg/kg) is reversed by non-effective dose of AM 251 (0.25mg/kg) in the IA task, which proves the selectivity of oleamide to CB1 receptors and confirms that the CB1 receptor-related mechanism is one of the possible mechanisms, responsible for memory and learning responses.Obtained results provide clear evidence that the endocannabinoid system, through CB1 receptors, participates in the different stages of short- and long-term memory-related behavior. This knowledge may open in the future new possibilities for the development of CB-based therapies, especially for memory impairment human disorders.

Preventive Effect of Baicalein on Methamphetamine-Induced Amnesia in the Passive Avoidance Test in Mice

Background/Aims: Methamphetamine abuse may produce cognitive impairment. Baicalein, a bioactive flavonoid, has antioxidative, anti-inflammatory and neuroprotective effects. This study examined the effects of baicalein pretreatment on memory performance in the passive avoidance test after either one dose or an acute binge of methamphetamine in Institute of Cancer Research (ICR) mice. Methods: Methamphetamine was administered by intraperitoneal (i.p.) injection of either one dose (3 mg/kg) or an acute binge (3 mg/kg, 4 i.p. injections at 2-hour intervals). The effects of baicalein pretreatment (1 mg/kg, i.p.) on methamphetamine-induced changes of locomotor activity and memory performance were compared with those of eticlopride, a selective dopamine D₂ receptor antagonist. The effects of baicalein on acute binge methamphetamine-induced oxidative stress (malondialdehyde- and nitrotyrosine-modified protein production) in the mouse hippocampus were also examined. Results: One-dose methamphetamine treatment (i.p., 30 min before or immediately after the training trial) induced hyperlocomotion and amnesia in mice, which were blocked by eticlopride but not by baicalein pretreatment. The memory performance in mice was impaired 5 days after acute binge methamphetamine, which was significantly attenuated by baicalein but not by eticlopride pretreatment. Baicalein pretreatment also attenuated acute binge methamphetamine-induced oxidative stress in the mouse hippocampus. Conclusions: Baicalein exhibits antioxidative and neuroprotective effects in attenuating acute binge methamphetamine-induced memory deficits and oxidative hippocampal damage.

Effects of Agents Influencing Serotonergic and Cannabinoid Systems on Memory in the Avoidance Test in Mice

Adult male albino mice in a shuttle box system were used for examination of learning for avoidance behavior and its deactivation. We measured the step-through latency in the acquisition of the task (STLa) before injections of the drugs tested (fluoxetine and URB597, a serotonin reuptake inhibitor, SSRI, and an agent preventing decomposition of endocannabinoids, respectively) and the respective latency 24 h after injections of these agents (STLr); total time spent in the dark compartment (TDC) was also measured in these situations. In mice that received fluoxetine (5, 10, and 20 mg/kg), the STLr were longer than those in the control, and the difference was significant at 10 mg/kg. Injections of URB597 decreased the STLr, and at medium and high doses (0.3 and 1.0 mg/kg) significant differences were observed. All doses of fluoxetine led to significant decreases in the TDC values, while injections of URB597 increased this index (at 0.3 and 1.0 mg/kg, the shifts were significant). Combined injections of fluoxetine and URB597 (5 + 0.1, 10 + 0.3, and 20 + 1.0 mg/kg) increased the STLr values and decreased TDC values to levels comparable with those at isolated injections of fluoxetine in the respective doses. Thus, fluoxetine improves memory, while URB597 impaired it; fluoxetine is capable of nullifying the negative effects of URB597.

A DKP cyclo(L-Phe-L-Phe) found in chicken essence is a dual inhibitor of the serotonin transporter and acetylcholinesterase.

Diketopiperazines (DKPs) are naturally-occurring cyclic dipeptides with a small structure and are found in many organisms and in large amounts in some foods and beverages. We found that a chicken essence beverage, which is popular among Southeast Asians as a traditional remedy and a rich source of DKPs, inhibited the serotonin transporter (SERT) and suppressed serotonin uptake from rat brain synaptosomes, which prompted us to isolate and identify the active substance(s). We purified a SERT inhibitor from the chicken essence beverage and identified it as the DKP cyclo(L-Phe-L-Phe). Interestingly, it was a naturally occurring dual inhibitor that inhibited both SERT and acetylcholinesterase (AChE) in vitro. The DKP increased extracellular levels of the cerebral monoamines serotonin, norepinephrine, and dopamine in the medial prefrontal cortex and acetylcholine in the ventral hippocampus of freely moving rats when administered orally. Moreover, cyclo(L-Phe-L-Phe) significantly shortened escape latency in the water maze test in depressed mice previously subjected to a repeated open-space swimming task, which induces a depression-like state. Cyclo(L-Phe-L-Phe) also significantly improved accuracy rates in a radial maze test in rats and increased step-through latencies in a passive avoidance test in mice with scopolamine-induced amnesia. These animal test results suggest that cyclo(L-Phe-L-Phe), which is present abundantly in some foods such as chicken essence, may abrogate the onset of depression and, thus, contribute to preventing the development of Alzheimer’s disease and other dementia, because senile depression is a risk factor for dementia.

Synthesis and biological evaluation of Schiff’s bases and 2-azetidinones of isonocotinyl hydrazone as potential antidepressant and nootropic agents

The synthesis and pharmacological activity of N′-[(1Z)-(substituted aromatic) methylidene] pyridine-4-carbohydrazides (3a–k) and N-[3-chloro-2-(substituted aromatic)-4-oxoazetidin-1-yl]pyridine-4-carboxamides (5a–k) are described. Synthesis of 2-azetidinones was performed by novel methods of stirring and sonication involving the cyclocondensation of the appropriate Schiff’s bases (3a–k) with chloroacetyl chloride, followed by the addition of triethyl amine in the presence of molecular sieves. The compounds were investigated for their antidepressant activity, compounds N′-[(1Z)-(2,5-dimethoxyphenyl)methylidene]pyridine-4-carbohydrazide (3k) and N-[3-chloro-2-(2,5-dimethoxyphenyl)-4-oxoazetidin-1-yl]pyridine-4-carboxamide (5k) with 2,5-dimethoxy substitution on the aryl ring exhibited the highest antidepressant activity. In the elevated plus maze test and passive avoidance test in mice for the evaluation of nootropic activity N′-[(1Z)-(4-nitrophenyl)methylidene]pyridine-4-carbohydrazide (3d) and N-[3-chloro-2-(4-nitrophenyl)-4-oxoazetidin-1-yl]pyridine-4-carboxamide (5d) with para nitro substitution on the aryl ring exhibited the highest activity. All synthesised Schiff’s bases and azetidinone analogues exhibited antidepressant and nootropic activities in a dose dependant manner. The results confirmed the fact that the 2-azetidinone skeleton has potential as a CNS active agent and can be explored for the development of more potent and safe CNS active agents for therapeutic use.

Synthesis and Nootropic Activity of Some 2,3‐Dihydro‐1H‐isoindol‐1‐one Derivatives Structurally Related with Piracetam

Three 2,3-dihydro-1H-isoindol-1-ones structurally related with piracetam (=2-oxopyrrolidine-1-acetamide) have been synthesized and tested for their nootropic effects in the passive avoidance test in mice. Compounds (RS)-2, (R,R)-3, and (R,S)-3 were obtained in good yields in only two steps starting from methyl DL-phthaloylalanine. Compound (RS)-2 exhibited nootropic activity at lower doses than piracetam, used as reference drug, but it showed lower efficacy. Whereas diastereoisomers (R,R)-3 and (R,S)-3 were as potent as piracetam to revert amnesia induced by scopolamine, (R,S)-3 showed lower efficacy than (R,R)-3. Only (R,R)-3 showed myorelaxant effect at doses of 10 and 30 mg/kg; other compounds did not exhibit any anticonvulsant, sedative, myorelaxant, or impaired motor-coordination effect in mice. These synthesized 2,3-dihydro-1H-isoindol-1-one derivatives constitute a new kind of nootropic compounds.

Effects of Uncaria tomentosa total alkaloid and its components on experimental amnesia in mice: elucidation using the passive avoidance test.

The effects of Uncaria tomentosa total alkaloid and its oxindole alkaloid components, uncarine E, uncarine C, mitraphylline, rhynchophylline and isorhynchophylline, on the impairment of retention performance caused by amnesic drugs were investigated using a step-down-type passive avoidance test in mice. In this test, the retention performance of animals treated with the amnesic and test drugs before training was assessed 24 h after training. Uncaria tomentosa total alkaloid (10-20 mg kg(-1), i.p.) and the alkaloid components (10-40 mg kg(-1), i.p.), as well as the muscarinic receptor agonist oxotremorine (0.01 mg kg(-1), i.p.), significantly attenuated the deficit in retention performance induced by the muscarinic receptor antagonist scopolamine (3 mg kg(-1), i.p.). The effective doses of uncarine C and mitraphylline were larger than those of other alkaloid components. Uncarine E (20 mg kg(-1), i.p.) also blocked the impairment of passive avoidance performance caused by the nicotinic receptor antagonist mecamylamine (15 mg kg(-1), i.p.) and the N-methyl-D-aspartate (NMDA) receptor antagonist (+/-)-3-(2-carboxypiperazin-4-yl)-propyl-1-phosphonic acid (CPP; 7.5 mg kg(-1), i.p.), but it failed to affect the deficit caused by the benzodiazepine receptor agonist diazepam (2 mg kg(-1), i.p.). Rhynchophylline significantly reduced the mecamylamine-induced deficit in passive avoidance behaviour, but it failed to attenuate the effects of CPP and diazepam. These results suggest that Uncaria tomentosa total alkaloids exert a beneficial effect on memory impairment induced by the dysfunction of cholinergic systems in the brain and that the effect of the total alkaloids is partly attributed to the oxindole alkaloids tested. Moreover, these findings raised the possibility that the glutamatergic systems are implicated in the anti-amnesic effect of uncarine E.

Extracts of Liriopsis tuber protect AMPA induced brain damage and improve memory with the activation of insulin receptor and ERK I/II

The brain insulin receptor and ERK I/II are known to play an important role in memory formation and neuroprotection. A series of experiments was designed to explore if Liriopsis tuber (LT) extracts could exhibit neuroprotection and memory enhancing actions. LT was extracted with 70% methanol and subsequently fractionated into chloroform (fraction C), chloroform/methanol-(3:1) (fraction CM), methanol-soluble (fraction M) and methanol-insoluble, water-soluble fractions (fraction A). The LT fractions (T, C, M, A) significantly inhibited the cortical depolarization induced by AMPA in cortical slices of rats. In addition, these fractions were also effective in promoting memory in the passive avoidance test in mice. To gain insight into the mechanism of memory enhancing effects by Liriopsis tuber extracts, the activities of hippocampal insulin receptors and ERK I/II were tested in rats. Extract of LT (T) dramatically stimulated tyrosine phosphorylation of the insulin receptor, while fraction C of LT also significantly stimulated the same. In addition, ERK I/II were stimulated and cholinesterase activities were inhibited by fractions T, C, M and A in the rat hippocampus. These results suggest that Liriopsis tuber extracts may exert neuroprotection and memory enhancing effects via activation of the insulin receptor and ERK I/II as well as inhibiting cholinesterase.

β-Lactotensin, a neurotensin agonist peptide derived from bovine β-lactoglobulin, enhances memory consolidation in mice

β-Lactotensin (His-Ile-Arg-Leu) is an ileum-contracting tetrapeptide isolated from bovine β-lactoglobulin. We previously reported that a neurotensin agonist β-lactotensin shows antinociceptive effect through neurotensin NT 2 receptor. We found that centrally or orally administered β-lactotensin at a dose of 60 nmol/mouse or 300–500 mg/kg, respectively, increased memory consolidation in the step-through-type inhibitory avoidance test in mice. The memory-enhancing activity of β-lactotensin was inhibited by the dopamine D 2 receptor antagonist raclopride but not the D 1 receptor antagonist SCH23390. Taken together, β-lactotensin might improve memory consolidation through activating the dopamine D 2 receptor.

Enterostatin (APGPR) enhances memory consolidation in mice

Enterostatin (APGPR) is a pentapeptide released from its precursor protein, procolipase. We found for the first time that enterostatin has memory-enhancing activity. Enterostatin enhanced memory consolidation after central or oral administration at a dose of 10 nmol/mouse or 300 mg/kg, respectively, in a step-through type passive avoidance test in mice. The memory-enhancing activity of enterostatin was inhibited by pretreatment with lorglumide, an antagonist for cholecystokinin 1 (CCK 1) receptor. However, enterostatin had no affinity for CCK receptors. These results suggest that enterostatin improves memory retention through CCK release.

Endocannabinoids and beta-amyloid-induced neurotoxicity in vivo: effect of pharmacological elevation of endocannabinoid levels.

We investigated the involvement of endocannabinoids in the control of neuronal damage and memory retention loss in rodents treated with the beta-amyloid peptide (1-42) (BAP). Twelve days after stereotaxic injection of BAP into the rat cortex, and concomitant with the appearance in the hippocampus of markers of neuronal damage, 2-arachidonoyl glycerol, but not anandamide, levels were enhanced in the hippocampus. VDM-11 (5 mg/kg, i.p.), an inhibitor of endocannabinoid cellular reuptake, significantly enhanced rat hippocampal and mouse brain endocannabinoid levels when administered sub-chronically starting either 3 or 7 days after BAP injection and until the 12-14th day. VDM-11 concomitantly reversed hippocampal damage in rats, and loss of memory retention in the passive avoidance test in mice, but only when administered from the 3rd day after BAP injection. We suggest that early, as opposed to late, pharmacological enhancement of brain endocannabinoid levels might protect against beta-amyloid neurotoxicity and its consequences.

Pharmacological effects of carcinine on histaminergic neurons in the brain.

1 Carcinine (beta-alanyl histamine) is an imidazole dipeptide. The present study was designed to characterize the pharmacological effects of carcinine on histaminergic activity in the brain and on certain neurobehavior. 2 Carcinine was highly selective for the histamine H3 receptor over H1 or H2 receptor (Ki (microM)=0.2939+/-0.2188 vs 3621.2+/-583.9 or 365.3+/-232.8 microM, respectively). 3 Carcinine at a dose of 20 mg kg(-1) slightly increased histidine decarboxylase (HDC) activity in the cortex (from 0.186+/-0.069 to 0.227+/-0.009 pmol mg protein(-1) min(-1)). In addition, carcinine (10, 20, and 50 mg kg(-1)) significantly decreased histamine levels in mice brain. 4 Like thioperamide, a histamine H3 receptor antagonist, carcinine (20, 50 microM) significantly increased 5-HT release from mice cortex slices, but had no apparent effect on dopamine release. 5 Carcinine (20 mg kg(-1)) significantly inhibited pentylenetetrazole-induced kindling. This inhibition was completely reversed by (R)-alpha-methylhistamine, a representative H3 receptor agonist, and alpha-fluromethylhistidine, a selective HDC inhibitor. 6 Carcinine (20 mg kg(-1)) ameliorated the learning deficit induced by scopolamine. This amelioration was reversed by (R)-alpha-methylhistamine as evaluated by the passive avoidance test in mice. 7 Like thioperamide, carcinine dose-dependently increased mice locomotor activity in the open-field test. 8 The results of this study provide first and direct evidence that carcinine, as a novel histamine H3 receptor antagonist, plays an important role in histaminergic neurons activation and might be useful in the treatment of certain diseases, such as epilepsy, and locomotor or cognitive deficit.

Synthesis, biological evaluation, and receptor docking simulations of 2-[(acylamino)ethyl]-1,4-benzodiazepines as kappa-opioid receptor agonists endowed with antinociceptive and antiamnesic activity.

The synthesis and biological evaluation of a series of new derivatives of 2-substituted 5-phenyl-1,4-benzodiazepines, structurally related to tifluadom (5), are reported. Chemical and pharmacological studies on compounds 6 have been pursued with the aim of expanding the SAR data and validating the previously proposed model of interaction of this class of compounds with the kappa-opioid receptor. The synthesis of the previously described compounds 6 has been reinvestigated in order to obtain a more direct synthetic procedure. To study the relationship between the stereochemistry and the receptor binding affinity, compounds 6e and 6k were selected on the basis of their evident structural resemblance to tifluadom. Since a different specificity of action could be expected for the enantiomers of 6e and 6k, owing to the results shown by (S)- and (R)-tifluadom, their racemic mixtures have been resolved by means of liquid chromatography with chiral stationary phases (CSP), and the absolute configuration of the enantiomers has been studied by circular dichroism (CD) and (1)H NMR techniques. Moreover, some new 2-[(acylamino)ethyl]-1,4-benzodiazepine derivatives, 6a-d,f,g,j, have been synthesized, while the whole series (6a-o) has been tested for its potential affinity toward human cloned kappa-opioid receptor. The most impressive result obtained from the binding studies lies in the fact that this series of 2-[2-(acylamino)ethyl]-1,4-benzodiazepine derivatives binds the human cloned kappa-opioid receptor subtype very tightly. Indeed, almost all the ligands within this class show subnanomolar K(i) values, and the least potent compound 6o shows, in any case, an affinity in the nanomolar range. A comparison of the affinities obtained in human cloned kappa-receptor with the correspondent one obtained in native guinea pig kappa-receptor suggests that the human cloned kappa-receptor is less effective in discriminating the substitution pattern than the native guinea pig kappa-receptor. Furthermore, the results obtained are discussed with respect to the interaction with the homology model of the human kappa-opioid receptor, built on the recently solved crystal structure of rhodopsin. Finally, the potential antinociceptive and antiamnesic properties of compounds 6e and 6i have been investigated by means of the hot-plate and passive avoidance test in mice, respectively.

Memory enhancing actions of Asiasari radix extracts via activation of insulin receptor and extracellular signal regulated kinase (ERK) I/II in rat hippocampus

Brain insulin receptor and ERK I/II are suggested to play a role in memory formation. We designed a series of experiments to explore if Asiasari radix (AR) extracts could display memory enhancing actions possibly via the activation of insulin receptor and ERK I/II in mice and rats. Methanol extract of AR had significantly increased survival time in the NaNO 2 intoxication assay in mice. Methanol extract of Asiasari radix (fraction 1) and its subfractions, chloroform-soluble fraction (fraction 2) and chloroform-insoluble, methanol-soluble fraction (fraction 4) were further tested for memory formation. In eight-arm radial maze experiments, both reference memory errors and working memory errors were significantly decreased in mice by fractions 1, 2 and 4. In addition, these fractions were also effective in promoting memory in the passive avoidance test in mice and rats. To gain insight into the mechanism of memory enhancing effects by Asiasari radix extracts, the activities of hippocampal insulin receptors and ERK I/II were tested in mice and rats. Fraction 1 significantly stimulated tyrosine phosphorylation of the insulin receptor, whereas ERK I/II were stimulated by fractions 1, 2 and 4. These fractions also inhibited cholinesterase activities in rats. These results suggest that Asiasari radix extracts may exert memory enhancing effects via activation of insulin receptor and ERK I/II as well as decreasing cholinesterase activity.

Pharmacological activity of Guarana ( Paullinia cupana Mart.) in laboratory animals

Mice that ingested a suspension of guarana ( Paullinia cupana, Sapindaceae) in a dose of 0.3 mg/ml showed a significant increase in physical capacity when subjected to a stressful situation such as forced swimming after 100 and 200 days of treatment. Such an effect, however, was not obtained with a concentration of 3.0 mg/ml, nor with the ingestion of a suspension of ginseng 5.0 mg/ml, nor of a solution of caffeine 0.1 mg/ml. Guarana, both after a single (3.0 and 30 mg/kg) or chronic administrations (0.3 mg/ml), was able to partially reverse the amnesic effect of scopolamine as measured through a passive avoidance test in mice and rats, indicating a positive effect on memory acquisition. However, no effect was observed when an active avoidance task was used in rats, even after 20 days of guarana administration. There was also a tendency of rats treated with 0.3 mg/ml of guarana to better maintain the memory of a Lashley III maze path. The animals had the same average lifespan, indicating a low toxicity of guarana, even after 23 months of treatment.

P-172 - Effect of clobenpropit, a histamine H3-receptor antagonist, on a scopolamine-induced amnesia in the passive avoidance test in mice.

P-172 - Effect of clobenpropit, a histamine H3-receptor antagonist, on a scopolamine-induced amnesia in the passive avoidance test in mice.