Passive Avoidance Response Test Research Articles

Effect of resistance and endurance training with ursolic acid on oxidative stress and cognitive impairment in hippocampal tissue in HFD/STZ-induced aged diabetic rats.

The increase in age-related cognitive impairment (CIs) and diabetes mellitus is a global health concern. Exercise training has been reported to activate the Nrf2/Keap1/ARE signaling and enhance the antioxidant defense pathways in some animal models. This study aimed to investigate the effects of ursolic acid (UA) associated with resistance or endurance training on antioxidant markers, and the Nrf2/Keap1/ARE pathway in the brain of older diabetic rats. 23-month-aged diabetes induced male Wistar rats were randomly assigned to seven groups (n=8). UA supplementation (250 mg/kg, daily) was administered along with resistance (60% maximum capacity of voluntary carrying [MVCC], 14-20 climbs) or endurance training (60-75% velocity at maximal oxygen uptake [vVO2max]), five days/week for eight weeks. Cognitive-motor functioning was assessed through open-field and passive avoidance response tests. Nrf2, Keap1, and antioxidant markers including SOD, CAT, GPx, and GSH were measured in the hippocampus tissue. The results showed positive effect of resistance training (P≤0.001) on Nrf2. There was endurance training with supplementation main effect (P=0.018) on Keap1 concentration. SOD revealed a significant endurance/resistance training by supplementation interaction effect (P≤0.05); however, there was no main training or UA supplementation effects on CAT, GPx, and GSH, despite improving spatial memory changes in exercise or UA groups. It appears that UA treatment with resistance or endurance exercise has some beneficial effects on Nrf2 and some antioxidant markers. However, more research is needed to elucidate UA's interaction effects and exercise interventions in diabetic situations.

Effects of quercetin on the neuromotor function and behavioral responses of Wistar and Zucker rats fed a high-fat and high-carbohydrate diet

Quercetin can affect some pathological manifestations in obesity. The mechanism underlying the presumed therapeutic effect of quercetin is probably related to the influence on the central processes regulating energy homeostasis. Thus, the purpose of this study was to examine the effect of quercetin on the neuromotor and behavioral functions in Zucker (Z) and Wistar (W) rats with genetically and/or diet-induced obesity. Rats of both strains received balanced or high fat and fructose diet (HFCD) in a 62-day experiment or the same diets supplemented with quercetin at the dose of 50 mg/kg body weight per day. The neuromotor function and behavioral responses were examined using the grip strength test, open field test, elevated plus maze test and conditioned passive avoidance response (CPAR) test. The quercetin potentiated a decrease in anxiety in W rats consumed HFCD and this effect was absent in Z rats with a defect in the leptin receptor gene. In contrast, quercetin increased locomotor activity and impaired short-term memory in the CPAR test only in Z rats with the absence of normal leptin reception. Against the background of the identified changes quercetin exerted significant effects on the lipid and nitrogen metabolism indices such as HDL cholesterol, AsAT/AlAT activities ratio, urea level as well as body and fat mass that were different in Z and W rats. The data obtained show that the effects of quercetin on behavior vary significantly between two strains of rat and consequently are mediated by processes of leptin reception.

Study of the Reaction of Hydroxybenzoyl Chlorides and Their Derivatives with Imidazole

The reaction of hydroxybenzoyl chlorides with imidazole was studied on an example of the Schotten-Baumann reaction of salicyloyl and acetylsalicyloyl chlorides with imidazole, which, according to soe published data, can take two different ways. It was shown that the Schotten-Baumann reaction with imidazole involves imidazole ring opening (Bamberger cleavage) to form l,2-bis(salicyloylamino)ethylene and l,2-bis(acetylsalicyloylamino)ethylene rather than N-salicyloylimidazole and N-acetylsalicyloylimidazole. N-Hydroxybenzoylimidazoles were synthesized by the reaction of hydroxybenzoyl chlorides (and derivatives) with a double excess of imidazole in an aprotic solvent (chloroform, benzene, or diethyl ether) at room temperature. The highest yields (about 80%) of N-hydroxybenzoylimidazoles were obtained in chloroform. Some of the newly synthesized compounds were tested for psychotropic (open field and passive avoidance response tests) and analgesic activities (vocalization threshold test). The best results were obtained with N-(2-hydroxybenzoyl)imidazole, which showed an evident analgesic activity, and, therewith, the motor score and oriented exploratory activity parameters were higher than in the control group.

Comparative analysis of the influence of a high-fat/high-carbohydrate diet on the level of anxiety and neuromotor and cognitive functions in Wistar and DAT-KO rats.

We compared anxiety, neuromotor, and cognitive functions in mutant rats with different allelic variants of dopamine transporter DAT knockout receiving balanced or excess in fat and fructose diet. The experiments were performed in DAT−/− homozygotes, DAT+/− heterozygotes, and DAT+/+ wild type rats. The genotype of DAT‐KO rats was confirmed by restriction analysis of DAT gene compared to behavioral responses in the open field test (OF). Animals in the first groups of each strain were fed a balanced AIN93M diet; and those in the second groups with a high‐fat/high‐fructose diet. Neuromotor function was studied as grip strength, and behavioral responses were assessed in the elevated plus maze and conditioned passive avoidance response tests. The mass of the internal organs and white and brown fat, as well as selected lipid and nitrogen metabolism parameters in blood plasma were determined at the end of the experiment. DAT−/− had the highest specific grip strength, and showed an increase in initial exploratory activity in comparison with DAT+/− and DAT +/+. The exploratory activity was significantly reduced in the second test compared to the first one in DAT−/− and DAT+/− of first but not second group. Anxiety decreased with age in the second groups of DAT+/− and DAT+/+ (but not in DAT−/−) and was higher in DAT+/+ than in DAT+/− and DAT−/−. Excess fat and fructose resulted in the deterioration of short‐term memory in DAT+/+. Lipidomic indices of blood plasma were less responsive to diet in DAT−/− and DAT−/+ in comparison to DAT+/+. The increased AsAT/AlAT activity ratio in DAT−/− compared with those in DAT+/+ suggests the activation of catabolism activity in the mutants. The consumption of excess fat and fructose significantly modified the effects produced by DAT gene allelic variants presumably due to the influence on the processes of dopamine metabolism.

Antioxidant hydrolyzed peptides from Manchurian walnut (Juglans mandshurica Maxim.) attenuate scopolamine-induced memory impairment in mice.

Walnut protein, which is obtained as a by-product of oil expression, has not been used efficiently. Although walnuts are beneficial for cognitive functioning, the potential of their protein composition in strengthening learning and memory functions remains unknown. In this study, the inhibition of memory impairment by the Manchurian walnut hydrolyzed peptide (MWHP) was evaluated. Small-molecular-weight MWHP (<3 kDa) achieved the optimal antioxidative activity. Therefore, MWHP (<3 kDa) was subjected to the following mice trials to evaluate its attenuation effect on memory impairment. In the Morris water maze test, MWHP shortened the total path for searching the platform, reduced the escape latency, and increased the dwelling distance and time in the coverage zone. MWHP also prolonged the latency and diminished errors in the passive avoidance response tests. These behavioral tests demonstrated that MWHP could inhibit scopolamine-induced memory impairment. MWHP improved memory by reducing oxidative stress, inhibiting apoptosis, regulating neurotransmitter functions, maintaining hippocampal CA3 pyramidal neurons, and increasing calmodulin-dependent protein kinase II levels in brain tissues. Experimental results proved that MWHP exhibits potential in improving memory and should be used to develop novel functional food. © 2018 Society of Chemical Industry.

Interspecific Differences in Behavioral Responses and Neuromotorics between Laboratory Rodents Receiving Rations with Easily Digested Carbohydrates.

We assessed the effect of intake of easily digested carbohydrates for 133 days on quantitative parameters of neuromotorics and cognitive function in Wistar rats and C57Bl/6J mice. Neuromotorics (muscle tone) was assessed in rats and mice by the forelimb muscle force (grip strength) over 4 months. Anxiety was assessed in the elevated plus-maze test and cognitive function (short-term and long-term memory) was evaluated by conditioned passive avoidance response (CPAR) test over 3 months. The mice, in contrast to rats, receiving the diet with easily digested sugars demonstrated suppression of neuromotorics. Anxiety increased with age in female mice, but not in rats, irrespective of the diet. Cognitive function in rats receiving experimental rations did not change significantly in comparison with the control. In mice, consumption of equimolar mixture of fructose and glucose impared short-term, but not long-term memory, in comparison with the group receiving glucose alone. We revealed a small (by 14-17%), but statistically significant increase in the brain weight in mice receiving fructose and sucrose. The study demonstrates sufficient interspecies differences in the influence of carbohydrate rations on neuromotorics and behavioral responses in the in vivo metabolic syndrome model.

Resveratrol suppressed seizures by attenuating IL-1β, IL1-Ra, IL-6, and TNF-α in the hippocampus and cortex of kindled mice

Objective: There is an urge to identify new molecules which can modulate process of epileptogenesis, since currently available drugs act symptomatically and one-third of the patients remain refractory to the disease. Hence, the present study was conducted to evaluate the effects of Resveratrol (RESV) on epileptogenesis in pentylenetetrazole (PTZ)-induced kindling in mice.Method: Swiss albino mice were administered RESV (10, 20 and 40 mg/kg,p.o) in acute study. On the seventh day animals were subjected to various neurological and neurobehavioral tests viz, Increasing Current Electroshock Test (ICES), PTZ-induced seizures, passive avoidance response, and elevated plus maze test. For the development of kindling PTZ was administered in a dose of 25 mg/kg, i.p. on every alternate day and RESV in all the three doses was administered daily. Seizure score was continuously monitored till the development of kindling and cognition tests were performed in the end of the study. The animals were sacrificed and levels of inflammatory biomarkers viz., IL-1β, interleukin-1 receptor antagonist (IL1-Ra), IL-6, and TNF-α were assessed in the hippocampus and cortex of the kindled animals.Results: RESV in all three doses increased the seizure threshold to hind limb extension in the ICES test. RESV in all the tested doses suppressed the development of kindling and reduced the levels of IL-1β, IL1-Ra, IL-6, and TNF-α in kindled mice.Conclusion: RESV suppressed the development of kindling in mice and decreased the levels of inflammatory biomarkers in their hippocampus. RESV modified brain inflammation during epileptogenesis and found to possess nootropic activity in the kindled mice.

Abstract T P89: Curcumin Encapsulated Stem Cell Exosomes Attenuate Ischemic Brain Injury in Type 1 Diabetic Akita Mice

Background and Purpose: Stroke in type-1 diabetes mellitus (T1DM) is severe in terms of exacerbated brain damage and severe functional decline as compared to non-diabetic stroke. Curcumin possesses remarkable medicinal properties and stem cells exosomes (nano-vesicles; 40-100 nm) have paracrine effects with neovascularization properties. The therapy available for stroke (tissue plasminogen activator) is not effective in diabetic stroke and leads to excessive vasodilation and hemorrhagic transformations. Therefore, we tested the hypothesis that encapsulating curcumin to mouse embryonic stem cell exosomes mitigates type-1 diabetic stroke injury. Methods: We employed 8-10 weeks old male genetic T1DM Ins2+/- Akita mice. Ischemia was performed for 40 min and reperfusion for 7 days in the following mice groups: 1) Sham Akita , 2) Sham Akita + cur-exo , 3) IR Akita , 4) IR Akita + cur-exo . Exosomes were isolated from mouse embryonic stem cells culture conditioned media and encapsulated with curcumin ( cur-exo ). Therapeutic exo-cur units were used for mice treatment intranasally for 7 days. Brain cryo-sections were analyzed for vascular (VCAM, VE-cadherin), glial (GFAP), neuronal (Tuj1, nNOS) coupling in ipsilateral area. Neuronal loss, neurodegeneration was analyzed with NeuN, fluorojade-C staining. White matter damage was examined with luxol fast blue. Intra-carotid FITC-BSA infusion was used to assess venular leakage. Passive avoidance and auditory brainstem response tests were used to determine cognitive functions. Results: Treatment with cur-exo alleviated Infarct volume, edema, and vascular damage in IR Akita + cur-exo mice as compared to IR Akita mice. The axonal-glia damage and venular permeability were exacerbated in IR Akita mice, as compared to sham Akita , which were mitigated after cur-exo treatment. Cur-exo also ameliorated neurodegeneration and promoted neuronal survival as determined through immunolocalization studies. Further, cur-exo remarkably restored cognitive functions (p&lt;0.001, n=6). Conclusion: Our results suggested that combining the therapeutic efficacy of curcumin and stem cells exosomes represent a novel treatment for stroke during T1DM. Acknowledgement: This work was supported by NIH grant HL107640.

An Experimental Study to Evaluate the Effect of Memantine in Animal Models of Anxiety in Swiss Albino Mice.

Due to the adverse effects produced by the present conventional medicines for anxiety disorders, research for newer drugs is still desirable. From the literature it is evident that NMDA receptors play a key role in animal models of anxiety. The present study is done to evaluate the antianxiety effect of memantine in swiss albino mice. The experimental study was conducted from November 2014 to January 2015. Animals were divided into four groups. Twelve mice were randomly allotted in each group. Animals in the first group received normal saline as a control 10ml/kg, lorazepam 0.5mg/kg was administered to second group, memantine 3mg/kg as a test drug was given to the third group and memantine 3mg/kg + lorazepam 0.5mg/kg was administered to the fourth group. All the drugs were given for 7 consecutive days by intraperitoneal route. Results were analyzed by one-way ANOVA followed by Post-hoc Tukey's test. On the 1(st) day, memantine treated group did not show statistical significant anxiolytic effect in both the behavioural paradigms when compared to control group. On the 8(th) day, the animals showed significant decrease p<0.001 in step down latency period in shock free zone (185.4±3.87 Vs 278.3±5.49), significant increase p<0.001 in step down errors (6.8±0.78 Vs 1.4±0.19) and significant increase p<0.001 in total time spent in shock zone (32.1±2.22 Vs 5.6±0.6). In open field test, on 8(th) day the animals treated with memantine when compared to control group, showed significant increase p<0.001 in number of squares crossed (112.7± 2.69 Vs 83.2±2.96), time spent in central square (11.5±1.26 Vs 3.4±0.65), no. of rearings (32.4±2.61 Vs 17±1.81) and significant decrease p<0.001 in freezing time (15.2±1.12 Vs 20.2±2.29). Memantine showed synergistic antianxiety effect when combined with lorazepam. Memantine showed significant anxiolytic effect in open field and passive avoidance response tests which are commonly used experimental models to assess anxiety states in animals.

Neurobehavioral changes in response to alterations in gene expression profiles in the brains of mice exposed to low and high levels of mercury vapor during postnatal development

This study examined the relationship between neurobehavioral changes and alterations in gene expression profiles in the brains of mice exposed to different levels of Hg(0) during postnatal development. Neonatal mice were repeatedly exposed to mercury vapor (Hg(0)) at a concentration of 0.057 mg/m(3) (low level), which was close to the current threshold value (TLV), and 0.197 mg/m(3) (high level) for 24 hr until the 20(th) day postpartum. Behavioral responses were evaluated based on changes in locomotor activity in the open field test (OPF), learning ability in the passive avoidance response test (PA), and spatial learning ability in the Morris water maze (MM) at 12 weeks of age. No significant differences were observed in the three behavioral measurements between mice exposed to the low level of Hg(0) and control mice. On the other hand, total locomotive activity in mice exposed to the high level of Hg(0) was significantly decreased and central locomotion was reduced in the OPF task. Mercury concentrations were approximately 0.4 μg/g and 1.9 μg/g in the brains of mice exposed to the low and high levels of Hg(0), respectively. Genomic analysis revealed that the expression of 2 genes was up-regulated and 18 genes was down-regulated in the low-level exposure group, while the expression of 3 genes was up-regulated and 70 genes was down-regulated in the high-level exposure group. Similar alterations in the expression of seven genes, six down-regulated genes and one up-regulated gene, were observed in both groups. The results indicate that an increase in the number of altered genes in the brain may be involved in the emergence of neurobehavioral effects, which may be associated with the concentration of mercury in the brain. Moreover, some of the commonly altered genes following exposure to both concentrations of Hg(0) with and without neurobehavioral effects may be candidates as sensitive biomarker genes for assessing behavioral effects in the early stages of development.

Mildronate enhances learning/memory and changes hippocampal protein expression in trained rats

Previously we demonstrated that mildronate [3-(2,2,2-trimethylhydrazinium) propionate dihydrate], a representative of the aza-butyrobetaine class of compounds, protects mitochondrial metabolism under conditions such as ischemia. Mildronate also acted as a neuroprotective agent in an azidothymidine-induced mouse model of neurotoxicity, as well as in a rat model of Parkinson's disease. These observations suggest that mildronate may stimulate processes involved in cell survival and change expression of proteins involved in neurogenic processes. The present study investigated the influence of mildronate on learning and memory in the passive avoidance response (PAR) test and the active conditioned avoidance response (CAR) test in rats. The CAR test employed also bromodeoxyuridine (BrdU)-treated animals. Hippocampal cell BrdU incorporation was then immunohistochemically assessed in BrdU-treated, CAR-trained rats to identify proliferating cells. In addition, the expression of hippocampal proteins which could serve as memory enhancement biomarkers was evaluated and compared to non-trained animals' data. These biomarkers included glutamic acid decarboxylase 65/67 (GAD65/67), acetylcholine esterase (AChE), growth-associated protein-43 (GAP-43) and the transcription factor c-jun/activator protein-1 (AP-1). The results showed that mildronate enhanced learning/memory formation that coincided with the proliferation of neural progenitor cells, changing/regulating of the expression of biomarker proteins which are involved in the activation of glutamatergic and cholinergic pathways, transcription factors and adhesion molecule.The data from our study suggest that mildronate may be useful as a possible cognitive enhancer for the treatment of patients with neurodegenerative diseases with dementia.

Investigation into Stereoselective Pharmacological Activity of Phenotropil

Phenotropil [N-carbamoylmethyl-4-aryl-2-pyrrolidone (2-(2-oxo-4-phenyl-pyrrolidin-1-yl) acetamide; carphedon)] is clinically used in its racemic form as a nootropic drug that improves physical condition and cognition. The aim of this study was to compare the stereoselective pharmacological activity of R- and S-enantiomers of phenotropil in different behavioural tests. Racemic phenotropil and its enantiomers were tested for locomotor, antidepressant and memory-improving activity and influence on the central nervous system (CNS) using general pharmacological tests in mice. After a single administration, the amount of compound in brain tissue extracts was determined using an ultra performance liquid chromatography-tandem mass spectrometry (UPLC/MS/MS) method in a positive ion electrospray mode. In the open-field test, a significant increase in locomotor activity was observed after a single administration of R-phenotropil at doses of 10 and 50 mg/kg and S-phenotropil at a dose of 50 mg/kg. In the forced swim test, R-phenotropil induced an antidepressant effect at doses of 100 and 50 mg/kg, and S-phenotropil was active at a dose of 100 mg/kg. R-phenotropil significantly enhanced memory function in a passive avoidance response test at a dose of 1 mg/kg; the S-enantiomer did not show any activity in this test. However, the concentrations of R- and S-phenotropils in brain tissue were similar. In conclusion, the antidepressant and increased locomotor activity relies on both R- and S-phenotropils, but the memory-improving activity is only characteristic of R-phenotropil. These results may be important for the clinical use of optically pure isomers of phenotropil.

Effect of lamotrigine, oxcarbazepine and topiramate on cognitive functions and oxidative stress in PTZ-kindled mice

Cognitive impairment is frequently observed in epileptic patients. It has been seen that not only epilepsy but antiepileptic drugs also impair cognitive functions. The present study was undertaken to assess the effect of three anticonvulsants viz. lamotrigine (5 mg/kg, p.o.), oxcarbazepine (15 mg/kg, p.o.) and topiramate (10 mg/kg, p.o.) on cognitive function and oxidative stress during pentylenetetrazole (PTZ)-kindling in mice. Kindling was induced by the administration of PTZ (25 mg/kg, i.p.) on every alternate day till 5 weeks. Cognition was assessed after the development of kindling. Elevated plus maze (EPM) and passive avoidance response (PAR) tests were carried out after 24 h and 48 h of the last PTZ administration. After completion of behavioural tests malondialdehyde (MDA), glutathione levels, superoxide dismutase and catalase activity were measured as an indicator of oxidative stress. The results of the present study indicate that topiramate (10 mg/kg) administration to kindled animals increased transfer latency and decreased step-down latency in EPM and PAR tests, respectively. However, lamotrigine and oxcarbazepine did not alter the two parameters. Topiramate administration to kindled as well as non-kindled animals has shown increase in MDA and decrease in glutathione levels. Lamotrigine and oxcarbazepine did not show significant alteration in oxidative stress parameters. To conclude, long term administration of topiramate impairs cognitive functions during experimental epilepsy while lamotrigine and oxcarbazepine are safer.

Neurobehavioral effects of combined prenatal exposure to low-level mercury vapor and methylmercury

We evaluated the effects of prenatal exposure to low-level mercury (Hg(0)) or methylmercury (MeHg) as well as combined exposure (Hg(0) + MeHg exposure) on the neurobehavioral function of mice. The Hg(0) exposure group was exposed to Hg(0) at a mean concentration of 0.030 mg/m(3) for 6 hr/day during gestation period. The MeHg exposure was supplied with food containing 5 ppm of MeHg from gestational day 1 to postnatal day 10. The combined exposure group was exposed to both Hg(0) vapor and MeHg according to above described procedure. After delivery, when their offspring reached the age of 8 weeks, behavioral analysis was performed. Open field (OPF) tests of the offspring showed an increase and decrease in voluntary activity in male and female mice, respectively, in the MeHg exposure group. In addition, the rate of central entries was significantly higher in this group than in the control group. The results of OPF tests in the Hg(0) + MeHg exposure group were similar to those in the MeHg exposure group in both males and females. The results in the Hg(0) exposure group did not significantly differ from those in the control group in males or females. Passive avoidance response (PA) tests revealed no significant differences in avoidance latency in the retention trial between the Hg(0), MeHg, or Hg(0) + MeHg exposure group and the control group in males or females. Morris water maze tests showed a delay in the latency to reach the platform in the MeHg and Hg(0) + MeHg exposure groups compared with the control group in males but no significant differences between the Hg(0), MeHg, or Hg(0) + MeHg exposure group and the control group in females. The results of OPF tests revealed only slight effects of prenatal low-level Hg(0) exposure (0.03 mg/m(3)), close to the no-observable-effect level (NOEL) stated by the WHO (0.025 mg/m(3)), on the subsequent neurobehavioral function. However, prenatal exposure to 5 ppm of MeHg affected exploratory activity in the OPF test, and, in particular, male mice were highly sensitive to MeHg. The MeHg and Hg(0) + MeHg exposure groups showed similar neurobehavioral effects. Concerning the effects of prenatal mercury exposure under the conditions of this study, the effects of MeHg exposure may be more marked than those of Hg(0) exposure.

Improvement of pentylenetetrazol-induced learning deficits by valproic acid in the adult zebrafish

Pentylenetetrazol (PTZ) has been shown to induce seizure-like behavior, learning deficits in passive avoidance response test, and an increase in hsp70 (heat shock protein 70) mRNA expression in the adult zebrafish; PTZ has been increasingly appreciated as an excellent model system for the study of seizures. In this study, we demonstrate that valproic acid (VPA), an antiepileptic drug, suppresses seizure-like behavior and improves learning ability in adult zebrafish treated with PTZ. Pretreatment with VPA significantly reduces rapid involuntary movement and abrupt changes in moving direction in the PTZ-treated zebrafish. PTZ-induced learning impairments were also improved in the zebrafish pretreated with 200 or 500 μM VPA. However, the scopolamine-induced impairments of learning ability were not improved by VPA pretreatment. It is worth noting that while the zebrafish treated with 500 μM VPA for 1–3 weeks learned the passive avoidance response, those treated with 1 or 2 mM VPA for 3 h didn't. Furthermore, the increased level of hsp70 expression induced by PTZ, a stress marker protein, was significantly reduced in the VPA-pretreated zebrafish brains. Collectively, our data show the antiepileptic effects of VPA in the adult zebrafish, which coincides with reduced hsp70 mRNA expression, rescued learning impairment under PTZ-treated conditions.

Scopolamine-induced learning impairment reversed by physostigmine in zebrafish

In this study, the effects of scopolamine, an acetylcholine muscarinic receptor antagonist, and physostigmine, an acetylcholinesterase inhibitor, on the learning ability and memory of zebrafish were evaluated using a passive avoidance response test. The zebrafish were trained to stay in a dark compartment to avoid a weight dropping into an acryl shuttle chamber with a central sliding door. The crossing time was increased significantly, from 30.7 ± 40.8 s to 179.3 ± 27.3 s in the training session and 179.9 ± 28.0 s in the test session carried out 2 h later in the controls. When treatment with 200 μM scopolamine was administered for 1 h prior to the training session, the crossing time did not increase. The scopolamine-induced learning deficit was ameliorated by pretreatment with 20 μM physostigmine for 1 h prior to scopolamine treatment; the crossing time was similarly increased, as shown with the controls (60.9 ± 11.5 s, 130.9 ± 27.5 s, and 183.4 ± 26.6 s in the training session and 108.1 ± 23.9 s in the test session). When scopolamine treatment was administered after the training session, the crossing time in the test session was reduced significantly as compared to that noted in the third trial of the training session, which was also ameliorated by physostigmine pretreatment. These results show that scopolamine impairs both the acquisition of passive avoidance response and retention of the learned response, and that physostigmine rescues the amnesic effects of scopolamine in zebrafish.

Acute lecozotan administration increases learning and memory in rats without affecting anxiety or behavioral depression

Lecozotan is a selective serotonergic 5-HT 1A receptor antagonist previously shown to enhance task performance efficiency in aged rhesus monkeys. In the present report we tested the ability of this drug to modify memory and learning in rats during a modified passive avoidance response test, and also tested its effect on anxiety with the elevated plus maze, and behavioral depression in the inescapable swim test. Lecozotan enhanced memory in a dose-dependent manner (0, 0.3, 0.5, 1 and 2 mg/kg; s.c.), or prevented memory impairment previously induced with scopolamine-HCl. No significant changes in anxiety and behavioral depression were detected in animals treated with different doses of lecozotan (0, 0.3, 1 and 2 mg/kg; s.c.) compared to control animals. These results suggest that lecozotan could enhance learning and memory in animals without affecting anxiety or behavioral depression scores and that it could be a viable alternative in the treatment of patients with cognitive deficits such as the Alzheimer's disease.

Tolterodine does not affect memory assessed by passive-avoidance response test in mice

Antimuscarinics are first-line pharmacotherapy for the treatment of overactive bladder. However, because central nervous system cholinergic neurotransmission is involved in cognition, and the central nervous system-permeable antimuscarinics scopolamine and oxybutynin affect memory, cognitive impairment has been noted as a possible side effect of these drugs. We evaluated the effect of tolterodine, an antimuscarinic for overactive bladder, in a mouse passive-avoidance model of memory. Mice were chosen because like humans, mice but not rats, form the pharmacologically active 5-hydroxymethyl metabolite of tolterodine, DD01. In the passive-avoidance test, tolterodine at 1 or 3 mg/kg had no effect on memory; the latency to cross and percentage of animals crossing were comparable to controls. In contrast, scopolamine induced a memory deficit; the latency to cross was decreased, and the number of animals crossing was increased. Therefore, at a dose exceeding therapeutic exposure by six-fold, tolterodine had no effect on memory in the mouse passive-avoidance model, indicating that tolterodine does not disrupt cognitive function in this testing paradigm.

Evaluation of acute bis(7)-tacrine treatment on behavioral functions in 17-day-old and 30-day-old mice, with attention to drug toxicity

Bis(7)-tacrine was evaluated for efficacy on memory retention in mice 17 days of age and 30 days of age. The tests used were a passive-avoidance response test and a measure of spontaneous motor activity. Also, possible drug-induced hepatotoxicity and acute drug toxicity were evaluated. Behavioral studies were performed using a step-through task and an open-field test with a 24-h interval between training and evaluation tests. Bis(7)-tacrine (0.06−20 μmol/kg) was subcutaneously injected 30 min prior to the first session of both test types. During the training session of the step-through task, bis(7)-tacrine treatment reduced (by 46%, P < 0.01) the number of avoidable electric shocks (footshocks) only at a high dose of 20 μmol/kg in mice 17 days of age, but dose-dependently decreased the number of footshocks (10–56%, P < 0.001) in mice 30 days of age. Bis(7)-tacrine treatment at all doses tested did not produce any detectable changes in retention latency in mice 17 days of age, but the drug significantly prolonged retention latency at low doses (1.25 and 2.50 μmol/kg), and not high doses (5–20 μmol/kg), in mice 30 days of age. In the open-field test, bis(7)-tacrine decreased spontaneous motor activity in the acquisition session only at a high dose of 20 μmol/kg in mice 17 days of age and 30 days of age (by 28 and 45%, respectively), but did not affect spontaneous motor activity in the recall session. Bis(7)-tacrine treatment at a dose of 20 μmol/kg produced a more potent hepatotoxic effect in mice 30 days of age than in mice 17 days of age, ( P < 0.05), and the drug caused acute toxicity with comparable potencies in mice of both age groups. In conclusion, mice 30 days of age seemed to be more sensitive than mice 17 days of age to bis(7)-tacrine-induced cognitive function enhancement and hepatotoxicity. Bis(7)-tacrine appears to be more potent and more selective as a cognitive function-enhancing agent than tacrine.

Effect of antimuscarinic drugs used for overactive bladder on learning in a rat passive avoidance response test

Antimuscarinic drugs are used for the treatment of overactive bladder. One adverse effect associated with their use, however, is cognitive impairment arising from their anticholinergic action. Here, we examined the effects of antimuscarinic drugs on learning using a passive avoidance task in rats. Drugs were intravenously administered 10 min before an acquisition trial, followed 24 h later by measurement of latency time in the passive avoidance task in a retention trial. Oxybutynin (0.1–1 mg/kg i.v.), propiverine (1–10 mg/kg i.v.) and scopolamine (0.1–1 mg/kg i.v.) impaired learning at doses of 0.3 mg/kg i.v. or more, 10 mg/kg i.v., and 0.3 mg/kg i.v. or more, respectively. Tolterodine (0.1–1 mg/kg i.v.) tended to impair these functions at a dose of 1 mg/kg i.v. In contrast, darifenacin (0.1–1 mg/kg i.v.) and solifenacin (0.3–3 mg/kg i.v.) showed no impairment of these functions. We also examined the effects of antimuscarinic drugs on learning enhanced by the cholinesterase inhibitor donepezil at a dose of 0.1 mg/kg i.v. in scopolamine-treated rats. Oxybutynin (0.1–1 mg/kg i.v.) impaired these donepezil-enhanced functions, whereas solifenacin (0.3–3 mg/kg i.v.) produced no significant impairment. These results suggest that antimuscarinic drugs such as darifenacin, solifenacin and tolterodine may have less effect on cognitive function in the treatment of patients with overactive bladder.