Effect of ramosetron, a 5-HT3 receptor antagonist on the severity of seizures and memory impairment in electrical amygdala kindled rats

The entorhinal cortex (EC) plays a pivotal role in epileptogenesis and seizures. EC expresses high density of serotonergic receptors, especially 5-HT3 receptors. Cognitive impairment is common among people with epilepsy. The present study investigated the role of 5-HT3 receptor on the severity of seizures and learning and memory impairment by electrical kindling of amygdala in rats. The amygdala kindling was conducted in a chronic kindling manner in male Wistar rats. In fully kindled animals, ramosetron (as a potent and selective 5-HT3 receptor antagonist) was microinjected unilaterally (ad doses of 1, 10 or 100 µg/0.5 µl) into the EC 5 min before the novel object recognition (NOR) and Y-maze tests or kindling stimulations. Applying ramosetron at the concentration of 100 μg/0.5 µl (but not at 1 and 10 µg/0.5 µl) reduced afterdischarge (AD) duration and increased stage 4 latency in the kindled rats. Moreover, the obtained data from the NOR test showed that treatment by ramosetron (10 and 100 µg/0.5 µl) increased the discrimination index in the fully kindled animals. Microinjection of ramosetron (10 and 100 µg/0.5 µl) in fully kindled animals reversed the kindling induced changes in the percentage of spontaneous alternation in Y-maze task. The findings demonstrated an anticonvulsant role for a selective 5-HT3 receptor antagonist microinjected into the EC, therefore, suggesting an excitatory role for the EC 5-HT3 receptors in the amygdala kindling model of epilepsy. This anticonvulsive effect was accompanied with a restoring effect on cognitive behavior in NOR and Y-maze tests.

A High-Methionine Diet for One-Week Induces a High Accumulation of Methionine in the Cerebrospinal Fluid and Confers Bipolar Disorder-like Behavior in Mice

Methionine (Met) is considered the most toxic amino acid in mammals. Here, we investigated biochemical and behavioral impacts of ad libitum one-week feeding of high-Met diets on mice. Adult male mice were fed the standard rodent diet that contained 0.44% Met (1×) or a diet containing 16 graded Met doses (1.2×–13×). High-Met diets for one-week induced a dose-dependent decrease in body weight and an increase in serum Met levels with a 2.55 mM peak (versus basal 53 µM) on the 12×Met diet. Total homocysteine (Hcy) levels were also upregulated while concentrations of other amino acids were almost maintained in serum. Similarly, levels of Met and Hcy (but not the other amino acids) were highly elevated in the cerebrospinal fluids of mice on the 10×Met diet; the Met levels were much higher than Hcy and the others. In a series of behavioral tests, mice on the 10×Met diet displayed increased anxiety and decreased traveled distances in an open-field test, increased activity to escape from water soaking and tail hanging, and normal learning/memory activity in a Y-maze test, which were reflections of negative/positive symptoms and normal cognitive function, respectively. These results indicate that high-Met ad libitum feeding even for a week can induce bipolar disorder-like disease models in mice.

Neuroprotective Effects of Probiotic-Supplemented Diet on Cognitive Behavior of 3xTg-AD Mice

Alzheimer’s disease (AD) is recognized as one of the most common types of senile dementia. AD patients first suffer memory loss for recent events (short-term memory impairment). As the disease progresses, they are deprived of self-awareness. This study aims to explore the effects of a probiotic-supplemented diet on the cognitive behaviors and pathological features of mouse models of Alzheimer’s disease (AD). Mice in the control group and the 3xTg-AD group were fed a regular diet and a probiotic-supplemented diet, respectively, for 20 weeks. Behavioral experiments like Morris’s water maze and Y maze were conducted. Then, feces of mice were collected for 16S sRNA gene sequencing for microorganisms. In the end, soluble and insoluble Aβ40 and Aβ42 in the hippocampus and cortex of mice in each group were quantitatively analyzed with a double-antibody Sandwich ELISA. The expression levels of tau protein and gliocyte in the hippocampus and cortex were detected using the Western Blot method. The result of the Morris water maze experiment indicated that, in the place navigation test, the mice in the 3xTg-AD group experienced a significant decline in the learning ability and a longer escape latency and in the space exploration test, the swimming time of mice in the 3xTg-AD group in the target quadrant decreased and after being treated with the probiotic diet, mice in the 3xTg-AD group had improved learning and memory ability. The result of Y maze showed that the probiotic diet can improve the spontaneous alternation accuracy of mice in the 3xTg-AD group. The result of 16s rRNA gene sequencing showed that, compared with mice in the WT group, those in the 3xTg-AD group experienced a change in the intestinal flora. The Western Blot result displayed a decreased expression level of tau (pS202) ( P < 0.05 ) and decreased expression levels of Iba-1 and GFAP ( P < 0.05 ). The result of the ELISA experiment showed decreased levels of soluble and insoluble Aβ40 and Aβ42 in 3xTg-AD mice ( P < 0.05 ). In conclusion, a probiotic diet can prevent and treat AD by improving the intestinal flora of 3xTg-AD.

Nigella sativa Oil Preserved Anxiety-Like, Motor and Memory Related Behaviours and Neuronal Integrity in Dichlorvos Induced Acetyl Cholinesterase Inhibitions in Rats

Organophosphates are irreversible cholinesterase (ChE) inhibitors with neurological consequences, and there is not yet an effective antidote. Here, we investigated the effects of Nigella sativa oil (NSO) on the ChE inhibition, neurobehavioural and histopathological changes following dichlorvos (DDVP) ingestions in rats. Thirty-two male Wistar rats were randomised into four groups, receiving 1 ml/kg of normal saline, 8.8 mg/kg of DDVP, 8.8 mg/kg of DDVP and 1 ml/kg of NSO, and 1 ml/kg of NSO only respectively, for 14 consecutive days. Locomotor, anxiety-like behaviours and spatial working memory were assessed on the 14th day, using open field (OF), Y-maze and modified elevated plus maze paradigms. The rats were euthanized on the 15th day and the brains excised; three brains were fixed for histopathology, and the other five prepared for biochemical analysis of acetyl cholinesterase (AChE). DDVP exposure caused significant reductions in frontal, amygdala and cerebella AChE activity, spontaneous alternations, line crossing and rearing frequencies and time in centre square, and caused increase in freezing period, transfer latency and necrotic-like cells. NSO intervention was able to reverse DDVP effects on AChE activities, explorative, locomotor, anxiety and spatial memory behaviours in co-exposed rats. It also preserved the histological integrity of the investigated brain regions. It can be concluded that NSO, may be potent against organophosphates induced neurotoxicity and their neurobehavioural consequences through the modulation of AChE activities.

Do predators prefer toxic animals? A case of chemical discrimination by an asian snake that sequesters firefly toxins

Several Asian natricine snakes of the genus Rhabdophis feed on toads and sequester steroidal cardiac toxins known as bufadienolides (BDs) from them. A recent study revealed that species of the R. nuchalis Group ingest lampyrine fireflies to sequester BDs. Although several species of fireflies are distributed in the habitat of the R. nuchalis Group, only lampyrine fireflies, which have BDs, included in the diet of these snakes. Thus, we hypothesized that the R. nuchalis Group chemically distinguishes fireflies that have BDs from those that do not have BDs. We also predicted that the R. nuchalis Group detects BDs as the chemical cue of toxin source. To test these predictions, we conducted three behavioral experiments using R. chiwen, which belongs to the R. nuchalis Group. In the first experiment, R. chiwen showed a moderate tongue flicking response to cinobufagin, a compound of BDs. On the other hand, the snake showed a higher response to the chemical stimuli of lampyrine fireflies (BD fireflies) than those of lucioline fireflies (non-BD fireflies). In the second experiment, in which we provided live BD and non-BD fireflies, the snake voluntarily consumed only the former. In the third, a Y-maze experiment, the snake tended to select the chemical trail of BD fireflies more frequently than that of non-BD fireflies. These results demonstrated that R. chiwen discriminates BD fireflies from non-BD fireflies, but the prediction that BDs are involved in this discrimination was not fully supported. To identify the proximate mechanisms of the recognition of novel toxic prey in the R. nuchalis Group, further investigation is necessary.

Studying some neuroprotective effects of Calotropis procera extracts against scopolamine- induced neuropschiatric comorbidities in a rodent model of epilepsy

Many plants are largely used in alternative medicine of Burkina Faso for neuropsychiatric disorders treatment. However, their neuro-pharmacological properties are less evaluated through scientific studies. The present study aims to evaluate the neuroprotective effect of Calotropis procera leaves and root-bark aqueous extract, focusing on a scopolamine-induced model of epilepsy in rodents. In this study, we evaluated this plant extracts possible protective effects on the central nervous system, through the behavioral tests and the enzymes activity assays. Thus, elevated plus-maze test and Y-maze task were used to evaluate animals behavioral and UV/visible spectrophotometer methods were used to evaluate the enzyme’s activities in brain’s supernatant. Our results are showing no significant protective effects of leaves extract, but it revealed a significant neuroprotective effect of root-bark aqueous extract, as well as in the behavioral tests and the brain’s oxidative enzymes specific activity evaluation. Indeed, anti-amnesic and anxiolytic activities were observed through Y maze task and elevated plus maze tests for the groups of animals receiving root-bark extract (100 mg/kg b.w.). In these test, inhibition of disturbances of Time spent in Open Arms, Spontaneous Alternation, and Transfer Latency induced after scopolamine administration were recorded with animals received root-bark extract. Likewise, the superoxide dismutase and catalase activity disturbance induced by scopolamine were also inhibited in root-bark extract pre-administered group. Thus, our study provides biochemical and neuro-pharmacological data for traditional use of C. procera for neuropsychiatric disorders treatment, including scopolamine-induced epilepsy symptoms (mainly referring to the psychiatric comorbidities of this disorder).

Treadmill Exercise During Cerebral Hypoperfusion Has Only Limited Effects on Cognitive Function in Middle-Aged Subcortical Ischemic Vascular Dementia Mice

Clinical and basic research suggests that exercise is a safe behavioral intervention and is effective for improving cognitive function in cerebrovascular diseases, including subcortical ischemic vascular dementia (SIVD). However, most of the basic research uses young animals to assess the effects of exercise, although SIVD is an age-related disease. In this study, therefore, we used middle-aged mice to examine how treadmill exercise changes the cognitive function of SIVD mice. As a mouse model of SIVD, prolonged cerebral hypoperfusion was induced in 8-month-old male C57BL/6J mice by bilateral common carotid artery stenosis. A week later, the mice were randomly divided into two groups: a group that received 6-week treadmill exercise and a sedentary group for observation. After subjecting the mice to multiple behavioral tests (Y-maze, novel object recognition, and Morris water maze tests), the treadmill exercise training was shown to only be effective in ameliorating cognitive decline in the Y-maze test. We previously demonstrated that the same regimen of treadmill exercise was effective in young hypoperfused-SIVD mice for all three cognitive tests. Therefore, our study may indicate that treadmill exercise during cerebral hypoperfusion has only limited effects on cognitive function in aging populations.

2-Dodecyl-6-Methoxycyclohexa-2,5-Diene-1,4-Dione Ameliorates Diabetic Cognitive Impairment Through Inhibiting Hif3α and Apoptosis

Diabetes mellitus (DM) is an independent risk factor for cognitive impairment. Although the etiology of diabetic cognitive impairment is complex and multifactorial, the hippocampus neuronal apoptosis is recognized as a main cause of diabetes-induced cognitive impairment. 2-Dodecyl-6-methoxycyclohexa-2,5-diene-1,4-dione (DMDD) was purified from the roots of Averrhoa carambola L. Previous research demonstrated that DMDD was safe and effective in delaying some diabetic complications. However, the efficacy of DMDD to ameliorate diabetic cognitive impairment in type 2 diabetes mice has not been reported. In the present study, the behavioral evaluation was performed by Y maze and novel object recognition in db/db mice. Gene expression profiles were detected using mouse lncRNA microarray analysis in the hippocampi of db/db mice. Changes in the neurodegeneration-associated proteins and the apoptosis-related proteins were determined in both db/db mice and high glucose-treated HT22 cells by Western blotting. We observed that DMDD treatment significantly ameliorated the spatial working memory and object recognition memory impairment in db/db mice. Further study showed that neurodegeneration-associated protein tau was decreased after DMDD treatment in the hippocampi of db/db mice. Eleven lncRNAs and four mRNAs including pro-apoptotic gene Hif3a were significantly differently expressed after DMDD treatment in the hippocampi of db/db mice. The expression of Hif3a, cleaved parp, and caspase 3 proteins was significantly increased in the hippocampi of diabetic db/db mice compared with db/m control mice and then decreased after DMDD treatment. Similar beneficial effects of DMDD were observed in HG-treated HT22 cells. These data indicate that DMDD can alleviate cognitive impairment by inhibiting neuronal apoptosis through decreasing the expression of pro-apoptotic protein Hif3a. In conclusion, our study suggests that DMDD has great potential to be a new preventive and therapeutic compound for diabetic cognitive impairment.

EXPLORE THE IMPACT OF NOISE STRESS INDUCED BRAIN WAVE PATTERN AND BEHAVIOUR ALTERATIONS IN WISTAR ALBINO RATS

Objective: The aim of the study is to investigate the impact of noise-induced stress and electroencephalogram (EEG) with behavioral alteration in male Wistar albino Rats. Methods: Adult albino rats were randomly divided into three groups. Each group contains six animals. Rats exposed to acute and sub-acute noise, stress (100 dB/4 h) were compared with control animals and assessed for learning and memory using an Eight-arm radial maze, Y-maze, T-maze and also monitoring of brain electrical activity showed by the electro encephalography. Results: The reference memory and working memory error increases, in acute and sub-acute noise stress. The amplitude and frequency also increase in frontal and occipital lobar when compared to control animals. Conclusion: Animals were exposed to noise stress showed learning and memory impairment and also changes in EEG wave pattern.