Offline consolidation of spatial memory: Do the cerebellar output circuits play a role? A study utilizing a Morris water maze protocol in male Wistar rats

Analysis of NAPA Gene Expression in Brain Structures of Wistar Rats during the Formation of Long-Term Spatial Memory and Physical Activity under Stress Situation

In the cerebellum, hippocampus, and prefrontal cortex of mature male Wistar rats with trained spatial navigational skill in the Morris water maze, the transcriptional activity the NAPA gene that regulates the transport and secretion of synaptic vesicles, release of neurotransmitters, and protein degradation was determined by real-time PCR. Animals subjected to forced swimming in a time-matched regime (active control) and naïve rats were used as the comparison groups. Suppression of NAPA gene activity was found in the hippocampus and cerebellum of the active control group, while navigation skill training led to a significant increase in gene expression in all brain structures under study. The findings suggest the existence of specific mechanisms regulating NAPA gene activity during the formation of spatial memory and adaptive behavior under stress conditions.

Mix of almond baru (Dipteryx alata Vog.) and goat whey modulated intestinal microbiota, improved memory and induced anxiolytic like behavior in aged rats

The objective was to evaluate the effects of the consumption of a mix of baru almond and goat whey on memory performance and anxiety parameters related to the intestinal health of rats treated during aging. The animals were divided into three groups and treated by gavage for 10 weeks (n = 10/each group): Control (CT) - distilled water; Baru almond (BA) - 2000 mg of baru/kg of body weight; and Baru + Whey (BW) - 2000 mg of baru + 2000 mg of goat milk whey/kg of body weight. Anxiety behavior, memory, brain fatty acid profile and fecal microbiota were measured. BA and BW realized less grooming, spent more time in the central area of the open field and the open arms, and realized more head dipping in the elevated plus maze. A higher rate of exploration of the new object in the short and long-term memory was observed in BA and BW. There was an increase in the deposition of MUFAs and PUFAs and oleic acid in the brain of BA and BW. Regarding spatial memory, BA and BW performed better, with an emphasis on BW. There was a beneficial modulation of the fecal microbiota with a reduction of the pathogenic genus Clostridia_UFC-014 in BA and BW and an increase in the abundance of metabolic pathways of interest in the brain-gut axis. Thus, consumption of the mix is efficient in beneficially altering the intestinal microbiota, improving memory and anxiolytic-like behavior in rats during aging.

A Liaison Brought to Light: Cerebellum-Hippocampus, Partners for Spatial Cognition

This review focuses on the functional and anatomical links between the cerebellum and the hippocampus and the role of their interplay in goal-directed navigation and spatial cognition. We will describe the interactions between the cerebellum and the hippocampus at different scales: a macroscopic scale revealing the joint activations of these two structures at the level of neuronal circuits, a mesoscopic scale highlighting the synchronization of neuronal oscillations, and finally a cellular scale where we will describe the activity of hippocampal neuronal assemblies following a targeted manipulation of the cerebellar system. We will take advantage of this framework to summarize the different anatomical pathways that may sustain this multiscale interaction. We will finally consider the possible influence of the cerebellum on pathologies traditionally associated with hippocampal dysfunction.

Evaluation of the Activity of Choline Acetyltransferase From Different Synaptosomal Fractions at the Distinct Stages of Spatial Learning in the Morris Water Maze

Accumulated data have evidenced that brain cholinergic circuits play a crucial role in learning and memory; however, our knowledge about the participation of neocortical and hippocampal cholinergic systems in spatial learning needs to be refined. The aim of this study was to evaluate the association of the activity of membrane-bound and soluble choline acetyltransferase (ChAT) in the synaptosomal sub-fractions of the neocortex and hippocampus with performance of the spatial navigation task in the Morris water maze at different temporal stages of memory trace formation. To identify distinct stages of memory formation, rats were trained using a 5-day protocol with four trials per day. The mean escape latency for each trial was collected, and the entire dataset was subjected to principal component analysis. Based on the Morris water maze protocol, there were three relatively distinct stages of memory formation: days 1-2, day 3, and days 4-5. The remotely stored memory trace tested in repeated and reversal learning beginning on day 19 (14 days after the end of initial learning) was associated at the individual level mainly with performance during the second trial on day 21 (the third day or repeated or reversal learning). The ChAT activity data suggest the participation of cortical cholinergic projections mainly in the first stage of spatial learning (automatic sensory processing) and the involvement of hippocampal interneurons in the second stage (error-corrected learning). Cholinergic cortical interneurons participated mainly in the stage of asymptotic performance (days 4-5). It is advisable to evaluate other signalling pathways at the identified stages of memory formation.

Chemical characterization and evaluation of the neuroprotective potential of Indigofera sessiliflora through in-silico studies and behavioral tests in scopolamine-induced memory compromised rats

In the current study, we investigated the phytochemical and neuropharmacological potential of Indigofera sessiliflora, an indigenous least characterized plant widely distributed in deserted areas of Pakistan. The crude extract of the whole plant Indigofera sessiliflora (IS.CR) was preliminary tested in-vitro for the existence of polyphenol content, antioxidant and anticholinesterase potential followed by detailed chemical characterization through UHPLC-MS. Rats administered with different doses of IS.CR (100-300 mg/kg) for the duration of 4-weeks were behaviorally tested for anxiety and cognition followed by biochemical evaluation of dissected brain. The in-silico studies were employed to predict the blood-brain barrier crossing tendencies of secondary metabolites with the elucidation of the target binding site. The in-vitro assays revealed ample phenols and flavonoids content in IS.CR with adequate anti-oxidant and anticholinesterase potential. The dose-dependent anxiolytic potential of IS.CR was demonstrated in open field (OFT), light/dark (L/D) and elevated plus maze (EPM) tests as animals spent more time in open, illuminated and elevated zones (P < 0.05). In the behavioral tests for learning/memory, the IS.CR reversed the scopolamine-induced cognitive deficits, as animals showed better (P < 0.05) spontaneous alternation and discrimination index in y-maze and novel object recognition (NOR) tests. Similarly, as compared to amnesic rats, the step-through latencies were increased (P < 0.05) and escape latencies were decreased (P < 0.05) in passive avoidance (PAT) and Morris water maze (MWM) tests, respectively. Biochemical analysis of rat brains showed significant reduction in malondialdehyde and acetylcholinesterase levels, alongwith preservation of glutathione peroxidase and superoxide dismutase activity. The docking studies further portrayed a possible interaction of detected phytoconstituents with acetylcholinesterase target. The results of the study show valuable therapeutic potential of phytoconstituents present in IS.CR to correct the neurological disarrays which might be through antioxidant activity or via modulation of GABAergic and cholinergic systems by artocommunol, 1,9-dideoxyforskolin and 6E,9E-octadecadienoic acid.

Sensorineural hearing loss may lead to dementia-related pathological changes in hippocampal neurons

Presbycusis contributes to cognitive decline and Alzheimer's disease. However, most research in this area involves clinical observations and statistical modeling, and few studies have examined the relationship between hearing loss and the molecular changes that lead to cognitive dysfunction. The present study investigated whether hearing loss contributes to dementia in the absence of aging and noise using a mouse model of severe bilateral hearing loss induced by kanamycin (1000 mg/kg) and furosemide (400 mg/kg). Immunohistochemistry, silver staining, immunofluorescence analysis, and Western blotting were used to observe pathological changes in different regions of the hippocampus in animals with hearing loss. Changes in the cognitive function of animals with hearing loss were assessed using the Morris water maze test. The results showed that neurons began to degenerate 60 days after hearing loss, and this degeneration was accompanied by structural disorganization and decreased neurogenesis. The level of phosphorylated tau increased over time. Increases in escape latency and distance traveled during the training phase of the Morris water maze test were observed 90 days after hearing loss. Activated microglia and astrocytes with increased levels of inflammatory cytokines, such as tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) were detected in the hippocampus. These results suggest that hearing loss alone causes neuronal degeneration, inhibition of neurogenesis, increased tau protein phosphorylation, and increased neuroinflammation in the hippocampus. Early intervention in individuals with hearing loss may reduce the risk of cognitive decline.

Chemical Profiling and Dose-Dependent Assessment of Fear Reducing and Memory-Enhancing Effects of Solanum virginianum in Rats

The current study was planned to investigate the pharmacological basis of Solanum virginianum extract (SV.CR) pertaining to anxiolytic, antidepressant and memory-enhancing effects in rats. The SV.CR was analyzed in-vitro for phytoconstituents, antioxidant potential and anticholinesterase activity. The rats treated in a dose-dependent manner (25, 50 and 100 mg/kg of SV.CR) were subjected to behavioral tests for anxiety, depression and memory judgment followed by biochemical studies. A notable dose-dependent anxiolytic potential of SV.CR was observed in elevated plus maze and open field tests (P < 0.05). The decreased immobility time of the treated rats in the forced swim test (P < 0.01) unveiled the plant’s potential to reduce depression. Moreover, SV.CR treatment also reversed scopolamine-impaired cognition (P < 0.05) in various deployed memory and learning tasks. Biochemical studies of brain homogenates of SV.CR treated animals demonstrated decreased anticholinesterase activity and lipid peroxidation levels whereas increased levels of superoxide dismutase and glutathione peroxidase (P < 0.05 vs scopolamine group) were noted. The scientific validation of the study supported the use of Solanum virginianum in reducing anxiety, depression and amnesia in experimental models. Phytoconstituents in SV.CR such as oleanolic acid and caffeic acid might have played a significant neuroprotective role via modulation of oxidative stress and neurochemical aspects.

Naringenin alleviates cognition deficits in high-fat diet-fed SAMP8 mice

Naringenin is a natural dihydro flavonoid that is abundant in grapefruit. Previous studies suggested the cognition protective effect of naringenin in various cognitive deficits models, such as type 2 diabetic rat model and chemicals (e.g., lipopolysaccharide, scopolamine) treated rodents. However, the effects of naringenin on aging animals and the potential mechanisms are still unclear. In this study, we investigated the influence of naringenin administration on learning deficits in aging mice. High-fat diet-fed SAMP8 mice were employed as an age-related model of Alzheimer's disease. Dietary administration of 0.2% naringenin for 12 weeks significantly improved the spatial learning and memory performance of the high-fat diet-fed SAMP8 mice in both Barnes Maze test and Morris Water Maze test. Further mechanism research indicated that naringenin reduced Aβ production, tau-hyperphosphorylation, oxidative stress, and neuroinflammation in the brain. This research provides further evidence for the treatment effect of naringenin on Alzheimer's disease. PRACTICAL APPLICATIONS: Naringenin, also known as 4',5,7-thrihydroxyflflavanone, is a natural dihydro flavonoid that is abundant in grapefruit and other citrus fruits. The current study first demonstrated the improvement effect of naringenin on cognition deficits in HFD-fed SAMP8 mice, an aging mouse model. Potential mechanisms were also systematically explained by exploring the amyloid-β (Aβ) accumulation, tau hyperphosphorylation, oxidative stress, and neuroinflammation in the brain of mice. This study provides further evidence for the utilization of naringenin as an effective treatment agent for Alzheimer's disease.