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.

Sensorimotor and sensory gating in depression, anxiety, and their comorbidity.

OBJECTIVES: Abnormal attentional and cognitive processes are thought to increase the risk for depression and anxiety. To improve understanding of brain mechanisms of anxiety and depressive disorders and condition of their comorbidity, the study of early attentional processes was provided. METHODS: Participants were patients with depressive (80 s.), anxiety (69 s.), and comorbid (41 s.) disorders, and healthy volunteers (50 s.). Acoustic startle response (ASR) and P50 component of the auditory event-related potential were recorded. RESULTS: In the ASR model decreased startle response amplitude at the left eye in patients with comorbid disorder was found, and ASR latency was lengthened in all clinical groups. Deficit of prepulse inhibition was unique for comorbid disorder, and might be considered as risk of evolution to more serious condition. Reduced prepulse facilitation was revealed in patients with comorbid and anxiety disorders. In P50 suppression paradigm decreased S1 response amplitude was revealed in all clinical groups, P50 latency was prolonged in depressive and comorbid patients, and P50 suppression deficit was observed in depression and anxiety groups. CONCLUSIONS: The obtained results might be useful for development of integrative neural models of comorbidity of anxiety and depression, and elaboration of diagnostic and therapeutic approaches.

Opposite Pathways of Cholinergic Mechanisms of Hypoxic Preconditioning in the Hippocampus: Participation of Nicotinic α7 Receptors and Their Association with the Baseline Level of Startle Prepulse Inhibition.

(1) Background. A one-time moderate hypobaric hypoxia (HBH) has a preconditioning effect whose neuronal mechanisms are not studied well. Previously, we found a stable correlation between the HBH efficiency and acoustic startle prepulse inhibition (PPI). This makes it possible to predict the individual efficiency of HBH in animals and to study its potential adaptive mechanisms. We revealed a bi-directional action of nicotinic α7 receptor agonist PNU-282987 and its solvent dimethyl sulfoxide on HBH efficiency with the level of PPI > or < 40%. (2) The aim of the present study was to estimate cholinergic mechanisms of HBH effects in different brain regions. (3) Methods: in rats pretested for PPI, we evaluated the activity of synaptic membrane-bound and water-soluble choline acetyltransferase (ChAT) in the sub-fractions of 'light' and 'heavy' synaptosomes of the neocortex, hippocampus and caudal brainstem in the intact brain and after HBH. We tested the dose-dependent influence of PNU-282987 on the HBH efficiency. (4) Results: PPI level and ChAT activity correlated negatively in all brain structures of the intact animals, so that the values of the latter were higher in rats with PPI < 40% compared to those with PPI > 40%. After HBH, this ChAT activity difference was leveled in the neocortex and caudal brainstem, while for membrane-bound ChAT in the 'light' synaptosomal fraction of hippocampus, it was reversed to the opposite. In addition, a pharmacological study revealed that PNU-282987 in all used doses and its solvent displayed corresponding opposite effects on HBH efficiency in rats with different levels of PPI. (5) Conclusion: We substantiate that in rats with low and high PPI two opposite hippocampal cholinergic mechanisms are involved in hypoxic preconditioning, and both are implemented by forebrain projections via nicotinic α7 receptors. Possible causes of association between general protective adaptation, HBH, PPI, forebrain cholinergic system and hippocampus are discussed.

AUDITORY EVOKED POTENTIALS EVIDENCE FOR DIFFERENCES IN INFORMATION PROCESSING BETWEEN HIGH AND LOW HYPNOTIZABLE SUBJECTS.

N100 and P300 auditory evoked potentials in 2-stimulus oddball paradigm were analyzed in high (HH, n = 18) and low (LH, n = 15) hypnotizable participants under waking condition. LH subjects committed more errors than HH subjects. HH subjects demonstrated shorter N100 latencies at frontal electrodes and significant N100 differences between target and nontarget stimuli (higher N100 amplitude and increased latency at parietal sites to targets vs. nontargets), whereas LH subjects failed to show any differences. The overall increase of P300 amplitude with frontal-central localization of P300 maximum was found in HH subjects compared to LH subjects. The obtained results support the psychophysiological model of HH individuals having more effective frontal attentional systems involved in detecting, integrating, and filtering relevant information.

The Neurogenesis Actuator and NR2B/NMDA Receptor Antagonist Ro25-6981 Consistently Improves Spatial Memory Retraining Via Brain Region-Specific Gene Expression.

NR2B-containing NMDA (NR2B/NMDA) receptors are important in controlling neurogenesis and are involved in generating spatial memory. Ro25-6981 is a selective antagonist at these receptors and actuates neurogenesis and spatial memory. Inter-structural neuroanatomical profiles of gene expression regulating adult neurogenesis and neuroapoptosis require examination in the context of memory retrieval and reversal learning. The aim was to investigate spatial memory retrieval and reversal learning in relation to gene expression-linked neurogenetic processes following blockade of NR2B/NMDA receptors by Ro25-6981. Rats were trained in Morris water maze (MWM) platform location for 5 days. Ro25-6981 was administered (protocol days 6-7) followed by retraining (days 15-18 or 29-32). Platform location was tested (on days 19 or 33) then post-mortem brain tissue sampling (on days 20 or 34). The expression of three genes known to regulate cell proliferation (S100a6), differentiation (Ascl1), and apoptosis (Casp-3) were concomitantly evaluated in the hippocampus, prefrontal cortex, and cerebellum in relation to the MWM performance protocol. Following initial training, Ro25-6981 enhanced visuospatial memory retrieval performance during further retraining (protocol days 29-32) but did not influence visuospatial reversal learning (day 33). Hippocampal Ascl1 and Casp-3 expressions were correspondingly increased and decreased while cerebellar S100a6 and Casp-3 activities were decreased and increased respectively 27 days after Ro25-6981 treatment. Chronological analysis indicated a possible involvement of new mature neurons in the reconfiguration of memory processes. This was attended by behavioral/gene correlations which revealed direct links between spatial memory retrieval enhancement and modified gene activity induced by NR2B/NMDA receptor blockade and upregulation.

COMT and GAD1 gene polymorphisms are associated with impaired antisaccade task performance in schizophrenic patients.

Genetic influences modulating executive functions engaging prefrontal cortical brain systems were investigated in 141 male subjects. The effects of variations in two genes implicated in dopamine and GABA activities in the prefrontal cortex: rs4680 (Val158/Met polymorphism of the catechol-o-methyltransferase gene-COMT) and rs3749034 (C/T) substitution in the promoter region of the glutamic acid decarboxylase gene (GAD1) were studied on antisaccade (AS) performance in healthy subjects and schizophrenic patients. Genotyping revealed a trend towards a reduced proportion of COMT Val/Met heterozygotes and a significantly increased frequency of the GAD1 rs3749034 C allele in schizophrenic patients relative to controls. Patients had elevated error rates, increased AS latencies and increased latency variability (coefficient of variation) compared to controls. The influence of polymorphisms was observed only in patients but not in controls. A substantial effect of the COMT genotype was noted on the coefficient of variation in latency, and this measure was higher in Val homozygotes compared to Met allele carriers (p < 0.05) in the patient group. The outcome from rs3749034 was also disclosed on the error rate (higher in T carriers relative to C homozygotes, p < 0.01) and latency (increased in C homozygotes relative to T carriers, p < 0.01). Binary logistic regression showed that inclusion of the genotype factor (i.e., selective estimation of antisaccade measures in CC carriers) considerably increased the validity of the diagnostic model based on the AS measures. These findings may well be derived from specific genetic associations with prefrontal cortex functioning in schizophrenia.

COMT Genotype and Sensory and Sensorimotor Gating in High and Low Hypnotizable Subjects.

We investigated the association between hypnotizability, COMT polymorphism, P50 suppression ratio, and prepulse inhibition of acoustic startle response (ASR) in 21 high (HH) and 19 low (LH) hypnotizable subjects. The frequency of Met/Met carriers of COMT polymorphysm was higher in HH than in LH group (33.3% versus 10.6%, p = .049). Increased ASR amplitude and latency and decreased prepulse inhibition at 120 ms lead interval were found in the HH compared to the LH group. The effect of COMT genotype on prepulse inhibition was observed in LH group only. No between-group differences in P50 measures were found. The obtained results suppose the participation of dopamine system in mechanisms of hypnotizability and different allocation of attentional resources in HH and LH subjects.

Startle Modification and P50 Gating in Schizophrenia Patients and Controls: Russian Population.

Prepulse modification of the acoustic startle response (ASR) and P50 gating are potential neurophysiological endophenotypes of schizophrenia and may be used in the construction of valid clinical biomarkers. Such approach requires a large amount of data obtained in the representative samples from different gender, socio-typological and ethnic groups, replicating studies using the similar protocols and meta-analyses. This is a replication study of ASR and the first study of P50 suppression in Russian patients with schizophrenia (n = 28) and healthy controls (n = 25). ASR and P50 were estimated according to standard protocols. Patients exhibited increased baseline ASR latency (d = 0.35, p = .026) and reduced prepulse inhibition (PPI) at 60 ms interval (d = 0.39, p = .003) and 120 ms interval (d = 0.37, p = .005) relative to controls. In the P50 test patients displayed greater S2 response amplitude (d = 0.24, p = .036) and deficit of P50 suppression (d = 0.43, p = .001). No correlations of PPI and P50 suppression were found in both groups. Only in controls prepulse ASR facilitation (at 2500 ms interval) positively correlated with P50 suppression (r = -.514, p = .013). In patients PPI displayed significant correlations with Difficulty in abstract thinking (N5: r = -.49, p = .005) and Hallucination (P3: r = .40, p = .036) PANSS scales. Logistic regression showed that the combination of PPI and P50 suppression could serve as a diagnostic predictor. Obtained results demonstrated that both PPI and P50 could be regarded as potential schizophrenia biomarkers in Russian population.

Comparative study of the neuroprotective and nootropic activities of the carboxylate and amide forms of the HLDF-6 peptide in animal models of Alzheimer's disease.

A comparative study of the neuroprotective and nootropic activities of two pharmaceutical substances, the HLDF-6 peptide (HLDF-6-OH) and its amide form (HLDF-6-NH2), was conducted. The study was performed in male rats using two models of a neurodegenerative disorder. Cognitive deficit in rats was induced by injection of the beta-amyloid fragment 25-35 (ßA 25-35) into the giant-cell nucleus basalis of Meynert or by coinjection of ßA 25-35 and ibotenic acid into the hippocampus. To evaluate cognitive functions in animals, three tests were used: the novel object recognition test, the conditioned passive avoidance task and the Morris maze. Comparative analysis of the data demonstrated that the neuroprotective activity of HLDF-6-NH2, evaluated by improvement of cognitive functions in animals, surpassed that of the native HLDF-6-OH peptide. The greater cognitive/ behavioral effects can be attributed to improved kinetic properties of the amide form of the peptide, such as the character of biodegradation and the half-life time. The effects of HLDF-6-NH2 are comparable to, or exceed, those of the reference compounds. Importantly, HLDF-6-NH2 exerts its effects at much lower doses than the reference compounds.

Startle modification and P50 gating in schizophrenia patients and controls: Russian population

Prepulse modification of the acoustic startle response (ASR) and P50 gating are potential neurophysiological endophenotypes of schizophrenia and may be used in the construction of valid clinical biomarkers. Such approach requires a large amount of data obtained in the representative samples from different gender, socio-typological and ethnic groups, replicating studies using the similar protocols and meta-analyses. This is a replication study of ASR and the first study of P50 suppression in Russian patients with schizophrenia (n = 28) and healthy controls (n = 25). ASR and P50 were estimated according to standard protocols. Patients exhibited increased baseline ASR latency (d = 0.35, p = .026) and reduced prepulse inhibition (PPI) at 60 ms interval (d = 0.39, p = .003) and 120 ms interval (d = 0.37, p = .005) relative to controls. In the P50 test patients displayed greater S2 response amplitude (d = 0.24, p = .036) and deficit of P50 suppression (d = 0.43, p = .001). No correlations of PPI and P50 suppression were found in both groups. Only in controls prepulse ASR facilitation (at 2500 ms interval) positively correlated with P50 suppression (r = -.514, p = .013). In patients PPI displayed significant correlations with Difficulty in abstract thinking (N5: r = -.49, p = .005) and Hallucination (P3: r = .40, p = .036) PANSS scales. Logistic regression showed that the combination of PPI and P50 suppression could serve as a diagnostic predictor. Obtained results demonstrated that both PPI and P50 could be regarded as potential schizophrenia biomarkers in Russian population (AU)

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Learning ability is a key outcome determinant of GSK-3 inhibition on visuospatial memory in rats.

Learning aptitude has never been a focus of visuospatial performance studies, particularly on memory consolidation and reconsolidation. The aim of this study was to determine the consequences of learning ability on memory consolidation/reconsolidation following inhibition of glucose synthase kinase-3 (GSK-3) by 4-benzyl-2-methyl-1,2,4-thiadiazolidine-3,5-dione (TDZD-8). The anxiety-like nature of rats was characterized in the elevated plus maze. The rats were then trained for four days in the Morris water maze (MWM) and classified as 'superior', 'intermediate' or 'inferior' learners. There were no major differences between superior, intermediate or inferior learners with respect to anxiety which might have influenced learning. After training (day-5), TDZD-8 (2.0 mg/kg) was administered and half of the cohort were exposed to a MWM retrieval trial. Ten days later, animals were subjected to repeated MWM learning. TDZD-8 without a retrieval trial impaired subsequent reconsolidation in inferior learners, but enhanced it in superior learners. There was no modification of performance in intermediate learners. In TDZD-8-treated subjects exposed to retrieval, the pattern of outcomes was identical whereby impairment of reconsolidation occurred in inferior learners, enhancement occurred in superior learners but there was no modification of performance in intermediate learners. Thus, learning ability was a key determinant of the qualitative outcome from GSK-3 inhibition on visuospatial memory.

Distinct functional brain regional integration of Casp3, Ascl1 and S100a6 gene expression in spatial memory.

Evaluating the brain structural expression of defined genes involved in basic biological processes of neurogenesis, apoptosis or neural plasticity may facilitate the understanding of genetic mechanisms underlying spatial memory. The aim of the present study was to compare Ascl1, Casp3 and S100a6 gene expression in the hippocampus, prefrontal cortex and cerebellum of adult rats in water maze spatial memory performance. After four days training, the mean platform time (<10s) was evidence of stable long-term spatial memory formation. Real time PCR analysis revealed a positive inter-structural correlation for S100a6/Casp gene expression between the prefrontal cortex and the cerebellum but a negative correlation for S100a6/Ascl1 transcribed genes between the prefrontal cortex and hippocampus during swimming in the active controls. However, during spatial memory performance there was only one inter-structural correlation between the prefrontal cortex and cerebellum with respect to Casp3 expression, though there were intra-structural correlations between Casp3/Ascl1 transcriptions within the prefrontal cortex and hippocampus as well as between Ascl1/S100a6 in the cerebellum. In active learners versus naive controls, the transcrption of all genes was augmented in the prefrontal cortex but Casp3 and Ascl1 were also elevated in hippocampus whilst only S100a6 increased in the cerebellum. The findings endorsed the role of the hippocampus in memory acquisition in addition to an integrative relationship with the prefrontal cortex and cerebellum. This structural and molecular configuration is important for creation of novel neural circuitry for consolidation and reconsolidation of memory trace with an involvement of coupled processes of neurogenesis, apoptosis or neural plasticity.

Dicholine salt of succinic acid, a neuronal insulin sensitizer, ameliorates cognitive deficits in rodent models of normal aging, chronic cerebral hypoperfusion, and beta-amyloid peptide-(25-35)-induced amnesia.

BACKGROUND: Accumulated evidence suggests that insulin resistance and impairments in cerebral insulin receptor signaling may contribute to age-related cognitive deficits and Alzheimer's disease. The enhancement of insulin receptor signaling is, therefore, a promising strategy for the treatment of age-related cognitive disorders. The mitochondrial respiratory chain, being involved in insulin-stimulated H2O2 production, has been identified recently as a potential target for the enhancement of insulin signaling. The aim of the present study is to examine: (1) whether a specific respiratory substrate, dicholine salt of succinic acid (CS), can enhance insulin-stimulated insulin receptor autophosphorylation in neurons, and (2) whether CS can ameliorate cognitive deficits of various origins in animal models. RESULTS: In a primary culture of cerebellar granule neurons, CS significantly enhanced insulin-stimulated insulin receptor autophosphorylation. In animal models, CS significantly ameliorated cognitive deficits, when administered intraperitoneally for 7 days. In 16-month-old middle-aged C57Bl/6 mice (a model of normal aging), CS enhanced spatial learning in the Morris water maze, spontaneous locomotor activity, passive avoidance performance, and increased brain N-acetylaspartate/creatine levels, as compared to the age-matched control (saline). In rats with chronic cerebral hypoperfusion, CS enhanced spatial learning, passive avoidance performance, and increased brain N-acetylaspartate/creatine levels, as compared to control rats (saline). In rats with beta-amyloid peptide-(25-35)-induced amnesia, CS enhanced passive avoidance performance and increased activity of brain choline acetyltransferase, as compared to control rats (saline). In all used models, CS effects lasted beyond the seven-day treatment period and were found to be significant about two weeks following the treatment. CONCLUSION: The results of the present study suggest that dicholine salt of succinic acid, a novel neuronal insulin sensitizer, ameliorates cognitive deficits and neuronal dysfunctions in animal models relevant to age-related cognitive impairments, vascular dementia, and Alzheimer's disease.