Long-term Potentiation Of Synaptic Transmission Research Articles

Resveratrol differentially affects MMP-9 release from neurons and glia; implications for therapeutic efficacy.

Resveratrol, a naturally occurring polyphenol that activates sirtuin 1 (SIRT1), has been shown to reduce overall levels of matrix metalloprotease-9 (MMP-9) in cerebrospinal fluid (CSF) samples from patients with Alzheimer's dementia (AD). Depending on the site of release, however, MMP-9 has the potential to improve or impair cognition. In particular, its release from microglia or pericytes proximal to the blood brain barrier can damage the basement membrane, while neuronal activity-dependent release of this protease from glutamatergic neurons can instead promote dendritic spine expansion and long-term potentiation of synaptic plasticity. In the present study, we test the hypothesis that resveratrol reduces overall MMP-9 levels in CSF samples from patients with APOE4, an allele associated with increased glial inflammation. We also examine the possibility that resveratrol reduces inflammation-associated MMP release from cultured glia but spares neuronal activity-dependent release from cultured cortical neurons. We observe that resveratrol decreases overall levels of MMP-2 and MMP-9 in CSF samples from AD patients. Resveratrol also reduces CSF levels of tissue inhibitor of metalloproteinases-1 (TIMP-1), glial-derived protein that restricts long-term potentiation of synaptic transmission, in individuals homozygous for APOE4. Consistent with these results, we observe that resveratrol reduces basal and lipopolysaccharide (LPS)-stimulated MMP and TIMP-1 release from cultured microglia and astrocytes. In contrast, however, resveratrol does not inhibit release of MMP-9 from cortical neurons. Overall, these results are consistent with the possibility that while resveratrol reduces potentially maladaptive MMP and TIMP-1 release from activated glia, neuroplasticity-promoting MMP release from neurons is spared. In contrast, resveratrol reduces release of neurocan and brevican, extracellular matrix components that restrict neuroplasticity, from both neurons and glia. These data underscore the diversity of resveratrol's actions with respect to affected cell types and molecular targets and also suggest that further studies may be warranted to determine if its effects on glial MMP release could make it a useful adjunct for AD- and/or anti-amyloid therapy-related damage to the blood brain barrier.

Mathematical Model of Synaptic Long-Term Potentiation as a Bistability in a Chain of Biochemical Reactions with a Positive Feedback.

Nitric oxide (NO) is involved in synaptic long-term potentiation (LTP) by multiple signaling pathways. Here, we show that LTP of synaptic transmission can be explained as a feature of signal transduction-bistable behavior in a chain of biochemical reactions with positive feedback, formed by diffusion of NO to the presynaptic site and facilitating the release of glutamate (Glu). The dynamics of Glu, calcium (Ca2+) and NO is described by a system of nonlinear reaction-diffusion equations with modified Michaelis-Menten (MM) kinetics. Numerical investigation reveals that the chain of biochemical reactions analyzed can exhibit a bistable behavior under physiological conditions when production of Glu is described by MM kinetics and decay of NO is modeled by means of two enzymatic pathways with different kinetic properties. Our finding extends understanding of the role of NO in LTP: a short high-intensity stimulus is "memorized" as a long-lasting elevation of NO concentration. The conclusions obtained by analysis of the chain of biochemical reactions describing LTP can be generalized to other chains of interactions or for creating the logical elements for biological computers.

Zelquistinel Is an Orally Bioavailable Novel NMDA Receptor Allosteric Modulator That Exhibits Rapid and Sustained Antidepressant-Like Effects.

The role of glutamatergic receptors in major depressive disorder continues to be of great interest for therapeutic development. Recent studies suggest that both negative and positive modulation of N-methyl-D-aspartate receptors (NMDAR) can produce rapid antidepressant effects. Here we report that zelquistinel, a novel NMDAR allosteric modulator, exhibits high oral bioavailability and dose-proportional exposures in plasma and the central nervous system and produces rapid and sustained antidepressant-like effects in rodents by enhancing activity-dependent, long-term synaptic plasticity. NMDAR-mediated functional activity was measured in cultured rat brain cortical neurons (calcium imaging), hNR2A or B subtype-expressing HEK cells, and synaptic plasticity in rat hippocampal and medial prefrontal cortex slices in vitro. Pharmacokinetics were evaluated in rats following oral administration. Antidepressant-like effects were assessed in the rat forced swim test and the chronic social deficit mouse model. Target engagement and the safety/tolerability profile was assessed using phencyclidine-induced hyperlocomotion and rotarod rodent models. Following a single oral dose, zelquistinel (0.1-100 µg/kg) produced rapid and sustained antidepressant-like effects in the rodent depression models. Brain/ cerebrospinal fluid concentrations associated with zelquistinel antidepressant-like activity also increased NMDAR function and rapidly and persistently enhanced activity-dependent synaptic plasticity (long-term potentiation), suggesting that zelquistinel produces antidepressant-like effects by enhancing NMDAR function and synaptic plasticity. Furthermore, Zelquistinel inhibited phencyclidine (an NMDAR antagonist)-induced hyperlocomotion and did not impact rotarod performance. Zelquistinel produces rapid and sustained antidepressant effects by positively modulating the NMDARs, thereby enhancing long-term potentiation of synaptic transmission.

Gut dysbiosis impairs hippocampal plasticity and behaviors by remodeling serum metabolome

ABSTRACT Accumulating evidence suggests that gut microbiota as a critical mediator of gut-brain axis plays an important role in human health. Altered gut microbial profiles have been implicated in increasing the vulnerability of psychiatric disorders, such as autism, depression, and schizophrenia. However, the cellular and molecular mechanisms underlying the association remain unknown. Here, we modified the gut microbiome with antibiotics in newborn mice, and found that gut microbial alteration induced behavioral impairment by decreasing adult neurogenesis and long-term potentiation of synaptic transmission, and altering the gene expression profile in hippocampus. Reconstitution with normal gut flora produced therapeutic effects against both adult neurogenesis and behavioral deficits in the dysbiosis mice. Furthermore, our results show that circulating metabolites changes mediate the effect of gut dysbiosis on hippocampal plasticity and behavior outcomes. Elevating the serum 4-methylphenol, a small aromatic metabolite produced by gut bacteria, was found to induce autism spectrum disorder (ASD)-like behavior impairment and hippocampal dysfunction. Together our finding demonstrates that early-life gut dysbiosis and its correlated metabolites change contribute to hippocampal dysfunction and behavior impairment, hence highlight the potential microbiome-mediated therapies for treating psychiatric disorders.

Effect of oral administration of Magnesium N-Acetyltaurinate on synaptic plasticity in rodents.

While magnesium deficiency is common and its effects well known on the nervous system, very few studies has been dedicated to the efficiency of magnesium replacement treatments on the central nervous system. In this study, the effects of oral administration of magnesium salts of acetyl-taurinate on the central manifestations of magnesium deficiency is described in rats submitted to low-magnesium diet and in a murine model of Alzheimer's disease. We tested the effect of ATA Mg®, a salt combining magnesium and taurine, on the hippocampus, a critical component of cognition. 7-10-month-old rats were submitted to dietary magnesium deprivation for 64 days. The effect of magnesium deficiency was studied in ex vivo hippocampal slices. We showed that long-term potentiation of synaptic transmission in the hippocampus was significantly improved by the oral administration of ATA Mg® at a dose of 50 mg/kg bw/day, which is comparable to the recommended dose in humans. 7-10-months-old transgenic APP/PS1 mice, a model of Alzheimer's disease, received ATA Mg® during 24 days at a dose of 700 mg/kg bw/day which is the dose used in previous studies demonstrating the positive effect of magnesium supplementation. We showed that long-term potentiation was significantly improved in the treated mice. Moreover, the expression of NR2B subunit of NMDA receptors, known to be involved in synaptic plasticity, was significantly increased in the hippocampus. These results demonstrate the ability of ATA Mg® to improve the symptoms related to chronic magnesium deficiency at the level of the hippocampus suggesting its bioavailability and effectiveness in reaching the central nervous system.

A Study of Synaptic Plasticity in the Rat Hippocampal Field CA1 in Conditions of Deficiency of Acetylcholine and Other Neurotransmitters

Experiments showed that high-amplitude, long-lasting tetanic potentiation could be induced in synaptic terminals formed by Schaffer collaterals on field CA1 pyramidal cells in rat hippocampal slices in which acetylcholine deficiency was modeled by application of the choline reuptake inhibitor hemicholine and the vesicular acetylcholine uptake inhibitor vesamicol. Deficiencies of different neurotransmitters were modeled by 5-min incubation of slices in solution containing an elevated potassium concentration, which led, as demonstrated previously, to depletion of the release of these neurotransmitters from nerve endings. The result of this procedure was that synapses formed by Schaffer collaterals developed long-term potentiation. Long-term post-tetanic potentiation was also induced in slices on this background in the model of neurotransmitter deficiency. Its amplitude was not significantly different from the amplitude of long-term potentiation in controls but was less than that obtained using vesamicol or hemicholine. As deficiency of serotonin, noradrenaline, and dopamine is known to be able to decrease the extent of long-term potentiation of synaptic transmission between fields CA3 and CA1, these result points to the possibility that acetylcholine deficiency partially compensates for this decrease. Considering known data on the locations of different types of nicotinic and muscarinic cholinoreceptors both on pyramidal cells and on inhibitory interneurons, the possible effects of acetylcholine on the efficiency of the inputs formed by Schaffer collaterals were studied. This analysis and consideration of the data obtained here led to the hypothesis that in conditions of acetylcholine deficiency, the main influence on the efficiency of excitation of pyramidal cells in field CA1 by field CA3 is exerted by disinhibition via a network of interacting interneurons.

Assessing the Quality and Potential Efficacy of Commercial Extracts of Rhodiola rosea L. by Analyzing the Salidroside and Rosavin Content and the Electrophysiological Activity in Hippocampal Long-Term Potentiation, a Synaptic Model of Memory.

Rhodiola rosea L. roots and rhizome extracts are active ingredients in adaptogenic herbal medicinal products (HMP) and dietary supplements for temporary relief of symptoms of stress, such as fatigue and weakness. R. rosea extract has a stimulating effect on the CNS, suggesting potential benefits on cognitive functions, memory, learning, and attention. The reproducible efficacy and quality of preparations of the underground parts of R. rosea depend on the highly variable content of the active markers, salidroside and rosavin, which affect the quality of HMP and dietary supplements. However, it is not clear which analytical markers are important for assessing the efficacy of R. rosea preparations intended for use in aging-induced mild cognitive disorders, such as attenuated memory, attention, and learning. Furthermore, the activity of various commercial R. rosea extracts has not been correlated with their content. Here, the biological activities of salidroside, rosavin, and seven commercial extracts of underground parts of R. rosea were assessed using a synaptic model of memory: long-term potentiation (LTP) of synaptic transmission in hippocampus slices. A high degree of variation in the content of all active markers was observed. One extract from China lacked rosavin, and there was even variation in the extracts from the Altai geographic region. In vitro, rosavin, salidroside and all tested R. rosea extracts potentiated electric stimulation of an intra-hippocampal electric circuit, which resulted in higher responses of the pyramidal cells in isolated hippocampus slices. Rosavin was more active at higher concentrations than salidroside; while, salidroside was more effective at lower concentrations. The highest content of both active markers was found in the extracts that were active at the lowest concentrations tested; while, some extracts contained some other compounds that presumably reduced the efficacy due to antagonistic interactions. Standardized content of active markers is necessary for the quality control of herbal preparations containing R. rosea extracts, but insufficient for assessment of their potential efficacy. Additional bioassays are needed to assure the reproducible pharmacological activity of R. rosea extracts; therefore, the LTP of synaptic transmission in hippocampus slices may serve as a validation tool for the quality control of R. rosea extracts.

Advances in Acupuncture Mechanism Research on the Changes of Synaptic Plasticity: "Pain Memory" for Chronic Pain

Previous studies have shown that there are many common structures between the neural network of pain and memory, and the main structure in the pain network is also part of the memory network. Chronic pain is characterized by recurrent attacks and is associated with persistent ectopic impulse, which causes changes in synaptic structure and function based on nerve activity. These changes may induce long-term potentiation of synaptic transmission, and ultimately lead to changes in the central nervous system to produce "pain memory". Acupuncture is an effective method in treating chronic pain. It has been proven that acupuncture can affect the spinal cord dorsal horn, hippocampus, cingulate gyrus and other related areas. The possible mechanisms of action include opioid-induced analgesia, activation of glial cells, and the expression of brain derived neurotrophic factor (BDNF). In this study, we systematically review the brain structures, stage of "pain memory" and the mechanisms of acupuncture on synaptic plasticity in chronic pain.

Dual Influence of Endocannabinoids on Long-Term Potentiation of Synaptic Transmission.

Cannabinoid receptor 1 (CB1R) is widely distributed in the central nervous system, in excitatory and inhibitory neurons, and in astrocytes. CB1R agonists impair cognition and prevent long-term potentiation (LTP) of synaptic transmission, but the influence of endogenously formed cannabinoids (eCBs) on hippocampal LTP remains ambiguous. Based on the knowledge that eCBs are released upon high frequency neuronal firing, we hypothesized that the influence of eCBs upon LTP could change according to the paradigm of LTP induction. We thus tested the influence of eCBs on hippocampal LTP using two θ-burst protocols that induce either a weak or a strong LTP. LTP induced by a weak-θ-burst protocol is facilitated while preventing the endogenous activation of CB1Rs. In contrast, the same procedures lead to inhibition of LTP induced by the strong-θ-burst protocol, suggestive of a facilitatory action of eCBs upon strong LTP. Accordingly, an inhibitor of the metabolism of the predominant eCB in the hippocampus, 2-arachidonoyl-glycerol (2-AG), facilitates strong LTP. The facilitatory action of endogenous CB1R activation does not require the activity of inhibitory A1 adenosine receptors, is not affected by inhibition of astrocytic metabolism, but involves inhibitory GABAergic transmission. The continuous activation of CB1Rs via exogenous cannabinoids, or by drugs known to prevent metabolism of the non-prevalent hippocampal eCB, anandamide, inhibited LTP. We conclude that endogenous activation of CB1Rs by physiologically formed eCBs exerts a fine-tune homeostatic control of LTP in the hippocampus, acting as a high-pass filter, therefore likely reducing the signal-to-noise ratio of synaptic strengthening.

Endocannabinoid-Dependent Long-Term Potentiation of Synaptic Transmission at Rat Barrel Cortex.

Brain-derived neurotrophic factor (BDNF) plays a critical role in modulating plasticity in sensory cortices. Indeed, a BDNF-dependent long-term potentiation (LTP) at distal basal excitatory synapses of Layer 5 pyramidal neurons (L5PNs) has been demonstrated in disinhibited rat barrel cortex slices. Although it is well established that this LTP requires the pairing of excitatory postsynaptic potentials (PSPs) with Ca2+ spikes, its induction when synaptic inhibition is working remains unexplored. Here we show that low-frequency stimulation at basal dendrites of L5PNs is able to trigger a PSP followed by an action potential (AP) and a slow depolarization (termed PSP-Ca2+ response) in thalamocortical slices without blocking synaptic inhibition. We demonstrate that AP barrage-mediated release of endocannabinoids (eCBs) from the recorded L5PNs induces PSP-Ca2+ response facilitation and BDNF-dependent LTP. Indeed, this LTP requires the type 1 cannabinoid receptors activation, is prevented by postsynaptic intracellular 1,2-bis(2-aminophenoxy) ethane-N,N,N,N'-tetraacetic acid (BAPTA) or the anandamide membrane transporter inhibitor AM404, and only occurs in L5PNs neurons showing depolarization-induced suppression of inhibition. Additionally, electrical stimulation at the posteromedial thalamic nucleus induced similar response and LTP. These results reveal a novel form of eCB-dependent LTP at L5PNs that could be relevant in the processing of sensory information in the barrel cortex.

Ketamine Metabolites Enantioselectively Decrease Intracellular D-Serine Concentrations in PC-12 Cells.

D-Serine is an endogenous NMDA receptor co-agonist that activates synaptic NMDA receptors modulating neuronal networks in the cerebral cortex and plays a key role in long-term potentiation of synaptic transmission. D-serine is associated with NMDA receptor neurotoxicity and neurodegeneration and elevated D-serine concentrations have been associated with Alzheimer’s and Parkinsons’ diseases and amyotrophic lateral sclerosis. Previous studies have demonstrated that the ketamine metabolites (rac)-dehydronorketamine and (2S,6S)-hydroxynorketamine decrease intracellular D-serine concentrations in a concentration dependent manner in PC-12 cells. In the current study, PC-12 cells were incubated with a series of ketamine metabolites and the IC50 values associated with attenuated intracellular D-serine concentrations were determined. The results demonstrate that structural and stereochemical features of the studied compounds contribute to the magnitude of the inhibitory effect with (2S,6S)-hydroxynorketamine and (2R,6R)-hydroxynorketamine displaying the most potent inhibition with IC50 values of 0.18 ± 0.04 nM and 0.68 ± 0.09 nM. The data was utilized to construct a preliminary 3D-QSAR/pharmacophore model for use in the design of new and more efficient modulators of D-serine.

Effect of Neonatal Seizures on the Synaptic Plasticity of Rat Somatosensory Cortex

Using an experimental model of neonatal recurrent seizures, we investigated the influence of epileptic seizures on the various forms of synaptic plasticity in neurons of the somatosensory cortex. We have found that early seizures do not affect the post-tetanic potentiation of the amplitude of the postsynaptic potentials and the depression of postsynaptic potentials during high-frequency stimulation. However, they result in the chronic increase in the long-term potentiation of synaptic transmission. The changes in synaptic plasticity may affect the processing of the sensory information in patients with a history of recurrent seizures during early development.

Neurophysiology of Aggression in Posttraumatic Stress Disorder

Posttraumatic stress disorder (PTSD) is a universal anxiety disorder, affecting not only soldiers but also victims of every sort of traumatic stress-natural disaster, automobile collision, crime, domestic violence, bereavement. Aggressiveness, stemming from “intermittent explosive anger”, is a not infrequent comorbidity of PTSD, with the most serious consequences. The neurophysiology of aggression and anger in general, and PTSD in particular, is a jigsaw puzzle of which we are first gathering the pieces. In this chapter, PTSD is conceptualized as revolving around an idee fix of the traumatic experience, leading to fear and a derivative defensive form of aggression. The history of research in the neurophysiology of aggression and pertinent forms of memory and emotion are then reviewed, leading to a neuronal system that spans the brain. Some basic phenomena in neurophysiology are touched onsynaptic plasticity in the form of long-term potentiation of synaptic transmission, G-protein–coupled receptor modulation thereof, and the theta rhythm of the electroencephalogram-and the path we are following in our attempt to integrate these phenomena into a model of the neurophysiology of aggression in PTSD is described.

EFFECT OF NEONATAL SEIZURES ON THE SYNAPTIC PLASTICITY OF RAT SOMATOSENSORY CORTEX

Using an experimental model of neonatal recurrent seizures we investigated the influence of epileptic seizures in the various forms of synaptic plasticity in neurons of the somatosensory cortex. We found that early seizures do not affect the post-tetanic potentiation of the amplitude of the postsynaptic potentials and the depression of postsynaptic potentials during high-frequency stimulation. However they result in the chronic increase of the long-term potentiation of synaptic transmission. These changes of synaptic plasticity may affect the processing of the sensory information in patients with a history of recurrent seizures during early development.

Neuraminidase inhibition primes short-term depression and suppresses long-term potentiation of synaptic transmission in the rat hippocampus.

Neuraminidase (NEU) is a key enzyme that cleaves negatively charged sialic acid residues from membrane proteins and lipids. Clinical and basic science studies have shown that an imbalance in NEU metabolism or changes in NEU activity due to various pathological conditions parallel with behavior and cognitive impairment. It has been suggested that the decreases of NEU activity could cause serious neurological consequences. However, there is a lack of direct evidences that modulation of endogenous NEU activity can impair neuronal function. Using combined rat entorhinal cortex/hippocampal slices and a specific inhibitor of NEU, 2-deoxy-2,3-dehydro-N-acetylneuraminic acid (NADNA), we examined the effect of downregulation of NEU activity on different forms of synaptic plasticity in the hippocampal CA3-to-CA1 network. We show that NEU inhibition results in a significant decrease in long-term potentiation (LTP) and an increase in short-term depression. Synaptic depotentiation restores LTP in NADNA-pretreated slices to the control level. These data suggest that short-term NEU inhibition produces the LTP-like effect on neuronal network, which results in damping of further LTP induction. Our findings demonstrate that downregulation of NEU activity could have a major impact on synaptic plasticity and provide a new insight into the cellular mechanism underlying behavioral and cognitive impairment associated with abnormal metabolism of NEU.

LY293558 prevents soman-induced pathophysiological alterations in the basolateral amygdala and the development of anxiety

Exposure to nerve agents can cause brain damage due to prolonged seizure activity, producing long-term behavioral deficits. We have previously shown that LY293558, a GluK1/AMPA receptor antagonist, is a very effective anticonvulsant and neuroprotectant against nerve agent exposure. In the present study, we examined whether the protection against nerve agent-induced seizures and neuropathology conferred by LY293558 translates into protection against pathophysiological alterations in the basolateral amygdala (BLA) and the development of anxiety, which is the most prevalent behavioral deficit resulting from exposure. LY293558 (15 mg/kg) was administered to rats, along with atropine and HI-6, at 20 min after exposure to soman (1.2 × LD50). At 24 h, 7 days, and 30 days after exposure, soman-exposed rats who did not receive LY293558 had reduced but prolonged evoked field potentials in the BLA, as well as increased paired-pulse ratio, suggesting neuronal damage and impaired synaptic inhibition; rats who received LY293558 did not differ from controls in these parameters. Long-term potentiation of synaptic transmission was impaired at 7 days after exposure in the soman-exposed rats who did not receive anticonvulsant treatment, but not in the LY293558-treated rats. Anxiety-like behavior assessed by the open field and acoustic startle response tests was increased in the soman-exposed rats at 30 and 90 days after exposure, while rats treated with LY293558 did not differ from controls. Along with our previous findings, the present data demonstrate the remarkable efficacy of LY293558 in counteracting nerve agent-induced seizures, neuropathology, pathophysiological alterations in the BLA, and anxiety-related behavioral deficits.

NMDA receptor-dependent LTD is required for consolidation but not acquisition of fear memory.

NMDA receptor-dependent long-term depression (NMDAR-LTD) is a form of synaptic plasticity leading to long-lasting decreases in synaptic strength. NMDAR-LTD is essential for spatial and working memory, but its role in hippocampus-dependent fear memory has yet to be determined. Induction of NMDAR-LTD requires the activation of caspase-3 by cytochrome c. Cytochrome c normally resides in mitochondria and during NMDAR-LTD is released from mitochondria, a process promoted by Bax (Bcl-2-associated X protein). Bax induces cell death in apoptosis, but it plays a nonapoptotic role in NMDAR-LTD. Here, we investigated the role of NMDAR-LTD in fear memory in CA1-specific Bax knock-out mice. In hippocampal slices from these knock-out mice, while long-term potentiation of synaptic transmission, basal synaptic transmission, and paired-pulse ratio are intact, LTD in both young and fear-conditioned adult mice is obliterated. Interestingly, in CA1-specific Bax knock-out mice, long-term contextual fear memory is impaired, but the acquisition of fear memory and innate fear are normal. Moreover, these conditional Bax knock-out mice exhibit less behavioral despair. These findings indicate that NMDAR-LTD is required for consolidation, but not the acquisition of fear memory. Our study also shows that Bax plays an important role in depressive behavior.

Intraneuronal accumulation of Aβ42 induces age-dependent slowing of neuronal transmission in Drosophila.

Beta amyloid (Aβ42)-induced dysfunction and loss of synapses are believed to be major underlying mechanisms for the progressive loss of learning and memory abilities in Alzheimer's disease (AD). The vast majority of investigations on AD-related synaptic impairment focus on synaptic plasticity, especially the decline of long-term potentiation of synaptic transmission caused by extracellular Aβ42. Changes in other aspects of synaptic and neuronal functions are less studied or undiscovered. Here, we report that intraneuronal accumulation of Aβ42 induced an age-dependent slowing of neuronal transmission along pathways involving multiple synapses.

Targeted deletion of the C-terminus of the mouse adenomatous polyposis coli tumor suppressor results in neurologic phenotypes related to schizophrenia

BackgroundLoss of adenomatous polyposis coli (APC) gene function results in constitutive activation of the canonical Wnt pathway and represents the main initiating and rate-limiting event in colorectal tumorigenesis. APC is likely to participate in a wide spectrum of biological functions via its different functional domains and is abundantly expressed in the brain as well as in peripheral tissues. However, the neuronal function of APC is poorly understood. To investigate the functional role of Apc in the central nervous system, we analyzed the neurological phenotypes of Apc1638T/1638T mice, which carry a targeted deletion of the 3′ terminal third of Apc that does not affect Wnt signaling.ResultsA series of behavioral tests revealed a working memory deficit, increased locomotor activity, reduced anxiety-related behavior, and mildly decreased social interaction in Apc1638T/1638T mice. Apc1638T/1638T mice showed abnormal morphology of the dendritic spines and impaired long-term potentiation of synaptic transmission in the hippocampal CA1 region. Moreover, Apc1638T/1638T mice showed abnormal dopamine and serotonin distribution in the brain. Some of these behavioral and neuronal phenotypes are related to symptoms and endophenotypes of schizophrenia.ConclusionsOur results demonstrate that the C-terminus of the Apc tumor suppressor plays a critical role in cognitive and neuropsychiatric functioning. This finding suggests a potential functional link between the C-terminus of APC and pathologies of the central nervous system.

BDNF: a regulator of learning and memory processes with clinical potential

Memories are believed to be represented by facilitated synaptic transmission of electrical signals in neuronal networks. The ability to acquire new memories or to change old memory content results from the plastic properties of the brain. Molecular changes in synaptic plasticity of neuronal networks are considered to be the cellular correlates of learning and memory, and the neurotrophin brain-derived neurotropic factor (BDNF) plays an important role in these processes. This neurotrophic factor coordinates a multitude of biological functions. In addition to its role in neuronal plasticity processes, such as long-term potentiation of synaptic transmission, the protein regulates the differentiation of neuronal precursor cells, synaptogenesis, and neuronal survival. Cellular processes like BDNF protein processing, anterograde and retrograde transport, as well as exocytosis and endocytosis of BDNF vesicles are necessary to enable the protein to fulfill its neuroprotective and plasticity-related functions in its target areas. Therefore, deficits in one of these functions, resulting in a reduction or a lack of BDNF supply, can result in dysfunctional or reduced synaptic plasticity in virtually every brain area. Since cognitive processes and mental health require the intact formation and modification of memory traces, a change in BDNF turnover is considered as a contributing factor to a number of neurodegenerative and psychological disorders. This review summarizes the current knowledge regarding the connection between BDNF, its role in synaptic plasticity and its role in brain.