Cyclic AMP-dependent protein kinase and D1 dopamine receptors regulate diacylglycerol lipase-α and synaptic 2-arachidonoyl glycerol signaling.

Brain endocannabinoids serve as retrograde neurotransmitters, being synthesized in post-synaptic neurons "on demand" and released to bind pre-synaptic cannabinoid receptors and suppress glutamatergic or GABAergic transmission. The most abundant brain endocannabinoid, 2 arachidonoyl glycerol (2-AG), is primarily synthesized by diacylglycerol lipase-α (DGLα), which is activated by poorly understood mechanisms in response to calcium influx following post-synaptic depolarization and/or the activation of Gq -coupled group 1 metabotropic glutamate receptors. However, the impact of other neurotransmitters and their downstream signaling pathways on synaptic 2-AG signaling has not been intensively studied. Here, we found that DGLα activity in membrane fractions from transfected HEK293T cells was significantly increased by in vitro phosphorylation using cyclic AMP-dependent protein kinase (PKA). Moreover, PKA directly phosphorylated DGLα at Ser798 in vitro. Elevation of cAMP levels in HEK293 cells expressing DGLα increased Ser798 phosphorylation, as detected using a phospho-Ser798-specific antibody, and enhanced DGLα activity; this in situ enhancement of DGLα activity was prevented by mutation of Ser798 to Ala. We investigated the impact of PKA on synaptic 2-AG mobilization in mouse striatal slices by manipulating D1-dopamine receptor (D1R) signaling and assessing depolarization-induced suppression of excitation, a DGLα- and 2-AG-dependent form of short-term synaptic depression. The magnitude of depolarization-enhanced suppression of excitation in direct pathway medium spiny neurons was increased by pre-incubation with a D1R agonist, and this enhancement was blocked by post-synaptic inhibition of PKA. Taken together, these findings provide new molecular insights into the complex mechanisms regulating synaptic endocannabinoid signaling.

Screening, Brief Intervention, and Referral to Treatment in a Retail Pharmacy Setting: The Pharmacist's Role in Identifying and Addressing Risk of Substance Use Disorder.

OBJECTIVE: This study determined the feasibility of interviewing and screening patients presenting to a retail pharmacy using Screening, Brief Intervention, and Referral to Treatment (SBIRT) interview protocols, and to compare SBIRT results to a risk score calculated from Prescription Drug Monitoring Program (PDMP) data. METHODS: Using the NIDA Quick Screen and NIDA Modified-ASSIST (NM-ASSIST) and the Alcohol Use Disorder Identification Test (AUDIT), retail pharmacy customers were screened for substance and alcohol use disorder and tobacco use. PDMP reports were collected on subjects and a PDMP-risk score was calculated based on the numbers of Schedule II-V prescriptions and prescribers over the previous 12 months. RESULTS: A total of 24 patients were included in this study (67% response rate). SBIRT screening revealed that 20.8% were at-risk for substance use disorder (SUD), 16.7% for alcohol use disorder, and 37.5% used tobacco. Overall, 33.3% of subjects were at-risk for SUD or alcohol use disorder. Fifty percent of subjects required education and/or brief intervention based on their responses, 37.5% of all subjects were deemed at-risk based on their PDMP-risk score, and 60% of patients who were risk-positive by SBIRT screening were also PDMP-risk positive. CONCLUSIONS: This study demonstrates the feasibility of performing SBIRT-based screenings in a retail pharmacy setting and combining these with PDMP-risk analysis to screen patients for prescription and illicit drug misuse. Findings from this study will inform the design of larger multisite studies, which should validate these findings and include follow-up analysis to assess the efficacy of intervention on this patient population.

Activated CaMKIIα Binds to the mGlu5 Metabotropic Glutamate Receptor and Modulates Calcium Mobilization.

Ca2+/calmodulin-dependent protein kinase II (CaMKII) and metabotropic glutamate receptor 5 (mGlu5) are critical signaling molecules in synaptic plasticity and learning/memory. Here, we demonstrate that mGlu5 is present in CaMKIIα complexes isolated from mouse forebrain. Further in vitro characterization showed that the membrane-proximal region of the C-terminal domain (CTD) of mGlu5a directly interacts with purified Thr286-autophosphorylated (activated) CaMKIIα However, the binding of CaMKIIα to this CTD fragment is reduced by the addition of excess Ca2+/calmodulin or by additional CaMKIIα autophosphorylation at non-Thr286 sites. Furthermore, in vitro binding of CaMKIIα is dependent on a tribasic residue motif Lys-Arg-Arg (KRR) at residues 866-868 of the mGlu5a-CTD, and mutation of this motif decreases the coimmunoprecipitation of CaMKIIα with full-length mGlu5a expressed in heterologous cells by about 50%. The KRR motif is required for two novel functional effects of coexpressing constitutively active CaMKIIα with mGlu5a in heterologous cells. First, cell-surface biotinylation studies showed that CaMKIIα increases the surface expression of mGlu5a Second, using Ca2+ fluorimetry and single-cell Ca2+ imaging, we found that CaMKIIα reduces the initial peak of mGlu5a-mediated Ca2+ mobilization by about 25% while doubling the relative duration of the Ca2+ signal. These findings provide new insights into the physical and functional coupling of these key regulators of postsynaptic signaling.

Role of Striatal Direct Pathway 2-Arachidonoylglycerol Signaling in Sociability and Repetitive Behavior.

BACKGROUND: Endocannabinoid signaling plays an important role in regulating synaptic transmission in the striatum, a brain region implicated as a central node of dysfunction in autism spectrum disorder. Deficits in signaling mediated by the endocannabinoid 2-arachidonoylglycerol (2-AG) have been reported in mouse models of autism spectrum disorder, but a causal role for striatal 2-AG deficiency in phenotypes relevant to autism spectrum disorder has not been explored. METHODS: Using conditional knockout mice, we examined the electrophysiological, biochemical, and behavioral effects of 2-AG deficiency by deleting its primary synthetic enzyme, diacylglycerol lipase α (DGLα), from dopamine D1 receptor-expressing or adenosine A2a receptor-expressing medium spiny neurons (MSNs) to determine the role of 2-AG signaling in striatal direct or indirect pathways, respectively. We then used viral-mediated deletion of DGLα to study the effects of 2-AG deficiency in the ventral and dorsal striatum. RESULTS: Targeted deletion of DGLα from direct-pathway MSNs caused deficits in social interaction, excessive grooming, and decreased exploration of a novel environment. In contrast, deletion from indirect-pathway MSNs had no effect on any measure of behavior examined. Loss of 2-AG in direct-pathway MSNs also led to increased glutamatergic drive, which is consistent with a loss of retrograde feedback inhibition. Subregional DGLα deletion from the dorsal striatum produced deficits in social interaction, whereas deletion from the ventral striatum resulted in repetitive grooming. CONCLUSIONS: These data suggest a role for 2-AG deficiency in social deficits and repetitive behavior, and they demonstrate a key role for 2-AG in regulating striatal direct-pathway MSNs.

Endocannabinoid signalling modulates susceptibility to traumatic stress exposure.

Stress is a ubiquitous risk factor for the exacerbation and development of affective disorders including major depression and posttraumatic stress disorder. Understanding the neurobiological mechanisms conferring resilience to the adverse consequences of stress could have broad implications for the treatment and prevention of mood and anxiety disorders. We utilize laboratory mice and their innate inter-individual differences in stress-susceptibility to demonstrate a critical role for the endogenous cannabinoid 2-arachidonoylglycerol (2-AG) in stress-resilience. Specifically, systemic 2-AG augmentation is associated with a stress-resilient phenotype and enhances resilience in previously susceptible mice, while systemic 2-AG depletion or CB1 receptor blockade increases susceptibility in previously resilient mice. Moreover, stress-resilience is associated with increased phasic 2-AG-mediated synaptic suppression at ventral hippocampal-amygdala glutamatergic synapses and amygdala-specific 2-AG depletion impairs successful adaptation to repeated stress. These data indicate amygdala 2-AG signalling mechanisms promote resilience to adverse effects of acute traumatic stress and facilitate adaptation to repeated stress exposure.

A Novel Human CAMK2A Mutation Disrupts Dendritic Morphology and Synaptic Transmission, and Causes ASD-Related Behaviors.

Characterizing the functional impact of novel mutations linked to autism spectrum disorder (ASD) provides a deeper mechanistic understanding of the underlying pathophysiological mechanisms. Here we show that a de novo Glu183 to Val (E183V) mutation in the CaMKIIα catalytic domain, identified in a proband diagnosed with ASD, decreases both CaMKIIα substrate phosphorylation and regulatory autophosphorylation, and that the mutated kinase acts in a dominant-negative manner to reduce CaMKIIα-WT autophosphorylation. The E183V mutation also reduces CaMKIIα binding to established ASD-linked proteins, such as Shank3 and subunits of l-type calcium channels and NMDA receptors, and increases CaMKIIα turnover in intact cells. In cultured neurons, the E183V mutation reduces CaMKIIα targeting to dendritic spines. Moreover, neuronal expression of CaMKIIα-E183V increases dendritic arborization and decreases both dendritic spine density and excitatory synaptic transmission. Mice with a knock-in CaMKIIα-E183V mutation have lower total forebrain CaMKIIα levels, with reduced targeting to synaptic subcellular fractions. The CaMKIIα-E183V mice also display aberrant behavioral phenotypes, including hyperactivity, social interaction deficits, and increased repetitive behaviors. Together, these data suggest that CaMKIIα plays a previously unappreciated role in ASD-related synaptic and behavioral phenotypes.SIGNIFICANCE STATEMENT Many autism spectrum disorder (ASD)-linked mutations disrupt the function of synaptic proteins, but no single gene accounts for >1% of total ASD cases. The molecular networks and mechanisms that couple the primary deficits caused by these individual mutations to core behavioral symptoms of ASD remain poorly understood. Here, we provide the first characterization of a mutation in the gene encoding CaMKIIα linked to a specific neuropsychiatric disorder. Our findings demonstrate that this ASD-linked de novo CAMK2A mutation disrupts multiple CaMKII functions, induces synaptic deficits, and causes ASD-related behavioral alterations, providing novel insights into the synaptic mechanisms contributing to ASD.

Quantitative proteomics analysis of CaMKII phosphorylation and the CaMKII interactome in the mouse forebrain.

Ca(2+)/calmodulin-dependent protein kinase IIα (CaMKIIα) autophosphorylation at Thr286 and Thr305/Thr306 regulates kinase activity and modulates subcellular targeting and is critical for normal synaptic plasticity and learning and memory. Here, a mass spectrometry-based approach was used to identify Ca(2+)-dependent and -independent in vitro autophosphorylation sites in recombinant CaMKIIα and CaMKIIß. CaMKII holoenzymes were then immunoprecipitated from subcellular fractions of forebrains isolated from either wild-type (WT) mice or mice with a Thr286 to Ala knock-in mutation of CaMKIIα (T286A-KI mice) and analyzed using the same approach in order to characterize in vivo phosphorylation sites in both CaMKII isoforms and identify CaMKII-associated proteins (CaMKAPs). A total of six and seven autophosphorylation sites in CaMKIIα and CaMKIIß, respectively, were detected in WT mice. Thr286-phosphorylated CaMKIIα and Thr287-phosphorylated CaMKIIß were selectively enriched in WT Triton-insoluble (synaptic) fractions compared to Triton-soluble (membrane) and cytosolic fractions. In contrast, Thr306-phosphorylated CaMKIIα and Ser315- and Thr320/Thr321-phosphorylated CaMKIIß were selectively enriched in WT cytosolic fractions. The T286A-KI mutation significantly reduced levels of phosphorylation of CaMKIIα at Ser275 across all subcellular fractions and of cytosolic CaMKIIß at Ser315 and Thr320/Thr321. Significantly more CaMKAPs coprecipitated with WT CaMKII holoenzymes in the synaptic fraction compared to that in the membrane fraction, with functions including scaffolding, microtubule organization, actin organization, ribosomal function, vesicle trafficking, and others. The T286A-KI mutation altered the interactions of multiple CaMKAPs with CaMKII, including several proteins linked to autism spectrum disorders. These data identify CaMKII isoform phosphorylation sites and a network of synaptic protein interactions that are sensitive to the abrogation of Thr286 autophosphorylation of CaMKIIα, likely contributing to the diverse synaptic and behavioral deficits of T286A-KI mice.

The initiation of synaptic 2-AG mobilization requires both an increased supply of diacylglycerol precursor and increased postsynaptic calcium.

On-demand postsynaptic synthesis and release of endocannabinoid lipids and subsequent binding to presynaptic CB1 receptors (CB1Rs) mediates short and long-term depression (LTD) of excitatory transmission in many brain regions. However, mechanisms involved in the synthesis of the endocannabinoid 2-arachidonoylglycerol (2-AG) by diacylglycerol lipase α (DGLα) are poorly understood. Since Gq-coupled receptor activation can stimulate production of a major DGL substrate 1-stearoyl-2-arachidonoyl-sn-glycerol (SAG) by PLCß, we sought to determine if 2-AG biosynthesis was limited only by a lack of substrate availability, or if other pathways, such as Ca(2+) signaling, also need to be simultaneously engaged. To address this question, we loaded medium spiny neurons of the dorsolateral striatum with SAG while monitoring excitatory synaptic inputs. SAG-loading had no significant effect on evoked excitatory synaptic currents when cells were voltage-clamped at -80 mV. However, depolarization of MSNs to -50 mV revealed a SAG-loading dependent decrease in the amplitude of excitatory currents that was accompanied by an increase in paired pulse ratio, consistent with decreased glutamate release. Both effects of loading SAG at -50 mV were blocked by chelation of postsynaptic Ca(2+) using BAPTA or by bath application of tetrahydrolipstatin (THL), a DGL inhibitor. Loading of SAG into glutamatergic pyramidal neurons of the amygdala similarly inhibited excitatory synaptic inputs and increased the PPR. SAG-induced depression was absent in both regions from mice lacking CB1Rs. These data show that increasing substrate availability alone is insufficient to drive 2-AG mobilization and that DGL-dependent synaptic depression via CB1R activation requires postsynaptic Ca(2+) signals.

Genetic disruption of 2-arachidonoylglycerol synthesis reveals a key role for endocannabinoid signaling in anxiety modulation.

Endocannabinoid (eCB) signaling has been heavily implicated in the modulation of anxiety and depressive behaviors and emotional learning. However, the role of the most-abundant endocannabinoid 2-arachidonoylglycerol (2-AG) in the physiological regulation of affective behaviors is not well understood. Here, we show that genetic deletion of the 2-AG synthetic enzyme diacylglycerol lipase α (DAGLα) in mice reduces brain, but not circulating, 2-AG levels. DAGLα deletion also results in anxiety-like and sex-specific anhedonic phenotypes associated with impaired activity-dependent eCB retrograde signaling at amygdala glutamatergic synapses. Importantly, acute pharmacological normalization of 2-AG levels reverses both phenotypes of DAGLα-deficient mice. These data suggest 2-AG deficiency could contribute to the pathogenesis of affective disorders and that pharmacological normalization of 2-AG signaling could represent an approach for the treatment of mood and anxiety disorders.

CaMKII: a molecular substrate for synaptic plasticity and memory.

Learning and memory is widely believed to result from changes in connectivity within neuronal circuits due to synaptic plasticity. Work over the past two decades has shown that Ca(2+) influx during LTP induction triggers the activation of CaMKII in dendritic spines. CaMKII activation results in autophosphorylation of the kinase rendering it constitutively active long after the Ca(2+) dissipates within the spine. This "molecular switch"(1) mechanism is essential for LTP and learning and memory. Here, we discuss this key regulatory mechanism and the diversity of downstream targets that can be modulated by CaMKII to exert dynamic control of synaptic structure and function.

Substrate-selective COX-2 inhibition decreases anxiety via endocannabinoid activation.

Augmentation of endogenous cannabinoid (eCB) signaling represents an emerging approach to the treatment of affective disorders. Cyclooxygenase-2 (COX-2) oxygenates arachidonic acid to form prostaglandins, but also inactivates eCBs in vitro. However, the viability of COX-2 as a therapeutic target for in vivo eCB augmentation has not been explored. Using medicinal chemistry and in vivo analytical and behavioral pharmacological approaches, we found that COX-2 is important for the regulation of eCB levels in vivo. We used a pharmacological strategy involving substrate-selective inhibition of COX-2 to augment eCB signaling without affecting related non-eCB lipids or prostaglandin synthesis. Behaviorally, substrate-selective inhibition of COX-2 reduced anxiety-like behaviors in mice via increased eCB signaling. Our data suggest a key role for COX-2 in the regulation of eCB signaling and indicate that substrate-selective pharmacology represents a viable approach for eCB augmentation with broad therapeutic potential.

CaMKII regulates diacylglycerol lipase-α and striatal endocannabinoid signaling.

The endocannabinoid 2-arachidonoylglycerol (2-AG) mediates activity-dependent depression of excitatory neurotransmission at central synapses, but the molecular regulation of 2-AG synthesis is not well understood. Here we identify a functional interaction between the 2-AG synthetic enzyme diacylglycerol lipase-α (DGLα) and calcium/calmodulin dependent protein kinase II (CaMKII). Activated CaMKII interacted with the C-terminal domain of DGLα, phosphorylated two serine residues and inhibited DGLα activity. Consistent with an inhibitory role for CaMKII in 2-AG synthesis, in vivo genetic inhibition of CaMKII increased striatal DGL activity and basal levels of 2-AG, and CaMKII inhibition augmented short-term retrograde endocannabinoid signaling at striatal glutamatergic synapses. Lastly, blockade of 2-AG breakdown using concentrations of JZL-184 that have no effect in wild-type mice produced a hypolocomotor response in mice with reduced CaMKII activity. These findings provide mechanistic insights into the molecular regulation of striatal endocannabinoid signaling with implications for physiological control of motor function.

Central insulin resistance and synaptic dysfunction in intracerebroventricular-streptozotocin injected rodents.

To better understand the role of insulin signaling in the development of Alzheimer's disease (AD), we utilized an animal model (intracerebroventricular injection of streptozotocin-ic-streptozotocin (STZ)) that displays insulin resistance only in the brain and exhibits AD pathology. In this model, deficits in hippocampal synaptic transmission and long-term potentiation (LTP) were observed. The decline in LTP correlated with decreased expression of NMDAR subunits NR2A and NR2B. The deficits in LTP were accompanied by changes in the expression and function of synaptic AMPARs. In ic-STZ animals, an alteration in integrin-linked kinase (ILK)-glycogen synthase kinase 3 beta (GSK-3-ß) signaling was identified (p < 0.05). Similarly, there was decreased expression (p < 0.05) of brain derived neurotropic factor (BDNF) and stargazin, an AMPAR auxiliary subunit; both are required for driving AMPA receptors to the surface of the postsynaptic membrane. Our data illustrate that altered ILK-GSK-3ß signaling due to impaired insulin signaling may decrease the trafficking and function of postsynaptic glutamate receptors; thereby, leading to synaptic deficits contributing to memory loss.

Loss of Thr286 phosphorylation disrupts synaptic CaMKIIα targeting, NMDAR activity and behavior in pre-adolescent mice.

In order to provide insight into in vivo roles of CaMKIIα autophosphorylation at Thr286 during postnatal development, behavioral, biochemical, and electrophysiological phenotypes of pre-adolescent Thr286 to Ala CaMKIIα knock-in (T286A-KI) and WT mice were examined. T286A-KI mice displayed cognitive deficits in a novel object recognition test and an anxiolytic phenotype in the elevated plus maze, suggesting disruption of normal developmental processes. At the molecular level, the ratio of total CaMKIIα to CaMKIIß in hippocampal lysates was significantly decreased≈2-fold in T286A-KI mice, and levels of both isoforms in synaptic subcellular fractions were decreased by≈80%. Total levels of GluA1 AMPA-glutamate receptor subunits and phosphorylation of GluA1 at the CaMKII site (Ser831) in synaptic fractions were unaltered, as were the frequency and amplitude of AMPAR-mediated spontaneous excitatory postsynaptic currents at hippocampal CA3-CA1 synapses. Synaptic levels of NMDA-glutamate receptor GluN1, GluN2A and GluN2B subunits also were unaltered. However, the reduced ratio of CaMKII to NMDAR subunits in synaptic fractions was linked to increased synaptic NMDAR-mediated currents in T286A-KI mice, apparently due to increased functional contributions by GluN2B NMDARs (assessed by Ro 25-6981 sensitivity). Thus, disruption of CaMKII synaptic targeting caused by elimination of Thr286 autophosphorylation leads to synaptic and behavioral deficits during pre-adolescence.

Ampakine CX516 ameliorates functional deficits in AMPA receptors in a hippocampal slice model of protein accumulation.

AMPAkines are positive modulators of AMPA receptors, and previous work has shown that these compounds can facilitate synaptic plasticity and improve learning and memory in both animals and humans; thus, their role in the treatment of cognitive impairment is worthy of investigation. In this study, we have utilized an organotypic slice model in which chloroquine-induced lysosomal dysfunction produces many of the pathogenic attributes of Alzheimer's disease. Our previous work demonstrated that synaptic AMPA receptor function is impaired in hippocampal slice cultures exhibiting lysosomal dysfunction leading to protein accumulation. The present study investigated the effect of the AMPAkine CX516 on AMPAR-mediated synaptic transmission as well as the CX516 induced modification of single channel AMPA receptor properties in this organotypic slice-culture model. In whole cell recordings from CA1 pyramidal neurons in chloroquine-treated slices we observed a significant decrease in AMPAR-mediated mEPSC frequency and amplitude indicating synaptic dysfunction. Following application of CX516, these parameters returned to nearly normal levels. Similarly, we report chloroquine-induced impairment of AMPAR single channel properties (decreased probability of opening and mean open time), and significant recovery of these properties following CX516 administration. These results suggest that AMPA receptors may be potential pharmaceutical targets for the treatment of neurodegenerative diseases, and highlights AMPAkines, in particular, as possible therapeutic agents.

Ameliorating effects of preadolescent aniracetam treatment on prenatal ethanol-induced impairment in AMPA receptor activity.

Ethanol-induced damage in the developing hippocampus may result in cognitive deficits such as those observed in fetal alcohol spectrum disorder (FASD). Cognitive deficits in FASD are partially mediated by alterations in glutamatergic synaptic transmission. Recently, we reported that synaptic transmission mediated by alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs) is impaired following fetal ethanol exposure. This finding led us to develop a rational approach for the treatment of alcohol-related cognitive deficits using aniracetam, an allosteric AMPAR modulator. In the present study, 28 to 34-day-old rats exposed to ethanol in utero were treated with aniracetam, and subsequently exhibited persistent improvement in mEPSC amplitude, frequency, and decay time. Furthermore, these animals expressed positive changes in synaptic single channel properties, suggesting that aniracetam ameliorates prenatal ethanol-induced deficits through modifications at the single channel level. Specifically, single channel open probability, conductance, mean open and closed times, and the number and burst duration were positively affected. Our findings emphasize the utility of compounds which slow the rate of deactivation and desensitization of AMPARs such as aniracetam.

Postnatal aniracetam treatment improves prenatal ethanol induced attenuation of AMPA receptor-mediated synaptic transmission.

Aniracetam is a nootropic compound and an allosteric modulator of AMPA receptors (AMPARs) which mediate synaptic mechanisms of learning and memory. Here we analyzed impairments in AMPAR-mediated synaptic transmission caused by moderate prenatal ethanol exposure and investigated the effects of postnatal aniracetam treatment on these abnormalities. Pregnant Sprague-Dawley rats were gavaged with ethanol or isocaloric sucrose throughout pregnancy, and subsequently the offspring were treated with aniracetam on postnatal days (PND) 18 to 27. Hippocampal slices prepared from these pups on PND 28 to 34 were used for the whole-cell patch-clamp recordings of AMPAR-mediated spontaneous and miniature excitatory postsynaptic currents in CA1 pyramidal cells. Our results indicate that moderate ethanol exposure during pregnancy results in impaired hippocampal AMPAR-mediated neurotransmission, and critically timed aniracetam treatment can abrogate this deficiency. These results highlight the possibility that aniracetam treatment can restore synaptic transmission and ameliorate cognitive deficits associated with the fetal alcohol syndrome.

Amyloid beta-peptide Abeta(1-42) but not Abeta(1-40) attenuates synaptic AMPA receptor function.

The brains of Alzheimer's disease (AD) patients have large numbers of plaques that contain amyloid beta (Abeta) peptides which are believed to play a pivotal role in AD pathology. Several lines of evidence have established the inhibitory role of Abeta peptides on hippocampal memory encoding, a process that relies heavily on alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor function. In this study the modulatory effects of the two major Abeta peptides, Abeta(1-40) and Abeta(1-42), on synaptic AMPA receptor function was investigated utilizing the whole cell patch clamp technique and analyses of single channel properties of synaptic AMPA receptors. Bath application of Abeta(1-42) but not Abeta(1-40) reduced both the amplitude and frequency of AMPA receptor mediated excitatory postsynaptic currents in hippocampal CA1 pyramidal neurons by approximately 60% and approximately 45%, respectively, in hippocampal CA1 pyramidal neurons. Furthermore, experiments with single synaptic AMPA receptors reconstituted in artificial lipid bilayers showed that Abeta(1-42) reduced the channel open probability by approximately 42% and channel open time by approximately 65% and increased the close times by several fold. Abeta(1-40), however, did not show such inhibitory effects on single channel properties. Application of the reverse sequence peptide Abeta(42-1) also did not alter the mEPSC or single channel properties. These results suggest that Abeta(1-42) but not Abeta(1-40) closely interacts with and exhibits inhibitory effects on synaptic AMPA receptors and may contribute to the memory impairment observed in AD.