For both considered models of Figure 1, the response rises with increasing

overall stimulus intensity in a sigmoid fashion (Figure 1C), as determined by the intrinsic nonlinearitities of each output neuron. Despite these similarities in the general shape of the stimulus-response relations, the characteristic differences of stimulus integration in the two models become strikingly apparent when one considers the contour lines of the stimulus-response plot, that is, the lines along which the response of the output neuron stays the same (Figures 1A and 1B, shown below the stimulus-response surface plots). The shape of these iso-response curves is a clear signature of the underlying signal integration or, in other words, of the arithmetic Selleckchem Ixazomib rule with which the output neuron combines its inputs.

In the simplest case, linear summation of inputs is reflected HA-1077 by straight lines in the iso-response curves (Figure 1A). The circular part of the iso-response curves in Figure 1B, on the other hand, shows the summation of squared positive inputs, whereas the line segments that run parallel to the axes indicate the thresholding of negative inputs. Iso-response curves thus reveal the nature of stimulus integration independently of the neuron’s intrinsic output nonlinearity; the output nonlinearity simply affects the response equally for all stimuli along an iso-response curve and thus does not influence the curve’s shape. To assess the nature of signal integration within the receptive field center of retinal ganglion cells, we developed an approach to measure these iso-response curves. We used a stimulus layout that subdivided the receptive field center of a ganglion cell into two halves and stimulated the cell with different levels of light intensity in these two regions (Figure 1D). Iso-response curves then consisted Thiamine-diphosphate kinase of those pairs of

visual contrast in the two receptive field halves (measured relative to the mean background light intensity) that yielded a fixed, predefined spike response of the ganglion cell. Seeking iso-response stimuli poses an obvious experimental challenge; instead of measuring responses for predefined stimuli, we need to find stimuli for predefined neuronal responses. To achieve this, we devised a closed-loop experimental design to automatically and quickly tune stimulus intensities toward the desired response, similar to previous applications in the auditory system (Gollisch et al., 2002 and Gollisch and Herz, 2005). We recorded spiking activity extracellularly from individual ganglion cells in isolated salamander retinas. For every analyzed cell, we first used the online analysis to map out the location and size of the cell’s receptive field center.

In contrast to the effect of proximity, none of the other seven precue variables showed a consistent relationship with latency (not shown). Because proximity and movement onset latency are correlated, and both of these variables are correlated with the magnitude of cue-evoked excitation (Figure 7D), we investigated the hypothesis that the proximity-related increase in firing has a causal

influence on the proximity-related decrease in latency. To test this hypothesis against competing possibilities, we used path analysis, a form of linear modeling in which the Fluorouracil correlations observed in the data are explained by assuming that a specific set of causal influences exists among the variables This analysis alone does not establish causality but identifies which causal hypotheses (models) are the best fit for the data (see Supplemental Experimental Procedures). We fit three different models for each neuron

(illustrated in Figure 7E) and compared their goodness of fit. All models assumed that proximity, measured at the moment of cue onset, influenced the subsequent firing and locomotor latency. Model 1 assumed that proximity influenced NU7441 research buy firing and that firing then influenced locomotor latency. Model 2 assumed that proximity independently influenced both firing and latency. Model 3 assumed that proximity directly influenced latency, which then influenced firing—a counterintuitive assumption given that firing typically precedes movement onset, but still theoretically possible if, for example, cue-evoked firing did

not influence latency but was itself influenced by activity in some other, unobserved structure that directly sets the latency. This analysis used only correct DS trials in which the rat was not already moving at cue onset (movement latency > 100 ms). The best-fitting model for each of the 58 cue-excited neurons was considered to be the one with the smallest Akaike’s information criterion, a measure of goodness of fit. Figure 7E shows the percentage of neurons for which each model was the best fit; these proportions are significantly different from a uniform distribution (p = 0.02, χ2 test). When comparing only two models at a time, significantly fewer neurons were best fit by model 3 when compared to model Calpain 2 (29% versus 71%; p = 0.002) or when compared to model 1 (31% versus 69%; p = 0.004). When model 1 was compared to model 2, there was no significant difference in the number of best-fitting neurons (60% versus 40% for models 1 and 2, respectively; p = 0.12). We obtained similar results when considering all correct DS trials and when considering only firing measured between 50 and 200 ms after cue onset (not shown). Using a similar approach, we also determined that the effect of lever proximity on firing is not likely to be mediated through other variables that are correlated with proximity, such as head orientation (Figure S7; Supplemental Information).

As a result, approximately 42% RGCs are lost at 8 weeks check details after microbead injection in WT mice (Figures 4B and 4C). In these animals, at 7 days after microbead

injection, there was a marked increase in CHOP expression in RGCs assessed by immunostaining (Figure S4A). However, we failed to detect the spliced form of XBP-1 at all the time points studied (3, 5, and 7 days after microbead injection) (data not shown), suggesting that similar to optic nerve injury, IOP elevation triggers differential activation of different UPR pathways in RGCs. Importantly, both CHOP KO and XBP-1s overexpression significantly reduced RGC death. The combination Z-VAD-FMK purchase of CHOP KO and XBP-1s overexpression showed a trend of further protection, but the extent of the protection did not reach the level of statistical significance as compared to CHOP KO or XBP-1s overexpression alone ( Figures 4B and 4C). These protective effects are not due to the alteration of the IOP levels, because microbead injection induced similar degrees of IOP elevation in all experimental groups ( Figure S4B). Because brain-derived neurotrophic factor (BDNF) has been shown to be protective for RGCs ( Cohen-Cory and Fraser, 1994 and Mansour-Robaey et al., 1994), we simultaneously applied BDNF and XBP-1s to the eyes of animals that received

an optic nerve crush injury ( Figure S4C) or were subjected to IOP elevation ( Figure S4D). Although BDNF alone protected RGCs to some extent, it did not lead to a significant further enhancement of RGC survival in any of these models when it was combined with XBP-1s overexpression. The mechanistic interactions between UPR and neurotrophin pathways remain to be further elucidated. To mimic a clinically relevant scenario, we also examined whether a

delayed expression of XBP-1s can be protective for RGCs in the IOP-elevated model. We thus increased IOP by microbead injection followed by introduction of AAV-XBP-1s 1 or 7 days later. Because AAV-mediated gene expression in RGCs is normally peaked at 2 weeks after infection Mephenoxalone (Martin et al., 2002 and Park et al., 2008), XBP-1s expression in RGCs is likely to occur 2–3 weeks after IOP elevation. Interestingly, such delayed AAV-XBP-1s expression still showed significant protective effects on RGCs (Figures 4D and 4E), suggesting that forced XBP-1s expression might be a promising therapeutic approach for RGC degeneration in glaucoma. A predominant hypothesis holds that ER stress activates all UPR pathways, thereby simultaneously producing antagonistic outputs that can be both protective and harmful to cells; only unresolved ER stress results in cell death (Ron and Walter, 2007).

This is accomplished by nitrosylation (and therefore inactivation) of the GPCR kinases that target the receptors for internalization (Kokkola et al., 2005 and Whalen

et al., 2007). Although the production of eCBs and NO is similarly triggered by a rise in intracellular Ca2+ in the postsynaptic cell, these retrograde signals have opposing actions on GABA release (reviewed in Feil and Kleppisch, 2008 and Wilson and Nicoll, 2002). In this study, we demonstrate that a loss in CB1R signaling is a necessary prerequisite for Enzalutamide mouse NO-mediated LTPGABA following acute food deprivation. This finding, that abolition of CB1R signaling is associated with a drive to eat, appears to be at odds with the overwhelming support for an orexigenic role of the eCB system. For example, following acute food deprivation, most evidence points to an increase in hypothalamic eCB levels (Di Marzo et al., 2001 and Kirkham STAT inhibitor et al., 2002), and CB1−/− mice exhibit hypophagia compared with their wild-type littermates (Bellocchio et al.,

2010). Recent work, however, provides clear evidence that activation of CB1Rs on GABA terminals is associated with a reduction in feeding. In the ventral striatum, CB1R-mediated inhibition of GABAergic transmission is associated with a hypophagic action of eCBs (Bellocchio et al., 2010). Thus, it is possible that a loss of CB1Rs at GABAergic terminals in the DMH in response to food deprivation is akin to removing the brake from the brain’s feeding circuitry. Our findings provide a demonstration of state-dependent plasticity in the DMH, a hypothalamic nucleus that plays a vital role in integrating information

related to caloric status and stress. Evidence suggests that DMH neurons send glutamatergic projections to the PVN (Thompson et al., 1996), an autonomic nucleus that plays a critical role in regulating food intake (Cowley et al., 1999). In agreement with this, our unpublished observations indicate that the majority of DMH neurons from which we record demonstrate antidromic activation from the PVN. An increase in GABAergic drive in the DMH would therefore others suppress glutamatergic signaling to PVN neurons that suppress food intake. This signaling would ultimately result in an enhanced drive to eat in the face of minimal food availability. Although stress-induced increases in CORT down-regulate CB1Rs and therefore promote the increase in GABA drive, signaling at the genomic glucocorticoid receptor has no effect on food intake or body weight (unpublished observations). Overall, these data demonstrate a potentially new form of state-dependent plasticity in a feeding circuit that may ensure satiety-sensing neurons in DMH neurons are not recruited when food is not available. All experiments were performed according to protocols approved by the University of Calgary Animal Care and Use Committee in accordance with guidelines established by the Canadian Council on Animal Care.

, 2008, Cuthbert et al., 2007, Ehrlich et al., 2007, Howard et al., 2010 and Migaud et al., 1998). However, other hypotheses are equally plausible. Notably, recent findings suggest that the mechanisms controlling the delivery

and maintenance of synaptic AMPARs in basal conditions and during LTP may be distinct (Adesnik et al., 2005, Ahmad et al., 2012, Jurado et al., 2013 and Sumioka et al., 2011). Synaptic cell adhesion proteins are involved in the formation, maturation, and specification of synapses (Dalva et al., 2007, Missler et al., 2012 and Siddiqui and Craig, 2011). Neuroligins (NLs) have attracted particular attention because of their synaptogenic actions when overexpressed and their genetic association with neuropsychiatric disorders (Craig IWR-1 cell line and Kang, 2007, Krueger et al., 2012 and Südhof, 2008). Although knockdown (KD) or knockout (KO) of NL1 can impair LTP, this effect may be due to the associated reduction of NMDA receptor (NMDAR)-mediated currents and spine calcium influx (Blundell et al., 2010, Chubykin et al., 2007, Kim et al., 2008 and Kwon selleck screening library et al., 2012). Recently, KD of NL1 has been reported to impair LTP in dentate gyrus granule cells and neonatal CA1 pyramidal cells independent

of an effect on NMDARs, but not at synapses on mature CA1 pyramidal cells, possibly because the LTP deficit due to NL1 KD occurs only at recently formed, immature synapses (Shipman and Nicoll, 2012). Like NLs, LRRTMs are synaptogenic in vitro, potently bind to presynaptic Nrxs, and are associated with neuropsychiatric disorders (de Wit et al., 2009, de Wit et al., 2011, Francks et al., 2007, Ko et al., 2009, Linhoff et al., 2009, Siddiqui et al., 2010 and Sousa et al., 2010). However, the functional role of LRRTMs at synapses is just beginning to be explored. LRRTMs comprise a family of four (LRRTM1–LRRTM4) homologous, Ketanserin type I transmembrane proteins with differential distribution within the brain (Laurén et al., 2003). While

the KD of LRRTM1 and/or LRRTM2 in vitro does not cause a change in synapse numbers (Ko et al., 2011), and LRRTM KDs in vitro and in vivo have yielded somewhat inconsistent results, decreases in AMPAR surface expression in vitro and AMPAR-mediated synaptic transmission in vivo have been observed (de Wit et al., 2009 and Soler-Llavina et al., 2011). Furthermore, LRRTMs may directly bind to AMPAR subunits both in vitro and in vivo (de Wit et al., 2009 and Schwenk et al., 2012). Here we used in vivo, viral-mediated KD of LRRTM1 and LRRTM2 (double knockdown, DKD) to examine the role of LRRTMs in LTP at excitatory synapses on CA1 pyramidal neurons in mouse hippocampus. LRRTM DKD blocked or dramatically impaired LTP in neonatal (postnatal days 14–18 [P14–P18]) and mature (P35–P39) CA1 pyramidal neurons, respectively.

In the contextual fear conditioning, mice learn the association between an aversive stimulus, a mild foot shock, and the context in which it was delivered. In mice that have formed an associative memory, a second exposure to the same context induces a fearful response expressed as freezing or immobility, parameters used to quantify the formation of memory (Maren, 2001). We found that mice stereotaxically injected with rAAV-shVEGFD showed significantly lower levels of freezing during the 24 hr test session than did mice injected with rAAV-shSCR ( Figure 8H). The reduction in freezing levels was not due to decreased locomotor activity or pain sensitivity because the basal

exploratory activity and reaction to shock during the training session were not different between the

two groups ( Figures selleck compound 8I and 8J). These findings together with the results obtained with the Morris water maze indicate that VEGFD is important for memory formation. In this study, we identify VEGFD as a regulator of neuronal dendrite geometry. VEGFD mediates the effects of synaptic activity and nuclear calcium-CaMKIV signaling on the maintenance of complex dendrite arborization, which is necessary for memory formation. this website Neurons, even once fully developed, remain plastic and undergo activity-dependent functional or structural alterations. Changes in gene expression – induced by synaptic activity and calcium transients propagating toward and into the nucleus (Chawla et al., 1998, Hardingham et al., 1997, Hardingham et al., 2001 and Zhang et al., 2009) – are often essential for the long-term maintenance of adaptive responses (Hardingham and Bading, 2010 and Greer and Greenberg, 2008). Dendritic trees, the branched projections of the input-receiving ends of neurons, are prime targets for activity-regulated structural alterations. The geometry of dendrites specifies the connectivity of neurons and strongly influences how signals are integrated and transmitted to the cell soma and therefore also which output

is produced. Changes in the lengths and branching patterns of dendrites would be expected to alter not only the performance of a neuron but also the computational power of the network Thalidomide the neuron is part of, ultimately causing changes in the organism’s behavior. Support for such a link between dendritic architecture and cognitive abilities comes from theoretical considerations and mathematical modeling (Häusser et al., 2000 and Segev and London, 2000) as well as from brain morphology studies of neurological diseases. In particular, shortening and simplification of dendrites have been observed in a variety of disorders that are associated with mental retardation or cognitive deficits, including genetic abnormalities, such as Down syndrome or Rett syndrome (Kaufmann and Moser, 2000), neurodegenerative conditions, including Alzheimer’s disease and aging (Dickstein et al.

Further, using this expanded set for validation experiments identified false negatives from the original screen. These results reaffirm the utility of filtering data by pathway membership to identify true positives and also using pathway membership as a search space for false negatives. In a pioneering study, Jones et al. demonstrated the significance of using pathway context in a patient setting [26]. They performed a global analysis of mutations in pancreatic cancers, but Depsipeptide research buy found little overlap in the specific mutations across patients. However, they instead found a core set of signaling pathways that consistently enriched

for patient-specific mutations. They postulate that targeting the physiological consequences of these pathways

instead of the individual mutations would Ixazomib improve therapeutic development [26]. If we consider the discrepancy between RNAi reagent performance across replicates as similar to the mutational differences between patients, these findings present more motivation for using a pathway-centered approach for functional genomic studies. Given the importance of understanding the functional context of a genetic alteration, network methods are a useful computational tool. Additionally, these tools enable the incorporation of multiple data sets and experiments to create more holistic interpretations of biological systems. Because of the availability of many experimental datasets through various

databases, data integration will be influential in future investigations [27]. Here, we review a few integrated Oxalosuccinic acid network approaches and highlight how networks have improved the interpretation of biological investigations and affected further hypothesis generation. In metastatic breast cancer, integrating copy-number variation (CNV) and gene expression data across multiple samples accurately predicted novel drivers of disease [28]. The authors used a refined method for first identifying recurrent CNVs from gene expression data and then used a Bayesian methodology to create a network of mutated genes. From this network, they found master regulators by selecting genes that had a high authority score. Mathematically, the authority score identified genes with a statistically significant number of outgoing connections as compared to the mean number of connections. To test their hypotheses about mediators for breast cancer, they performed an siRNA screen testing the effect of gene interference on cell viability. Of the gene targets that had the greatest effect on cell viability, they found a significant enrichment of their high-authority regulators [28]. This finding demonstrates that networks can synchronize disparate datasets and that network properties are viable characterizations for finding novel regulators. Utilizing a data-integration approach, Huang et al.

3% ± 5.4% of amplitude ExpT). A small, significant difference was observed in their latency: ExpT evoked mouth movements at 66 ± 4 ms, whereas UT at 96 ± 6 ms. Palatability-related

behaviors (i.e., tongue protrusions and gapes) also showed differences in the two conditions. In general Y-27632 clinical trial ExpT evoked more tongue protrusions and less gapes than UT, indicating an expectation-dependent increase of perceived palatability and reduction of aversiveness (Table S1). These types of behaviors occurred at a latency longer than 125 ms (Figures 2A, 2B, and S1; Table S1). The results presented here demonstrate the effects of cue-triggered expectation on temporal processing of gustatory stimuli in alert animals and describe cortical and amygdalar anticipatory signals responsible for this modulation. Analysis of temporal dynamics of spiking

responses in GC revealed that expectation effects were maximal in the early portion of the response. Early changes in firing rates evoked by ExpT resulted in more rapid coding of gustatory information. This effect was mediated by an increase in the number of neurons that were selective for expected tastants, by a sharpening of their tuning, and by a reduction of trial-to-trial variability selleck screening library in ensemble responses. These changes were related to anticipatory modifications of the cortical state triggered by the associative cue prior to gustatory stimulation. Cues predicting the availability of gustatory stimuli dramatically altered the activity of GC neurons. Multiple lines of evidence confirmed that cue responses in GC were not secondary to mouth movements. Instead, they appeared to emerge with learning and were the result of top-down inputs from BLA, a hub of anticipatory signals known to project to GC. Further analysis of responses

from putative pyramidal neurons unveiled a strong correlation between cue-evoked Phosphatidylinositol diacylglycerol-lyase responses and activity triggered by UT. Similarly to early activity evoked by UT, which is not specific to the chemical identity of the stimulus, cue-evoked responses acted by priming cortical circuits. The presence of the anticipatory priming before delivery of ExpT allowed GC to “save” time and more readily encode expected tastants. Although no analysis of the correlation patterns was performed on interneurons (due to the small sample size), the same analyses applied to the entire population of cue-responsive neurons yielded similar results. Gustatory cortical neurons process taste-related information via dynamic modulations of firing activity (Gutierrez et al., 2010, Jones et al., 2006, Katz et al., 2002 and Stapleton et al., 2006). Three temporal windows, each coding different aspects of gustatory experience, have been classically described in the time course of responses to UT delivered via IOC (Fontanini and Katz, 2006, Grossman et al., 2008 and Katz et al., 2002).

These experiments were performed in Tabac mice backcrossed to the inbred mouse line C57BL/6 (Figure 7C), which has been shown to have a high basal level of self-selection of nicotine (Glatt et al., 2009, Meliska et al., 1995 and Robinson et al., 1996), and in Tabac mice outbred between FBV/N mixed and Swiss Webster (Figure 7D). As shown in Figure 7C, in C57BL/6 Tabac mice, injection of buy Vandetanib the LV-α5N virus reversed their nicotine aversion in comparison to mice injected with the control virus. In outbred Tabac mice injected with the control virus,

we observed no alteration in nicotine aversion (Figure 7D) with respect to uninjected Tabac mice (Figure 6C). Importantly, infection with LV-α5N virus reversed nicotine aversion in Tabac mice (Figure 7D), restoring nicotine consumption in α5 D397N-infected Tabac mice to levels evident in WT mice (Figure 6C). These results demonstrate a major role for the MHb in nicotine consumption. Human genetic studies have established an association between the CHRNB4-CHRNA3-CHRNA5

locus and tobacco use ( Amos et al., 2010b, Saccone et al., 2009, Thorgeirsson et al., 2008 and Weiss et al., 2008). Here we report a mouse model (Tabac mice) with altered nicotine consumption and CPA caused by elevated levels of β4, enhanced nicotine-evoked currents, and increased surface expression of functional nAChRs at endogenous sites. The ability of β4 to enhance nicotine-evoked currents depends on a single critical residue (S435) located in the intracellular vestibule of the receptor. Interestingly, modeling studies revealed that one this website of the most common SNPs associated with tobacco usage, D398N in the α5 subunit, also maps to this domain. Functional analyses of this variant demonstrate that alterations in this domain can result in profound effects on nicotine-evoked currents. many Based on our studies in Tabac mice in which enhanced current is associated with increased aversion to nicotine, we predicted that the α5 variant (corresponding to D397N in

mice) should increase nicotine consumption consistent with its association with smoking. To test this idea, and given that the MHb contains a very high concentration of endogenous α3β4α5 receptors and elevated levels of β4 driven by the Tabac transgene, we introduced the α5 variant by viral-mediated transduction in habenular neurons of Tabac mice. The reversal of the nicotine aversion achieved in Tabac mice observed in these experiments demonstrates that the MHb plays a major regulatory role in nicotine consumption. Three main points are addressed in this study. First, changes both in the coordinated expression of α3β4α5 subunits (i.e., overexpression of the β4 subunit) and in single residues (i.e., in vivo viral-mediated expression of the α5 D397N variant) have a strong influence on nicotine consumption in mice.

The enhancement occurs without any change in surface GluK2 protein. However, expression of GluK2 does enhance the surface expression PLX3397 mw of NETO2. In cerebella from mice lacking GluK2, the levels of NETO2 are reduced by 60%, and much of this decrease is attributable to the loss of surface NETO2. Similar to the action of TARPs on AMPARs, NETO2 slows deactivation and desensitization and speeds the recovery from desensitization of

GluK2. To examine the possible effects of NETO2 on synaptically evoked KAR-mediated currents, a mutant of GluK2 with reduced desensitization was expressed in stargazer CGNs. When NETO2 is coexpressed with this mutant, the frequency of mEPSCs increases and their time course is slowed. Finally, to determine if NETO2 is normally associated with KARs, the authors used shRNA to knock down endogenous NETO2 in hippocampal neurons. They found that the KA/Glu ratio of currents evoked by KARs is reduced with the knockdown of NETO2. These results raise a number

of interesting questions. buy BMN 673 There are a number of subunits that are involved in KAR function in the brain. Does NETO2 have similar effects on the other types of KARs? Does the related protein NETO1 also serve as a KAR auxiliary subunit? Although the authors show that NETO2 can slow the kinetics of synaptic currents generated by a mutated GluK2, it will be of interest to know of what happens to well-characterized KAR-mediated EPSCs when NETO2 is deleted. Furthermore, it is remarkable that NETO1 and NETO2, which are homologous to each other, act on entirely separate classes of iGluR. Can NETO2 also act on NMDARs? Is it possible that NETO proteins are auxiliary subunits for both KARs and NMDARs? Clearly there is much to be resolved in this rapidly evolving area. Early studies on fast excitatory synaptic transmission in

the brain emphasized the stereotyped nature of excitatory synapses whereby information is transmitted faithfully from one neuron to another. However, the discovery of synaptic plasticity and the cloning of the various AMPAR subunit genes put this simplistic view to rest. Importantly, receptors assembled from different subunits have strikingly different biophysical properties. Add to this the discovery that subunits exist as splice variants and can undergo RNA editing, both of which control receptor gating, and one begins to reach a daunting level of complexity. Given this background one can reasonably wonder why AMPARs and other iGluRs should need various auxiliary subunits and the mind-boggling combinatorial possibilities that come with these newly discovered proteins. Only further studies will shed light on this general question. There are, however, a number of specific and perhaps more tractable questions that arise from this research.