Efficacy and safety of totally laparoscopic gastrectomy with uncut Roux-en-Y for gastric cancer: a dual-center retrospective study.

BACKGROUND: Uncut Roux-en-Y (URY) effectively alleviates the prevalent complexities connected with RY, such as Roux-en-Y stasis syndrome (RSS). Nevertheless, for gastric cancer (GC) patients, it is still controversial whether URY has an impact on long-term prognosis and whether it has fewer afferent loop recanalization. Therefore, compare whether URY and RY have differences in prognosis and long-term complications of GC patients undergoing totally laparoscopic gastrectomy (TLG). METHODS: We analyzed the data of patients who underwent TLG combined with digestive tract reconstruction from dual-center between 2016 and 2022. Only patients undergoing URY and RY were selected for analysis. Relapse-free survival (RFS) and overall survival (OS) were estimated. Bias between the groups was reduced by propensity score matching (PSM). The Cox proportional hazard regression model was used to further analyze the influence of URY on prognosis. RESULTS: Two hundred forty two GC patients were enrolled. The URY had significantly shorter operation time, liquid food intake time, and in-hospital stays than the RY (P < 0.001). The URY had fewer long-term and short-term postoperative complications than the RY, especially with regard to RSS, reflux esophagitis, and reflux gastritis. The 3-year and 5-year OS of the URY group and the RY group before PSM: 87.5% vs. 65.6% (P < 0.001) and 81.4% vs. 61.7% (P = 0.001). PSM and Cox multivariate analysis confirmed that compared to RY, URY can improve the short-term and long-term prognosis of GC patients. CONCLUSION: TLG combined with URY for GC, especially for advanced, older, and poorly differentiated patients, may promote postoperative recovery and improve long-term prognosis.

Traumatic brain injury-induced inflammatory changes in the olfactory bulb disrupt neuronal networks leading to olfactory dysfunction.

Approximately 20-68% of traumatic brain injury (TBI) patients exhibit trauma-associated olfactory deficits (OD) which can compromise not only the quality of life but also cognitive and neuropsychiatric functions. However, few studies to date have examined the impact of experimental TBI on OD. The present study examined inflammation and neuronal dysfunction in the olfactory bulb (OB) and the underlying mechanisms associated with OD in male mice using a controlled cortical impact (CCI) model. TBI caused a rapid inflammatory response in the OB as early as 24 h post-injury, including elevated mRNA levels of proinflammatory cytokines, increased numbers of microglia and infiltrating myeloid cells, and increased IL1ß and IL6 production in these cells. These changes were sustained for up to 90 days after TBI. Moreover, we observed significant upregulation of the voltage-gated proton channel Hv1 and NOX2 expression levels, which were predominantly localized in microglia/macrophages and accompanied by increased reactive oxygen species production. In vivo OB neuronal firing activities showed early neuronal hyperexcitation and later hypo-neuronal activity in both glomerular layer and mitral cell layer after TBI, which were improved in the absence of Hv1. In a battery of olfactory behavioral tests, WT/TBI mice displayed significant OD. In contrast, neither Hv1 KO/TBI nor NOX2 KO/TBI mice showed robust OD. Finally, seven days of intranasal delivery of a NOX2 inhibitor (NOX2ds-tat) ameliorated post-traumatic OD. Collectively, these findings highlight the importance of OB neuronal networks and its role in TBI-mediated OD. Thus, targeting Hv1/NOX2 may be a potential intervention for improving post-traumatic anosmia.

Visual analysis of global research on immunotherapy for gastric cancer: A literature mining from 2012 to 2022.

Gastric cancer (GC) is one of the most common malignancies. Immunotherapy becomes an indispensable part of GC. This study conducts bibliometric analysis of immunotherapy for GC to clarify the research status and identify potential new research directions. VOS viewer and CiteSpace visualization software were used to demonstrate collaborations and correlations. A total of 1141 English publications from 2012 to 2022 were included. The number of publications increased year by year. The publications were mainly from China (n = 579, 50.70%), followed by the United States. Fudan University published the most publications (n = 48, 4.21%). Frontiers in Oncology and Journal of Clinical Oncology ranked first in cited and co-cited journals, respectively. Kim Kyoung-Mee published the most publications on immunotherapy for GC (n = 14). The clustering of timeline view and co-cited references show the hotspot transformation on immunotherapy for GC. Initially, the hot topic was "cytokine-induced killer cells" and "myeloid-derived suppressor cells." In recent years, the focus has turned to "targeted therapy." "CAR-T" has become the hottest topic, and GC has entered precision therapy phase. Screening patients who can benefit from immunotherapy is key to improving prognosis. The combination of immunotherapy with other treatment options, such as chemotherapy and targeted therapy, is currently the focus of research. Chimeric antigen receptor T cell will be further studied in the future.

Bibliometrics is one of the main tools in the current research and hot spots. Immunotherapy becomes an indispensable part of gastric cancer. Chimeric antigen receptor T cells will play an important role for gastric cancer.

Brain injury accelerates the onset of a reversible age-related microglial phenotype associated with inflammatory neurodegeneration.

Lipofuscin is an autofluorescent (AF) pigment formed by lipids and misfolded proteins, which accumulates in postmitotic cells with advanced age. Here, we immunophenotyped microglia in the brain of old C57BL/6 mice (>18 months old) and demonstrate that in comparison to young mice, one-third of old microglia are AF, characterized by profound changes in lipid and iron content, phagocytic activity, and oxidative stress. Pharmacological depletion of microglia in old mice eliminated the AF microglia following repopulation and reversed microglial dysfunction. Age-related neurological deficits and neurodegeneration after traumatic brain injury (TBI) were attenuated in old mice lacking AF microglia. Furthermore, increased phagocytic activity, lysosomal burden, and lipid accumulation in microglia persisted for up to 1 year after TBI, were modified by APOE4 genotype, and chronically driven by phagocyte-mediated oxidative stress. Thus, AF may reflect a pathological state in aging microglia associated with increased phagocytosis of neurons and myelin and inflammatory neurodegeneration that can be further accelerated by TBI.

Totally laparoscopic total gastrectomy with Uncut Roux-en-Y for gastric cancer may improve prognosis: A propensity score matching comparative study.

Background: Laparoscopic total gastrectomy (LTG) with Roux-en-Y (RY) is often accompanied by a series of complications. Uncut RY (URY) can effectively reduce Roux stasis syndrome (RSS) in laparoscopic distal gastrectomy. To determine whether totally LTG (TLTG) with URY for gastric cancer (GC) can replace RY in short-term and long-term prognosis. Methods: This comparative retrospective study selected GC patients from 2016 to 2022. The patients were divided into URY group and RY group. Cox multivariate proportional hazard regression analysis was used to explore the independent prognostic factors. Propensity score matching (PSM) was used to reduce bias. Results: A total of 100 GC patients met the inclusion criteria. Compared to RY group, URY group showed significant advantages in operation time and length of hospital stay. In addition, URY group can significantly reduce short-term and long-term complications, especially RSS. The 1-, 3- and 5-year progression free survival (PFS) of URY group and RY group were 90.4% vs. 67.8% (P=0.005), 76.6% vs. 52.6% (P=0.009) and 76.6% vs. 32.8% (P<0.001), respectively. After PSM, the advantage of URY in PFS was verified again, while there was no significant difference in overall survival (OS) between the two groups. Cox multivariate analysis suggested that lower RSS was associated with better PFS. Conclusions: TLTG with URY for GC helps control disease progression, speed up recovery and reduce short and long-term complications, especially RSS.

Light Hydrocarbon (C5-C7) Geochemistry in the Northern Margin of the Qaidam Basin, Northeastern Tibetan Plateau: Gas Mixing and Hydrocarbon Charge History.

Twenty natural gases from the northern margin of the Qaidam Basin were collected and examined for the composition and stable carbon isotopic characteristics of gas and light hydrocarbons (C5-C7). The results reveal that the carbon isotopes of iso-alkanes and cyclo-alkanes in light hydrocarbons are mainly controlled by the bioprecursors, whereas the carbon isotopes of n-alkanes and aromatics in light hydrocarbons are primarily influenced by the bioprecursors and maturity. Based on the genetic types obtained from C1-C3 and C5-C7 fractions, three types of gases are identified: coal-type gas, oil-type gas, and mixed gas. Coal-type gas dominates the northern margin of the Qaidam Basin, oil-type gas is mostly distributed in the Lenghu no. 3 field, and mixed gas is mainly developed in the Dongping and Mabei fields. According to the maturity obtained from δ13C1 and heptane and isoheptane ratios, the petroleum charge period is studied in combination with burial history and hydrocarbon generation history, and the result is roughly well matched with the research of homogeneous temperatures of petroleum inclusions. Furthermore, the generation temperature of the major reservoired hydrocarbons calculated from C7 light hydrocarbon compositions ranges from 125.0 to 135.9 °C, suggesting that a major petroleum charge event may occur primarily during the Shangganchaigou period (N1) in most fields. The deep paleo uplifts adjacent to the hydrocarbon-generating depressions at the margin of the basin and uplift zone in the inner basin are estimated as favorable areas for further exploration in the northern margin of the Qaidam Basin.

Adjoint traveltime tomography unravels a scenario of horizontal mantle flow beneath the North China craton.

The North China craton (NCC) was dominated by tectonic extension from late Cretaceous to Cenozoic, yet seismic studies on the relationship between crust extension and lithospheric mantle deformation are scarce. Here we present a three dimensional radially anisotropic model of NCC derived from adjoint traveltime tomography to address this issue. We find a prominent low S-wave velocity anomaly at lithospheric mantle depths beneath the Taihang Mountains, which extends eastward with a gradually decreasing amplitude. The horizontally elongated low-velocity anomaly is also featured by a distinctive positive radial anisotropy (VSH > VSV). Combining geodetic and other seismic measurements, we speculate the presence of a horizontal mantle flow beneath central and eastern NCC, which led to the extension of the overlying crust. We suggest that the rollback of Western Pacific slab likely played a pivotal role in generating the horizontal mantle flow at lithospheric depth beneath the central and eastern NCC.

CCKergic Tufted Cells Differentially Drive Two Anatomically Segregated Inhibitory Circuits in the Mouse Olfactory Bulb.

Delineation of functional synaptic connections is fundamental to understanding sensory processing. Olfactory signals are synaptically processed initially in the olfactory bulb (OB) where neural circuits are formed among inhibitory interneurons and the output neurons mitral cells (MCs) and tufted cells (TCs). TCs function in parallel with but differently from MCs and are further classified into multiple subpopulations based on their anatomic and functional heterogeneities. Here, we combined optogenetics with electrophysiology to characterize the synaptic transmission from a subpopulation of TCs, which exclusively express the neuropeptide cholecystokinin (CCK), to two groups of spatially segregated GABAergic interneurons, granule cells (GCs) and glomerular interneurons in mice of both sexes with four major findings. First, CCKergic TCs receive direct input from the olfactory sensory neurons (OSNs). This monosynaptic transmission exhibits high fidelity in response to repetitive OSN input. Second, CCKergic TCs drive GCs through two functionally distinct types of monosynaptic connections: (1) dendrodendritic synapses onto GC distal dendrites via their lateral dendrites in the superficial external plexiform layer (EPL); (2) axodendritic synapses onto GC proximal dendrites via their axon collaterals or terminals in the internal plexiform layer (IPL) on both sides of each bulb. Third, CCKergic TCs monosynaptically excite two subpopulations of inhibitory glomerular interneurons via dendrodendritic synapses. Finally, sniff-like patterned activation of CCKergic TCs induces robust frequency-dependent depression of the dendrodendritic synapses but facilitation of the axodendritic synapses. These results demonstrated important roles of the CCKergic TCs in olfactory processing by orchestrating OB inhibitory activities.SIGNIFICANCE STATEMENT Neuronal morphology and organization in the olfactory bulb (OB) have been extensively studied, however, the functional operation of neuronal interactions is not fully understood. We combined optogenetic and electrophysiological approaches to investigate the functional operation of synaptic connections between a specific population of excitatory output neuron and inhibitory interneurons in the OB. We found that these output neurons formed distinct types of synapses with two populations of spatially segregated interneurons. The functional characteristics of these synapses vary significantly depending on the presynaptic compartments so that these output neurons can dynamically rebalance inhibitory feedback or feedforward to other neurons types in the OB in response to dynamic rhythmic inputs.

Dopamine Suppresses Synaptic Responses of Fan Cells in the Lateral Entorhinal Cortex to Olfactory Bulb Input in Mice.

The lateral entorhinal cortex (LEC) is involved in odor discrimination, odor-associative multimodal memory, and neurological or neuropsychiatric disorders. It receives direct axonal projections from both olfactory bulb (OB) output neurons and midbrain dopaminergic neurons. However, the cellular targets in LEC receiving direct synaptic input from OB output neuron, the functional characteristics of these synapses, and whether or how dopamine (DA) modulates the OB-LEC pathway remain undetermined. We addressed these questions in the present study by combing optogenetic and electrophysiological approaches with four major findings: (1) selective activation of OB input elicited glutamate-mediated monosynaptic responses in all fan cells, the major output neurons in layer II of the LEC; (2) this excitatory synaptic transmission exhibited robust paired-pulse facilitation (PPF), a presynaptically derived short-term synaptic plasticity; (3) DA dramatically attenuated the strength of the OB input-fan cell synaptic transmission via activation of D1 receptors; and (4) DA altered the PPF of this transmission but neither intrinsic properties of postsynaptic neurons nor the kinetic profile of postsynaptic responses, suggesting that presynaptic mechanisms underlie the DA inhibitory actions. This study for the first time demonstrates the FCs in the LEC layer II as the postsynaptic target of direct OB input and characterizes DA modulation of the OB input-fan cell pathway. These findings set the foundation for future studies to examine the synaptic transmission from the OB output neuron axon terminals to other potential cell types in the LEC and to pinpoint the pathophysiological mechanisms underlying olfactory deficits associated with DA-relevant neurological and neuropsychiatric disorders.

Dopaminergic Modulation of Glomerular Circuits in the Mouse Olfactory Bulb.

Dopaminergic neurons are located in several brain areas including the olfactory bulb (OB) and involved in many physiological and pathophysiological processes. In the OB, dopamine (DA) is released exclusively by a population of interneurons termed short axon cells (SACs) in the glomerular layer, the initial synaptic integration site of the whole olfactory system. SACs corelease GABA and extend their processes to many glomeruli forming the interglomerular circuit. Two major groups of DA receptors D1-like (D1LRs) and D2-like (D2LRs) types are differentially distributed in the OB, i.e., D1LRs are broadly present except the most superficial olfactory nerve (ON) layer while D2LRs are predominantly confined to the ON and glomerular layers, suggesting that they mediate different physiological functions. In contrast to the well-known D2LR-mediated presynaptic inhibition of ON terminals in the OB, the cellular and circuit targets of the D1LR-mediated DA actions remain unclear even though D1LR activation improves odor detection and discrimination. We recently demonstrated that endogenous DA released from SACs or exogenous DA excites a population of excitatory glomerular neurons termed external tufted cells (ETCs) via D1LRs. But the physiological significance of this D1LR activation is largely unknown. In the present study, we addressed these questions by a systematic examination of exogenous DA actions on synaptic activities and excitabilities in most glomerular neurons and OB output neurons with the following major findings: (1) DA via D1LRs enhances OB output by potentiating the ETC-mediated feedforward excitation to the OB output neurons but suppresses spontaneous excitatory synaptic activities in both types of inhibitory glomerular interneurons periglomerular (PGCs) and SACs; (2) this suppression of excitatory synaptic activities in PGCs and SACs depends on activation of GABAB receptors; (3) DA via D1LRs augments spontaneous inhibitory synaptic activities in all glomerular neurons and OB output neurons; (4) DA selectively activates SACs via D1LRs. These findings suggest that activation of D1LRs elevates the system's sensitivity to odor stimuli and provide a mechanistic basis for the functional roles of DA in modulating odor detection and discrimination.

Reciprocal Inhibitory Glomerular Circuits Contribute to Excitation-Inhibition Balance in the Mouse Olfactory Bulb.

The major inhibitory interneurons in olfactory bulb (OB) glomeruli are periglomerular cells (PGCs) and short axon cells (SACs). PGCs and SACs provide feedforward inhibition to all classes of projection neurons, but inhibition between PGCs and SACs is not well understood. We crossed Cre and GFP transgenic mice and used virally-delivered optogenetic constructs to selectively activate either SACs or GAD65cre-ChR2-positive PGCs while recording from identified GAD65cre-ChR2-positive PGCs or SACs, respectively, to investigate inhibitory interactions between these two interneuron types. We show that GAD65cre-ChR2-positive PGCs robustly inhibit SACs and SACs strongly inhibit PGCs. SACs form the interglomerular circuit, which inhibits PGCs in distant glomeruli. Activation of GAD65cre-ChR2-positive PGCs monosynaptically inhibit mitral cells (MCs), which complements recent findings that SACs directly inhibit MCs. Thus, both classes of glomerular inhibitory neurons inhibit each other, as well as OB output neurons. We further show that olfactory nerve input to one glomerulus engages the interglomerular circuit and inhibits PGCs in distant glomeruli. Sensory activation of the interglomerular circuit directly inhibits output neurons in other glomeruli and by inhibiting intraglomerular PGCs, may potentially disinhibit output neurons in other glomeruli. The nature and context of odorant stimuli may determine whether inhibition or excitation prevails so that odors are represented in part by patterns of active and inactive glomeruli.

Intracerebroventricular Administration of Neural Stem Cells after Cardiac Arrest.

Cardiac arrest (CA) is a serious disease with high rates of mortality and disability worldwide. Currently, neither pharmacological intervention nor therapeutic hypothermia can reverse the neural injury caused by CA. Neural stem cell therapy is a promising treatment for brain injury. We investigated the effects of the intracerebroventricular (ICV) administration of human neural stem cells (hNSCs) on global brain ischemia injury after CA. Twelve Long-Evans rats (4 Male and 8 female) subjected to 8-min asphyxia-CA were randomly assigned to hNSC treatment (n=7) or control group (n=5). The hNSCs were slowly infused into the left lateral ventricular 3 hours after resuscitation. An additional two rats subjected to 8-min asphyxia-CA were euthanized at 4 weeks after resuscitation to confirm the survival and function of transplanted PKH26 pre-labeled hNSCs by brain slides and whole cell patch clamp. Electrophysiological monitoring, quantitative EEG value (qEEG-IQ) and neurological deficit score (NDS) were used to evaluate the functional outcome. Immunofluorescence staining was used to investigate the survival of neurons and track migration of hNSCs. There was a significant improvement on the behavior tests evaluated as a subgroup of NDS (p <; 0.05) in the NSCs group than the control group. Immunofluorescent co-staining of PKH26 and NeuN verified the neuronal differentiation from transplanted PKH26+ hNSCs in the hippocampus CA1 and cortex 4 weeks after CA. The whole-cell patch clamp technique confirmed the spontaneous firing activity that was recorded in cell-attached mode from the functional mature neurons derived from transplanted cells. Transplanted hNSCs via ICV administration markedly improved neurologic outcomes after CA. Further studies are needed to elucidate the neuroprotective mechanism.

Cholecystokinin selectively activates short axon cells to enhance inhibition of olfactory bulb output neurons.

KEY POINTS: Cholecystokinin (CCK) via CCK-B receptors significantly enhances the GABAA receptor-mediated synaptic inhibition of principal olfactory bulb (OB) output neurons. This CCK action requires action potentials in presynaptic neurons. The enhanced inhibition of OB output neurons is a result of CCK-elevated inhibitory input from the glomerular circuit. CCK modulation of the glomerular circuit also leads to potentiated presynaptic inhibition of olfactory nerve terminals and postsynaptic inhibition of glomerular neurons. Selective excitation of short axon cells underlies the CCK-potentiated glomerular inhibition. ABSTRACT: Neuropeptides such as cholecystokinin (CCK) are important for many brain functions, including sensory processing. CCK is predominantly present in a subpopulation of excitatory neurons and activation of CCK receptors is implicated in olfactory signal processing in the olfactory bulb (OB). However, the cellular and circuit mechanisms underlying the actions of CCK in the OB remain elusive. In the present study, we characterized the effects of CCK on synaptic inhibition of the principal OB output neurons mitral/tufted cells (MTCs) followed by mechanistic analyses at both circuit and cellular levels. First, we found that CCK via CCK-B receptors enhances the GABAA receptor-mediated spontaneous IPSCs in MTCs. Second, CCK does not affect the action potential independent miniature IPSCs in MTCs. Third, CCK potentiates glomerular inhibition resulting in increased GABAB receptor-mediated presynaptic inhibition of olfactory nerve terminals and enhanced spontaneous IPSCs in MTCs and glomerular neurons. Fourth, CCK enhances miniature IPSCs in the excitatory external tufted cells, although neither in the inhibitory short axon cells (SACs) nor in periglomerular cells (PGCs). Finally, CCK excites all tested SACs and a very small minority of GABAergic neurons in the granule cell layer or in periglomerular cells, but not in deep SACs. These results demonstrate that CCK selectively activates SACs to engage the SAC-formed interglomerular circuit and thus elevates inhibition broadly in the OB glomerular layer. This modulation may prevent the system from saturating in response to a high concentration of odourants or facilitate the detection of weak stimuli by increasing signal-to-noise ratio.

The Interglomerular Circuit Potently Inhibits Olfactory Bulb Output Neurons by Both Direct and Indirect Pathways.

UNLABELLED: Sensory processing shapes our perception. In mammals, odor information is encoded by combinatorial activity patterns of olfactory bulb (OB) glomeruli. Glomeruli are richly interconnected by short axon cells (SACs), which form the interglomerular circuit (IGC). It is unclear how the IGC impacts OB output to downstream neural circuits. We combined in vitro and in vivo electrophysiology with optogenetics in mice and found the following: (1) the IGC potently and monosynaptically inhibits the OB output neurons mitral/tufted cells (MTCs) by GABA release from SACs: (2) gap junction-mediated electrical coupling is strong for the SAC→MTC synapse, but negligible for the SAC→ETC synapse; (3) brief IGC-mediated inhibition is temporally prolonged by the intrinsic properties of MTCs; and (4) sniff frequency IGC activation in vivo generates persistent MTC inhibition. These findings suggest that the temporal sequence of glomerular activation by sensory input determines which stimulus features are transmitted to downstream olfactory networks and those filtered by lateral inhibition. SIGNIFICANCE STATEMENT: Odor identity is encoded by combinatorial patterns of activated glomeruli, the initial signal transformation site of the olfactory system. Lateral circuit processing among activated glomeruli modulates olfactory signal transformation before transmission to higher brain centers. Using a combination of in vitro and in vivo optogenetics, this work demonstrates that interglomerular circuitry produces potent inhibition of olfactory bulb output neurons via direct chemical and electrical synapses as well as by indirect pathways. The direct inhibitory synaptic input engages mitral cell intrinsic membrane properties to generate inhibition that outlasts the initial synaptic action.

Subsecond Regulation of Synaptically Released Dopamine by COMT in the Olfactory Bulb.

UNLABELLED: The efficacy of neurotransmission depends on multiple factors, including presynaptic vesicular release of transmitter, postsynaptic receptor populations and clearance/inactivation of the transmitter. In the olfactory bulb (OB), short axon cells (SACs) form an interglomerular circuit that uses GABA and dopamine (DA) as cotransmitters. Selective optical activation of SACs causes GABA and DA co-release, resulting in a fast, postsynaptic GABA inhibitory response and a slower G-protein-coupled DA rebound excitation. In most systems, vesicular release of DA is cleared by the dopamine transporter (DAT). However, in the OB, high levels of specific DA metabolites suggest that enzymatic catalysis by catechol-O-methyl-transferase (COMT) predominates over DAT re-uptake. To assess this possibility we measured the amount of the DA breakdown enzyme, COMT, present in the OB. Compared with the striatum, the brain structure richest in DA terminals, the OB contains 50% more COMT per unit of tissue. Furthermore, the OB has dramatically less DAT compared with striatum, supporting the idea that COMT enzymatic breakdown, rather than DAT recycling, is the predominant mechanism for DA clearance. To functionally assess COMT inactivation of vesicular release of DA we used fast-scan cyclic voltammetry and pharmacological blockade of COMT. In mice expressing ChR2 in tyrosine hydroxylase-containing neurons, optical activation of SACs evoked robust DA release in the glomerular layer. The COMT inhibitor, tolcapone, increased the DA signal ∼2-fold, whereas the DAT inhibitor GBR12909 had no effect. Together, these data indicate that the OB preferentially employs COMT enzymatic inactivation of vesicular release of DA. SIGNIFICANCE STATEMENT: In the olfactory bulb (OB), odors are encoded by glomerular activation patterns. Dopaminergic short axon neurons (SACs) form an extensive network of lateral connections that mediate cross talk among glomeruli, releasing GABA and DA onto sensory nerve terminals and postsynaptic neurons. DA neurons are ∼10-fold more numerous in OB than in ventral tegmental areas that innervate the striatum. We show that OB has abundant expression of the DA catalytic enzyme catechol-O-methyl-transferase (COMT), but negligible expression of the dopamine transporter. Using optogenetics and fast-scan cyclic voltammetry, we show that inhibition of COMT increases DA signals ∼2-fold. Thus, in contrast to the striatum, which has the brain's highest proportion of DAergic synapses, the DA catalytic pathway involving COMT predominates over re-uptake in OB.

The anti-dementia drug candidate, (-)-clausenamide, improves memory impairment through its multi-target effect.

Multi-target drugs, such as the cocktail therapy used for treating AIDS, often show stronger efficacy than single-target drugs in treating complicated diseases. This review will focus on clausenamide (clau), a small molecule compound originally isolated from the traditional Chinese herbal medicine, Clausenalansium. The finding of four chiral centers in clau molecules predicted the presence of 16 clau enantiomers, including (-)-clau and (+)-clau. All of the predicted enantiomers have been successfully synthesized via innovative chemical approaches, and pharmacological studies have demonstrated (-)-clau as a eutomer and (+)-clau as a distomer in improving cognitive function in both normal physiological and pathological conditions. Mechanistically, the nootropic effect of (-)-clau is mediated by its multi-target actions, which include mild elevation of intracellular Ca(2+) concentrations, modulation of the cholinergic system, regulation of synaptic plasticity, and activation of cellular and molecular signaling pathways involved in learning and memory. Furthermore, (-)-clau suppresses the pathogenesis of Alzheimer's disease by inhibiting multiple etiological processes: (1) beta amyloid protein-induced intracellular Ca(2+) overload and apoptosis and (2) tau hyperphosphorylation and neurodegeneration. In conclusion, the nature of the multi-target actions of (-)-clau substantiates it as a promising chiral drug candidate for enhancing human cognition in normal conditions and treating memory impairment in neurodegenerative diseases.

Muscarinic receptors modulate dendrodendritic inhibitory synapses to sculpt glomerular output.

Cholinergic [acetylcholine (ACh)] axons from the basal forebrain innervate olfactory bulb glomeruli, the initial site of synaptic integration in the olfactory system. Both nicotinic acetylcholine receptors (nAChRs) and muscarinic acetylcholine receptors (mAChRs) are expressed in glomeruli. The activation of nAChRs directly excites both mitral/tufted cells (MTCs) and external tufted cells (ETCs), the two major excitatory neurons that transmit glomerular output. The functional roles of mAChRs in glomerular circuits are unknown. We show that the restricted glomerular application of ACh causes rapid, brief nAChR-mediated excitation of both MTCs and ETCs in the mouse olfactory bulb. This excitation is followed by mAChR-mediated inhibition, which is blocked by GABAA receptor antagonists, indicating the engagement of periglomerular cells (PGCs) and/or short axon cells (SACs), the two major glomerular inhibitory neurons. Indeed, selective activation of glomerular mAChRs, with ionotropic GluRs and nAChRs blocked, increased IPSCs in MTCs and ETCs, indicating that mAChRs recruit glomerular inhibitory circuits. Selective activation of glomerular mAChRs in the presence of tetrodotoxin increased IPSCs in all glomerular neurons, indicating action potential-independent enhancement of GABA release from PGC and/or SAC dendrodendritic synapses. mAChR-mediated enhancement of GABA release also presynaptically suppressed the first synapse of the olfactory system via GABAB receptors on sensory terminals. Together, these results indicate that cholinergic modulation of glomerular circuits is biphasic, involving an initial excitation of MTC/ETCs mediated by nAChRs followed by inhibition mediated directly by mAChRs on PGCs/SACs. This may phasically enhance the sensitivity of glomerular outputs to odorants, an action that is consistent with recent in vivo findings.

Olfactory bulb short axon cell release of GABA and dopamine produces a temporally biphasic inhibition-excitation response in external tufted cells.

Evidence for coexpression of two or more classic neurotransmitters in neurons has increased, but less is known about cotransmission. Ventral tegmental area (VTA) neurons corelease dopamine (DA), the excitatory transmitter glutamate, and the inhibitory transmitter GABA onto target cells in the striatum. Olfactory bulb (OB) short axon cells (SACs) form interglomerular connections and coexpress markers for DA and GABA. Using an optogenetic approach, we provide evidence that mouse OB SACs release both GABA and DA onto external tufted cells (ETCs) in other glomeruli. Optical activation of channelrhodopsin specifically expressed in DAergic SACs produced a GABA(A) receptor-mediated monosynaptic inhibitory response, followed by DA-D(1)-like receptor-mediated excitatory response in ETCs. The GABA(A) receptor-mediated hyperpolarization activates I(h) current in ETCs; synaptically released DA increases I(h), which enhances postinhibitory rebound spiking. Thus, the opposing actions of synaptically released GABA and DA are functionally integrated by I(h) to generate an inhibition-to-excitation "switch" in ETCs. Consistent with the established role of I(h) in ETC burst firing, we show that endogenous DA release increases ETC spontaneous bursting frequency. ETCs transmit sensory signals to mitral/tufted output neurons and drive intraglomerular inhibition to shape glomerulus output to downstream olfactory networks. GABA and DA cotransmission from SACs to ETCs may play a key role in regulating output coding across the glomerular array.

Intraglomerular inhibition shapes the strength and temporal structure of glomerular output.

Odor signals are transmitted to the olfactory bulb by olfactory nerve (ON) synapses onto mitral/tufted cells (MCs) and external tufted cells (ETCs). ETCs, in turn, provide feedforward excitatory input to MCs. MC and ETCs are also regulated by inhibition: intraglomerular and interglomerular inhibitory circuits act at MC and ETC apical dendrites; granule cells (GCs) inhibit MC lateral dendrites via the MC→GC→MC circuit. We investigated the contribution of intraglomerular inhibition to MC and ETCs responses to ON input. ON input evokes initial excitation followed by early, strongly summating inhibitory postsynaptic currents (IPSCs) in MCs; this is followed by prolonged, intermittent IPSCs. The N-methyl-d-aspartate receptor antagonist dl-amino-5-phosphovaleric acid, known to suppress GABA release by GCs, reduced late IPSCs but had no effect on early IPSCs. In contrast, selective intraglomerular block of GABA(A) receptors eliminated all early IPSCs and caused a 5-fold increase in ON-evoked MC spiking and a 10-fold increase in response duration. ETCs also receive intraglomerular inhibition; blockade of inhibition doubled ETC spike responses. By reducing ETC excitatory drive and directly inhibiting MCs, intraglomerular inhibition is a key factor shaping the strength and temporal structure of MC responses to sensory input. Sensory input generates an intraglomerular excitation-inhibition sequence that limits MC spike output to a brief temporal window. Glomerular circuits may dynamically regulate this input-output window to optimize MC encoding across sniff-sampled inputs.

Serotonin modulates the population activity profile of olfactory bulb external tufted cells.

Serotonergic neurons in the raphe nuclei constitute one of the most prominent neuromodulatory systems in the brain. Projections from the dorsal and median raphe nuclei provide dense serotonergic innervation of the glomeruli of olfactory bulb. Odor information is initially processed by glomeruli, thus serotonergic modulation of glomerular circuits impacts all subsequent odor coding in the olfactory system. The present study discloses that serotonin (5-HT) produces excitatory modulation of external tufted (ET) cells, a pivotal neuron in the operation of glomerular circuits. The modulation is due to a transient receptor potential (TRP) channel-mediated inward current induced by activation of 5-HT(2A) receptors. This current produces membrane depolarization and increased bursting frequency in ET cells. Interestingly, the magnitude of the inward current and increased bursting inversely correlate with ET cell spontaneous (intrinsic) bursting frequency: slower bursting ET cells are more strongly modulated than faster bursting cells. Serotonin thus differentially impacts ET cells such that the mean bursting frequency of the population is increased. This centrifugal modulation could impact odor processing by: 1) increasing ET cell excitatory drive on inhibitory neurons to increase presynaptic inhibition of olfactory sensory inputs and postsynaptic inhibition of mitral/tufted cells; and/or 2) coordinating ET cell bursting with exploratory sniffing frequencies (5-8 Hz) to facilitate odor coding.