SST Neurons Research Articles

Disinhibition of somatostatin interneurons confers resilience to stress in male but not female mice

Chronic stress represents a vulnerability factor for anxiety and depressive disorders and has been widely used to model aspects of these disorders in rodents. Disinhibition of somatostatin (SST)-positive GABAergic interneurons in mice by deletion of γ2 GABAA receptors selectively from these cells (SSTCre:γ2f/f mice) has been shown to result in behavioral and biochemical changes that mimic the responses to antidepressant doses of ketamine. Here we explored the extent to which SSTCre:γ2f/f mice exhibit resilience to unpredictable chronic mild stress (UCMS). We found that male SSTCre:γ2f/f mice are resilient to UCMS-induced (i) reductions in weight gain, (ii) reductions in SST-immuno-positive cells in medial prefrontal cortex (mPFC), (iii) increases in phosphorylation of eukaryotic elongation factor 2 (eEF2) in mPFC, and (iv) increased anxiety in a novelty suppressed feeding test. Female SSTCre:γ2f/f mice were resilient to UCMS-induced reductions in SST-immuno-positive cells indistinguishably from males. However, in contrast to males, they showed no UCMS effects on weight gain independent of genotype. Moreover, in mPFC of female γ2f/f control mice, UCMS resulted in paradoxically reduced p-EF2 levels without stress effects in the SSTCre:γ2f/f mutants. Lastly, female SSTCre:γ2f/f mice showed increased rather than reduced UCMS induced anxiety compared to γ2f/f controls. Thus, disinhibition of SST interneurons results in behavioral resilience to UCMS selectively in male mice, along with cellular resilience of SST neurons to UCMS independent of sex. Thus, mechanisms underlying vulnerability and resilience to stress are sex specific and map to mPFC rather than hippocampus but appear unrelated to changes in expression of SST as a marker of corresponding interneurons.

1768-P: The Role of Hypothalamic Growth Hormone Receptor–Expressing Neurons in Glucose Metabolism and Energy Homeostasis

GH and the GH receptor (GHR) are present in regions known to participate in the regulation of feeding, energy balance and glucose metabolism, including the hypothalamus. We have previously demonstrated that GHR signals in nutrient-sensing neurons is critical for hepatic glucose production and lipid metabolism. Given the high expression pattern of GHR in the arcuate nucleus (ARC) of the hypothalamus, we aimed to define the specific role of the ARC GHR-expressing neurons in energy homeostasis and glucose metabolism. For this purpose, we have developed a novel GHR cell-specific molecular tool (GHRcre) using CRISPR/Cas9 gene editing technology. We show that GHR+ neurons in the ARC are mostly co-localized with AgRP, GHRH, and SST neurons and rapidly respond to fasting. Specific chemogenetic activation of GHR+ neurons in the ARC (ARCGHR+) by the DREADDs technique impaired glucose metabolism, suggesting the role of these neurons in metabolic homeostasis. Additionally, while activation of ARCGHR+ neurons increased energy homeostasis (RER, VO2) under metabolic resting phase, the responses to fasting were significantly attenuated, demonstrating the inhibitory role of GHR+ neurons in the ARC for fasting responses. Sirtuin 1 (SIRT1) is highly expressed in the ARC and had been associated with hypothalamic responses to fasting. The majority of ARCGHR+ neurons express SIRT1 and respond to fasting by upregulating the SIRT1 expression. Importantly, hypothalamic upregulation of SIRT1 in response to fasting is blunted in mice lacking GHR in AgRP neurons (AgRPEYFP∆GHR mice), suggesting a novel role of SIRT1 within the hypothalamic GH axis and providing evidence for a link between the somatotropic system and SIRT1 function in responses to fasting. Disclosure J. Lima: None. L.K. Debarba: None. I.T. Ayyar: None. C. Ubah: None. M. Khan: None. H. AlRomdhan: None. M. Alysofi: None. M. Sadagurski: None. Funding American Diabetes Association (1-18-JDF-063 to M.S.); Wayne State University

Forced Abstinence From Alcohol Induces Sex-Specific Depression-Like Behavioral and Neural Adaptations in Somatostatin Neurons in Cortical and Amygdalar Regions.

Forced abstinence (FA) from alcohol has been shown to produce a variety of anxiety- and depression-like symptoms in animal models. Somatostatin (SST) neurons, a subtype of GABAergic neurons found throughout the brain, are a novel neural target with potential treatment implications in affective disorders, yet their role in alcohol use disorders (AUD) remains to be explored. Here, we examined the neuroadaptations of SST neurons during forced abstinence from voluntary alcohol consumption. Following 6 weeks of two-bottle choice alcohol consumption and protracted forced abstinence, male and female C57BL/6J mice exhibited a heightened, but sex-specific, depressive-like behavioral profile in the sucrose preference test (SPT) and forced swim test (FST), without changes in anxiety-like behaviors in the elevated plus maze (EPM) and open field test (OFT). FST-induced cFos expressions in the prefrontal cortex (PFC) and ventral bed nucleus of the stria terminalis (vBNST) were altered in FA-exposed female mice only, suggesting a sex-specific effect of forced abstinence on the neural response to acute stress. SST immunoreactivity in these regions was unaffected by forced abstinence, while differences were seen in SST/cFos co-expression in the vBNST. No differences in cFos or SST immunoreactivity were seen in the lateral central nucleus of the amygdala (CEA) and the basolateral amygdala (BLA). Additionally, SST neurons in female mice displayed opposing alterations in the PFC and vBNST, with heightened intrinsic excitability in the PFC and diminished intrinsic excitability in the vBNST. These findings provide an overall framework of forced abstinence-induced neuroadaptations in these key brain regions involved in emotional regulation and processing.

Distinct roles of parvalbumin- and somatostatin-expressing neurons in flexible representation of task variables in the prefrontal cortex.

A hallmark of the prefrontal cortex (PFC) is flexible representation of task-relevant variables. To investigate roles of different interneuron subtypes in this process, we examined discharge characteristics and inactivation effects of parvalbumin (PV)- and somatostatin (SST)-expressing neurons in the mouse PFC during probabilistic classical conditioning. We found activity patterns and inactivation effects differed between PV and SST neurons: SST neurons conveyed cue-associated quantitative value signals until trial outcome, whereas PV neurons maintained valence signals even after trial outcome. Also, PV, but not SST, neuronal population showed opposite responses to reward and punishment. Moreover, inactivation of PV, but not SST, neurons affected outcome responses and activity reversal of pyramidal neurons. Modeling suggested opposite responses of PV neurons to reward and punishment as an efficient mechanism for facilitating rapid cue-outcome contingency learning. Our results suggest primary roles of mPFC PV neurons in rapid value updating and SST neurons in predicting values of upcoming events.

Genome-Wide Analysis of Differential Gene Expression and Splicing in Excitatory Neurons and Interneuron Subtypes.

Cortical circuit activity is shaped by the parvalbumin (PV) and somatostatin (SST) interneurons that inhibit principal excitatory (EXC) neurons and the vasoactive intestinal peptide (VIP) interneurons that suppress activation of other interneurons. To understand the molecular-genetic basis of functional specialization and identify potential drug targets specific to each neuron subtype, we performed a genome wide assessment of both gene expression and splicing across EXC, PV, SST and VIP neurons from male and female mouse brains. These results reveal numerous examples where neuron subtype-specific gene expression, as well as splice-isoform usage, can explain functional differences between neuron subtypes, including in presynaptic plasticity, postsynaptic receptor function, and synaptic connectivity specification. We provide a searchable web resource for exploring differential mRNA expression and splice form usage between excitatory, PV, SST, and VIP neurons (http://research-pub.gene.com/NeuronSubtypeTranscriptomes). This resource, combining a unique new dataset and novel application of analysis methods to multiple relevant datasets, identifies numerous potential drug targets for manipulating circuit function, reveals neuron subtype-specific roles for disease-linked genes, and is useful for understanding gene expression changes observed in human patient brains.SIGNIFICANCE STATEMENT Understanding the basis of functional specialization of neuron subtypes and identifying drug targets for manipulating circuit function requires comprehensive information on cell-type-specific transcriptional profiles. We sorted excitatory neurons and key inhibitory neuron subtypes from mouse brains and assessed differential mRNA expression. We used a genome-wide analysis which not only examined differential gene expression levels but could also detect differences in splice isoform usage. This analysis reveals numerous examples of neuron subtype-specific isoform usage with functional importance, identifies potential drug targets, and provides insight into the neuron subtypes involved in psychiatric disease. We also apply our analysis to two other relevant datasets for comparison, and provide a searchable website for convenient access to the resource.

Regulation of feeding by somatostatin neurons in the tuberal nucleus

The tuberal nucleus (TN) is a hypothalamic region which is well described in humans but remains poorly defined in rodents. In this paper, the authors demonstrated by specific and sophisticated techniques the role of somatostatin expressing TN (TNSST) neurons in the control of food intake in mice. Interestingly, their results showed the specific role of TNSTT neurons in food intake as compared to SST neurons located in the arcuate nucleus. Furthermore, the authors showed that the appetite-promoting hormone, ghrelin, induced a robust activation of TNSST neurons in both in-vivo and in hypothalamic slices. They then confirmed that specific activation of those neurons by chemogenetic or optogenetic effectors indeed promoted a dramatic food consumption. TNSST neurons project to regions in the hypothalamus which are known to be involved in the control of feeding such as the paraventicular nucleus (PVN). These TNSST neuron promoted feeding by inhibiting downstream neurons.

Extensive Inhibitory Gating of Viscerosensory Signals by a Sparse Network of Somatostatin Neurons.

Integration and modulation of primary afferent sensory information begins at the first terminating sites within the CNS, where central inhibitory circuits play an integral role. Viscerosensory information is conveyed to the nucleus of the solitary tract (NTS) where it initiates neuroendocrine, behavioral, and autonomic reflex responses that ensure optimal internal organ function. This excitatory input is modulated by diverse, local inhibitory interneurons, whose functions are not clearly understood. Here we show that, in male rats, 65% of somatostatin-expressing (SST) NTS neurons also express GAD67, supporting their likely role as inhibitory interneurons. Using whole-cell recordings of NTS neurons, from horizontal brainstem slices of male and female SST-yellow fluorescent protein (YFP) and SST-channelrhodopsin 2 (ChR2)-YFP mice, we quantified the impact of SST-NTS neurons on viscerosensory processing. Light-evoked excitatory photocurrents were reliably obtained from SST-ChR2-YFP neurons (n = 16) and the stimulation-response characteristics determined. Most SST neurons (57%) received direct input from solitary tract (ST) afferents, indicating that they form part of a feedforward circuit. All recorded SST-negative NTS neurons (n = 72) received SST-ChR2 input. ChR2-evoked PSCs were largely inhibitory and, in contrast to previous reports, were mediated by both GABA and glycine. When timed to coincide, the ChR2-activated SST input suppressed ST-evoked action potentials at second-order NTS neurons, demonstrating strong modulation of primary viscerosensory input. These data indicate that the SST inhibitory network innervates broadly within the NTS, with the potential to gate viscerosensory input to powerfully alter autonomic reflex function and other behaviors.SIGNIFICANCE STATEMENT Sensory afferent input is modulated according to state. For example the baroreflex is altered during a stress response or exercise, but the basic mechanisms underpinning this sensory modulation are not fully understood in any sensory system. Here we demonstrate that the neuronal processing of viscerosensory information begins with synaptic gating at the first central synapse with second-order neurons in the NTS. These data reveal that the somatostatin subclass of inhibitory interneurons are driven by visceral sensory input to play a major role in gating viscerosensory signals, placing them within a feedforward circuit within the NTS.

Recruitment of GABAergic Interneurons in the Barrel Cortex during Active Tactile Behavior

Neural computation involves diverse types of GABAergic inhibitory interneurons that are integrated with excitatory (E) neurons into precisely structured circuits. To understand how each neuron type shapes sensory representations, we measured firing patterns of defined types of neurons in the barrel cortex while mice performed an active, whisker-dependent object localization task. Touch excited fast-spiking (FS) interneurons at short latency, followed by activation of E neurons and somatostatin-expressing (SST) interneurons. Touch only weakly modulated vasoactive intestinal polypeptide-expressing (VIP) interneurons. Voluntary whisker movement activated FS neurons in the ventral posteromedial nucleus (VPM) target layers, a subset of SST neurons and a majority of VIP neurons. Together, FS neurons track thalamic input, mediating feedforward inhibition. SST neurons monitor local excitation, providing feedback inhibition. VIP neurons are activated by non-sensory inputs, disinhibiting E and FS neurons. Our data reveal rules of recruitment for interneuron types during behavior, providing foundations for understanding computation in cortical microcircuits.

S212. The Role of Somatostatin Positive Interneurons in the Prelimbic Cortex in Alcohol Consumption

Alcohol Use Disorders (AUDs) and major depressive disorder (MDD) are highly comorbid disorders, both of which are major health and social concerns. Somatostatin (SST) expressing GABAergic interneurons in the forebrain have long been implicated in MDD, though their role in AUDs is currently under investigated. Previous work has shown that artificially increasing the function of SST neurons globally in the brain has antidepressant drug treatment-like consequences. Due to the comorbidity between AUDs and MDDs, we further investigated how SST neurons in the prelimbic cortex are altered following DID-binge like ethanol exposure.

Enhanced responses to somatostatin interneuron activation in developmentally malformed cortex.

SummaryIntractable epilepsy is commonly associated with developmental cortical malformations. Using the rodent freeze lesion model, we have sought the underlying circuit abnormalities contributing to the epileptiform activity that occurs in association with the structural pathology of four‐layered microgyria. We showed previously that within the epileptogenic paramicrogyral region (PMR) surrounding the malformation, non–fast‐spiking neurons commonly containing somatostatin (SSt) exhibit alterations, including having a greater maximum firing rate. Here we examined the output of SSt interneurons with optogenetics, using SSt‐Cre mice mated to mice with floxed channelrhodopsin‐2. Voltage clamp recordings from layer V pyramidal neurons in ex vivo slices had significantly enhanced SSt‐evoked inhibitory postsynaptic currents in PMR cortex compared to control. In addition, under conditions of low‐Mg2+ artificial cerebral spinal fluid (aCSF), light activation of the SSt neurons evoked field potential epileptiform activity in the PMR cortex, but not in control. These data suggest that within the PMR cortex, SSts have a significantly larger effect on excitatory neurons. Surprisingly, the network effect of this enhanced inhibition is hyperexcitability with propagating epileptiform activity, perhaps due to disinhibition of other interneuron cell types or to enhanced synchrony of excitatory cortical elements. This identification creates a new locus for potential modulation of epileptiform activity associated with cortical malformation.

Somatostatin Gene and Protein Expression in the Non-human Primate Central Extended Amygdala

Alterations in central extended amygdala (EAc) function have been linked to anxiety, depression, and anxious temperament (AT), the early-life risk to develop these disorders. The EAc is composed of the central nucleus of the amygdala (Ce), the bed nucleus of the stria terminalis (BST), and the sublenticular extended amygdala (SLEA). Using a non-human primate model of AT and multimodal neuroimaging, the Ce and the BST were identified as key AT-related regions. Both areas are primarily comprised of GABAergic neurons and the lateral Ce (CeL) and lateral BST (BSTL) have among the highest expression of neuropeptides in the brain. Somatostatin (SST) is of particular interest because mouse studies demonstrate that SST neurons, along with corticotropin-releasing factor (CRF) neurons, contribute to a threat-relevant EAc microcircuit. Although the distribution of CeL and BSTL SST neurons has been explored in rodents, this system is not well described in non-human primates. In situ hybridization demonstrated an anterior–posterior gradient of SST mRNA in the CeL but not the BSTL of non-human primates. Triple-labeling immunofluorescence staining revealed that SST protein-expressing cell bodies are a small proportion of the total CeL and BSTL neurons and have considerable co-labeling with CRF. The SLEA exhibited strong SST mRNA and protein expression, suggesting a role for SST in mediating information transfer between the CeL and BSTL. These data provide the foundation for mechanistic non-human primate studies focused on understanding EAc function in neuropsychiatric disorders.

Induction of human somatostatin and parvalbumin neurons by expressing a single transcription factor LIM homeobox 6.

Human GABAergic interneurons (GIN) are implicated in normal brain function and in numerous mental disorders. However, the generation of functional human GIN subtypes from human pluripotent stem cells (hPSCs) has not been established. By expressing LHX6, a transcriptional factor that is critical for GIN development, we induced hPSCs to form GINs, including somatostatin (SST, 29%) and parvalbumin (PV, 21%) neurons. Our RNAseq results also confirmed the alteration of GIN identity with the overexpression of LHX6. Five months after transplantation into the mouse brain, the human GABA precursors generated increased population of SST and PV neurons by overexpressing LHX6. Importantly, the grafted human GINs exhibited functional electrophysiological properties and even fast-spiking-like action potentials. Thus, expression of the single transcription factor LHX6 under our GIN differentiation condition is sufficient to robustly induce human PV and SST subtypes.

Expression of Transcripts Selective for GABA Neuron Subpopulations across the Cortical Visuospatial Working Memory Network in the Healthy State and Schizophrenia.

Visuospatial working memory (WM), which is impaired in schizophrenia, depends on a distributed network including visual, posterior parietal, and dorsolateral prefrontal cortical regions. Within each region, information processing is differentially regulated by subsets of γ-aminobutyric acid (GABA) neurons that express parvalbumin (PV), somatostatin (SST), or vasoactive intestinal peptide (VIP). In schizophrenia, WM impairments have been associated with alterations of PV and SST neurons in the dorsolateral prefrontal cortex. Here, we quantified transcripts selectively expressed in GABA neuron subsets across four cortical regions in the WM network from comparison and schizophrenia subjects. In comparison subjects, PV mRNA levels declined and SST mRNA levels increased from posterior to anterior regions, whereas VIP mRNA levels were comparable across regions except for the primary visual cortex (V1). In schizophrenia subjects, each transcript in PV and SST neurons exhibited similar alterations across all regions, whereas transcripts in VIP neurons were unaltered in any region except for V1. These findings suggest that the contribution of each GABA neuron subset to inhibitory regulation of local circuitry normally differs across cortical regions of the visuospatial WM network and that in schizophrenia alterations of PV and SST neurons are a shared feature across these regions, whereas VIP neurons are affected only in V1.

Loss of Hypothalamic Somatostatin (SST) Contributes to Bone Marrow (BM) Dysfunction and Diabetic Retinopathy (DR) in Type 2 Diabetic Rats

Purpose: Since loss of retinal SST and circulating SST occurs in DR, we asked if loss of hypothalamic SST production would impact the innervation and function of the BM and influence DR in T2D rat model. Methods: Brain sections of BBZ/Wor rats with 4 months of diabetes and age-matched nondiabetic lean BBZ rats were immuno-stained for SST, Iba-1 and Neu-N. To examine the neuronal connection between the BM and pre-sympathetic brainstem and hypothalamic areas, both control and diabetic rats were injected in a blinded manner with GFP-transgenic pseudorabies virus (PRV-152) into their femurs. Four days later rats were euthanized and brain sections prepared for colocalization of GFP with SST. DR was assessed by enumeration of acellular capillaries in trypsin-digested retinas. Results: Injection of PRV into femur showed the presence of active virus in neurons of the paraventricular nucleus of the hypothalamus (PVN), rostral ventrolateral medulla and nucleus tractus solitarius of the brain of control rats. Colocalization studies showed that periventricular hypothalamic SST neurons were also GFP+ and directly innervated the BM. Quantitation showed that diabetic rats had significantly fewer GFP+ neurons in the PVN (n=6, *P<0.05), supporting neuronal loss. SST staining of brain sections showed significant reduction in the number of SST+ cells in diabetic rats (58±5) compared with nondiabetic rats (88±6) (n=6, *P<0.05). The density of Iba-1+ microglia increased, while the NeuN+ neurons decreased in the hypothalamus supporting an increase of regional inflammation and neuronal loss. Diabetic rats showed an increase in acellular capillaries compared to controls (15± 4 vs. 4±1mm2) (p<0.001). Conclusions: These studies support the notion that periventricular hypothalamic SST neurons directly innervate BM and that preservation of this small, but important population is relevant to prevention of diabetes induced-BM dysfunction and development of DR. Disclosure A. Longhini: None. J. Thinschmidt: None. M. Boulton: None. M.A. King: None. M.B. Grant: None.

Activation of axon initial segmental GABAA receptors inhibits action potential generation in neocortical GABAergic interneurons

Ionotropic GABAA receptors expressing at the axon initial segment (AIS) of glutamatergic pyramidal cell (PC) in the cortex plays critical roles in regulating action potential generation. However, it remains unclear whether these receptors also express at the AIS of cortical GABAergic interneurons. In mouse prefrontal cortical slices, we performed experiments at the soma and AIS of the two most abundant GABAergic interneurons: parvalbumin (PV) and somatostatin (SST) positive neurons. Local application of GABA at the perisomatic axonal regions could evoke picrotoxin-sensitive currents with a reversal potential near the Cl− equilibrium potential. Puffing agonists to outside-out patches excised from AIS confirmed the expression of GABAA receptors. Further pharmacological experiments revealed that GABAA receptors in AIS of PV neurons contain α1 subunits, different from those containing α2/3 in AIS and α4 in axon trunk of layer-5 PCs. Cell-attached recording at the soma of PV and SST neurons revealed that the activation of AIS GABAA receptors inhibits the action potential generation induced by synaptic stimulation. Together, our results demonstrate that the AIS of PV and SST neurons express GABAA receptors with distinct subunit composition, which exert an inhibitory effect on neuronal excitability in these inhibitory interneurons.

Transcriptional Profiling of Somatostatin Interneurons in the Spinal Dorsal Horn

The spinal dorsal horn (SDH) is comprised of distinct neuronal populations that process different somatosensory modalities. Somatostatin (SST)-expressing interneurons in the SDH have been implicated specifically in mediating mechanical pain. Identifying the transcriptomic profile of SST neurons could elucidate the unique genetic features of this population and enable selective analgesic targeting. To that end, we combined the Isolation of Nuclei Tagged in Specific Cell Types (INTACT) method and Fluorescence Activated Nuclei Sorting (FANS) to capture tagged SST nuclei in the SDH of adult male mice. Using RNA-sequencing (RNA-seq), we uncovered more than 13,000 genes. Differential gene expression analysis revealed more than 900 genes with at least 2-fold enrichment. In addition to many known dorsal horn genes, we identified and validated several novel transcripts from pharmacologically tractable functional classes: Carbonic Anhydrase 12 (Car12), Phosphodiesterase 11 A (Pde11a), and Protease-Activated Receptor 3 (F2rl2). In situ hybridization of these novel genes showed differential expression patterns in the SDH, demonstrating the presence of transcriptionally distinct subpopulations within the SST population. Overall, our findings provide new insights into the gene repertoire of SST dorsal horn neurons and reveal several novel targets for pharmacological modulation of this pain-mediating population and treatment of pathological pain.

Hyperactivity in mice lacking one allele of the glutamic acid decarboxylase 67 gene.

GABAergic interneuron loss, maturational delay or imbalance of glutamatergic to GABAergic signaling has been implicated in several neuropsychiatric disorders including Tourette syndrome and attention-deficit/hyperactivity disorder (ADHD). In schizophrenia, decreases in parvalbumin (PV), somatostatin (Sst) and glutamic acid decarboxylase (GAD) RNA have been observed and seem to indicate a failure in maturation in PV and Sst neurons. In Tourette syndrome, which has a high level of comorbid ADHD, reduced numbers of parvalbumin expressing neurons have been observed in the basal ganglia of affected patients. In addition, polymorphisms in the GAD1 gene that codes for GAD67 protein have been associated with ADHD. We have examined whether mice with a disrupted Gad67 allele, the Gad67 GFP knock-in mice (Gad67-GFP+/-), display abnormal locomotor behavior or altered anxiety behavior on the elevated plus maze. We found that Gad67-GFP+/- mice displayed a mild hyperactivity compared to control littermates.

Lentiviral vector-mediated somatostatin overexpression suppresses seizures induced in hippocampal kindled rats

Objective To explore the effect of lentiviral vector-mediated somatostatin (SST) expression on seizures induced by hippocampal kindling in rats. Methods Adult Sprague-Dawley rats were randomly divided into the sham group (Sham), epilepsy group (EP), Lenti-pSyn-EGFP (LV-EGFP) group and Lenti-pSyn-SST-2A-EGFP (LV-SST) group.The rats in LV-EGFP group were subsequently electrically hippocampal kindled and LV-EGFP (5 μl) was injected into dentate gyrus (DG). The rats in LV-SST group were kindled and LV-SST (5 μl) was injected into the dentate gyrus (DG), medial entorhinal cortex (MEC) or amygdala (Amy). Seizure severity was evaluated and immunohistochemical staining was employed to detect the expression of SST, neuron specific nuclear protein (NeuN) and microtubule associated protein 2 (MAP2). Results The current values to the first stage V seizure of LV-SST (DG) group, LV-SST (MEC) group or LV-SST (Amy) group ((143.8±3.8)μA, (142.5±4.1)μA, (142.5±5.3) μA, respectively) were significantly increased compared with that of epilepsy (EP) group ((136.3±5.3)μA), and V stage current values of LV-SST groups in each stimulation day were higher than that of EP group except the fifth stimulation day (P<0.05). After kindling, SST expression and NeuN-positive neurons of EP group and LV-SST groups were less than that of Sham group in CA1, CA3 and DG. SST and NeuN neurons loss in LV-SST groups were less than that of EP group (P<0.05) and MAP2 immunohistochemistry stainings in LV-SST groups were higher than that in EP group. Conclusion Lentiviral vector-mediated somatostatin expression suppresses seizures and can rescue the neuronal damage of seizure induced by kindling in hippocampus, which may provide a new method of gene therapy for temporal lobe epilepsy. Key words: Epilepsy; Somatostatin; Hippocampus; Lentivirus; Gene therapy

Age-Related Gene Expression in the Frontal Cortex Suggests Synaptic Function Changes in Specific Inhibitory Neuron Subtypes.

Genome-wide expression profiling of the human brain has revealed genes that are differentially expressed across the lifespan. Characterizing these genes adds to our understanding of both normal functions and pathological conditions. Additionally, the specific cell-types that contribute to the motor, sensory and cognitive declines during aging are unclear. Here we test if age-related genes show higher expression in specific neural cell types. Our study leverages data from two sources of murine single-cell expression data and two sources of age-associations from large gene expression studies of postmortem human brain. We used nonparametric gene set analysis to test for age-related enrichment of genes associated with specific cell-types; we also restricted our analyses to specific gene ontology groups. Our analyses focused on a primary pair of single-cell expression data from the mouse visual cortex and age-related human post-mortem gene expression information from the orbitofrontal cortex. Additional pairings that used data from the hippocampus, prefrontal cortex, somatosensory cortex and blood were used to validate and test specificity of our findings. We found robust age-related up-regulation of genes that are highly expressed in oligodendrocytes and astrocytes, while genes highly expressed in layer 2/3 glutamatergic neurons were down-regulated across age. Genes not specific to any neural cell type were also down-regulated, possibly due to the bulk tissue source of the age-related genes. A gene ontology-driven dissection of the cell-type enriched genes highlighted the strong down-regulation of genes involved in synaptic transmission and cell-cell signaling in the Somatostatin (Sst) neuron subtype that expresses the cyclin dependent kinase 6 (Cdk6) and in the vasoactive intestinal peptide (Vip) neuron subtype expressing myosin binding protein C, slow type (Mybpc1). These findings provide new insights into cell specific susceptibility to normal aging, and suggest age-related synaptic changes in specific inhibitory neuron subtypes.

Behavioral-state modulation of inhibition is context-dependent and cell type specific in mouse visual cortex.

Cortical responses to sensory stimuli are modulated by behavioral state. In the primary visual cortex (V1), visual responses of pyramidal neurons increase during locomotion. This response gain was suggested to be mediated through inhibitory neurons, resulting in the disinhibition of pyramidal neurons. Using in vivo two-photon calcium imaging in layers 2/3 and 4 in mouse V1, we reveal that locomotion increases the activity of vasoactive intestinal peptide (VIP), somatostatin (SST) and parvalbumin (PV)-positive interneurons during visual stimulation, challenging the disinhibition model. In darkness, while most VIP and PV neurons remained locomotion responsive, SST and excitatory neurons were largely non-responsive. Context-dependent locomotion responses were found in each cell type, with the highest proportion among SST neurons. These findings establish that modulation of neuronal activity by locomotion is context-dependent and contest the generality of a disinhibitory circuit for gain control of sensory responses by behavioral state.