Neurons In Prefrontal Cortex Research Articles

The β2V287L nicotinic subunit linked to sleep-related epilepsy differently affects fast-spiking and regular spiking somatostatin-expressing neurons in murine prefrontal cortex.

Mutant subunits of the neuronal nicotinic ACh receptor (nAChR) can cause Autosomal Dominant Sleep-related Hypermotor Epilepsy (ADSHE), characterized by frontal seizures during non-rapid eye movement (NREM) sleep. We studied the cellular bases of the pathogenesis in brain slices from mice conditionally expressing the ADSHE-linked β2V287L nAChR subunit. β2V287L mice displayed minor structural alterations, except for a ~10% decrease of prefrontal cortex thickness. However, they showed a substantial decrease of the excitatory input to layer V fast-spiking (FS) interneurons, despite a concomitant increase in the number of glutamatergic terminals around the cell soma. Hence, prefrontal hyperexcitability may depend on a permanent impairment of surround inhibition. The effect disappeared when β2V287L was silenced until postnatal day 15th, suggesting that the transgene selectively affects the maturation of glutamatergic synapses on FS neurons. The other main population of interneurons in layer V was constituted by somatostatin-expressing regular spiking cells. When tested with 10µM nicotine, these displayed larger somatic nicotinic currents in transgenic mice. Thus, during wakefulness, activation of β2V287L-containing nAChRs by the high cholinergic tone may counteract hyperexcitability by promoting local inhibition by somatostatin-expressing cells and decreasing the effect of glutamatergic deficit in FS neurons. This interpretation was tested in networks disinhibited by 2μM bicuculline. Slices expressing β2V287L were more susceptible to develop synchronized activity in the absence of nicotine. Addition of the drug boosted excitability in the controls, but had little effect in β2V287L. Our findings suggest why NREM sleep favors ADSHE seizures and nicotine can be palliative in patients.

Comparison of Golgi-Cox and Intracellular Loading of Lucifer Yellow for Dendritic Spine Density and Morphology Analysis in the Mouse Brain

Dendritic spines are small protrusions on dendrites that serve as the postsynaptic site of the majority of excitatory synapses. These structures are important for normal synaptic transmission, and alterations in their density and morphology have been documented in various disease states. Over 130 years ago, Ramón y Cajal used Golgi-stained tissue sections to study dendritic morphology. Despite the array of technological advances, including iontophoretic microinjection of Lucifer yellow (LY) fluorescent dye, Golgi staining continues to be one of the most popular approaches to visualize dendritic spines. Here, we compared dendritic spine density and morphology among pyramidal neurons in layers 2/3 of the mouse medial prefrontal cortex (mPFC) and pyramidal neurons in hippocampal CA1 using three-dimensional digital reconstructions of (1) brightfield microscopy z-stacks of Golgi-impregnated dendrites and (2) confocal microscopy z-stacks of LY-filled dendrites. Analysis of spine density revealed that the LY microinjection approach enabled detection of approximately three times as many spines as the Golgi staining approach in both brain regions. Spine volume measurements were larger using Golgi staining compared to LY microinjection in both mPFC and CA1. Spine length was mostly comparable between techniques in both regions. In the mPFC, head diameter was similar for Golgi staining and LY microinjection. However, in CA1, head diameter was approximately 50% smaller on LY-filled dendrites compared to Golgi staining. These results indicate that Golgi staining and LY microinjection yield different spine density and morphology measurements, with Golgi staining failing to detect dendritic spines and overestimating spine size.

Bacterial Butyrate in Parkinson's Disease Is Linked to Epigenetic Changes and Depressive Symptoms.

BackgroundThe gut microbiome and its metabolites can impact brain health and are altered in Parkinson's disease (PD) patients. It has been recently demonstrated that PD patients have reduced fecal levels of the potent epigenetic modulator butyrate and its bacterial producers.ObjectivesHere, we investigate whether the changes in the gut microbiome and associated metabolites are related to PD symptoms and epigenetic markers in leucocytes and neurons.MethodsStool, whole blood samples, and clinical data were collected from 55 PD patients and 55 controls. We performed DNA methylation analysis on whole blood samples and analyzed the results in relation to fecal short‐chain fatty acid concentrations and microbiota composition. In another cohort, prefrontal cortex neurons were isolated from control and PD brains. We identified genome‐wide DNA methylation by targeted bisulfite sequencing.ResultsWe show that lower fecal butyrate and reduced counts of genera Roseburia, Romboutsia, and Prevotella are related to depressive symptoms in PD patients. Genes containing butyrate‐associated methylation sites include PD risk genes and significantly overlap with sites epigenetically altered in PD blood leucocytes, predominantly neutrophils, and in brain neurons, relative to controls. Moreover, butyrate‐associated methylated‐DNA regions in PD overlap with those altered in gastrointestinal (GI), autoimmune, and psychiatric diseases.ConclusionsDecreased levels of bacterially produced butyrate are related to epigenetic changes in leucocytes and neurons from PD patients and to the severity of their depressive symptoms. PD shares common butyrate‐dependent epigenetic changes with certain GI and psychiatric disorders, which could be relevant for their epidemiological relation. © 2022 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society

Synthetic Heparan Sulfate Hydrogels Regulate Neurotrophic Factor Signaling and Neuronal Network Activity.

Three-dimensional (3D) synthetic heparan sulfate (HS) constructs possess promising attributes for neural tissue engineering applications. However, their sulfation-dependent ability to facilitate molecular recognition and cell signaling has not yet been investigated. We hypothesized that fully sulfated synthetic HS constructs (bearing compound 1) that are functionalized with neural adhesion peptides will enhance fibroblast growth factor-2 (FGF2) binding and complexation with FGF receptor-1 (FGFR1) to promote the proliferation and neuronal differentiation of human neural stem cells (hNSCs) when compared to constructs with unsulfated controls (bearing compound 2). We tested this hypothesis in vitro using 2D and 3D substrates consisting of different combinations of HS tetrasaccharides (compounds 3 and 4) and an engineered integrin-binding chimeric peptide (CP), which were assembled using strain-promoted alkyne-azide cycloaddition (SPAAC) chemistry. Results indicated that the adhesion of hNSCs increased significantly when cultured on 2D glass substrates functionalized with chimeric peptide. hNSCs encapsulated in 1-CP hydrogels and cultured in media containing the mitogen FGF2 exhibited significantly higher neuronal differentiation when compared to hNSCs in 2-CP hydrogels. These observations were corroborated by Western blot analysis, which indicated the enhanced binding and retention of both FGF2 and FGFR1 by 1 as well as downstream phosphorylation of extracellular signal-regulated kinases (ERK1/2) and enhanced proliferation of hNSCs. Lastly, calcium activity imaging revealed that both 1 and 2 hydrogels supported the neuronal growth and activity of pre-differentiated human prefrontal cortex neurons. Collectively, these results demonstrate that synthetic HS hydrogels can be tailored to regulate growth factor signaling and neuronal fate and activity.

The Distinct Characteristics of Somatostatin Neurons in the Human Brain.

Somatostatin cells are frequently described as a major population of GABAergic neurons in the cerebral cortex. In this study, we performed a comprehensive analysis of their molecular expression, morphological features, and laminar distribution. We provided a detailed description of somatostatin neurons in the human prefrontal cortex, including their proportion in the total neuron population, laminar distribution, neurotransmitter phenotype, as well as their molecular and morphological characteristics using immunofluorescence and RNAscope in situ hybridization. We found that somatostatin neurons comprise around 7% of neocortical neurons in the human Brodmann areas 9 and 14r, without significant difference between the two regions. Somatostatin cells were NeuN positive and synthesized vesicular GABA transporter and glutamate decarboxylase 1 and 2, confirming their neuronal nature and GABAergic phenotype. Somatostatin cells in the upper cortical layers were small, had a high expression of somatostatin mRNA, a relatively low expression of somatostatin peptide, and co-expressed calbindin. In the lower cortical layers, somatostatin cells were larger with complex somato-dendritic morphology, typically showed a lower expression of somatostatin mRNA and a high expression of somatostatin peptide, and co-expressed neuronal nitric oxide synthase (nNOS) and neuropeptide Y (NPY), but not calbindin. Somatostatin neurons in the white matter co-expressed MAP2. Based on their somato-dendritic morphology, cortical somatostatin neurons could be classified into at least five subtypes. The somatostatin neurons of the human prefrontal cortex show remarkable morphological and molecular complexity, which implies that they have equally complex and distinct functions in the human brain.

Distinct neuronal excitability alterations of medial prefrontal cortex in early-life neglect model of rats.

ObjectEarly‐life neglect has irreversible emotional effects on the central nervous system. In this work, we aimed to elucidate distinct functional neural changes in medial prefrontal cortex (mPFC) of model rats.MethodsMaternal separation with early weaning was used as a rat model of early‐life neglect. The excitation of glutamatergic and GABAergic neurons in rat mPFC was recorded and analyzed by whole‐cell patch clamp.ResultsGlutamatergic and GABAergic neurons of mPFC were distinguished by typical electrophysiological properties. The excitation of mPFC glutamatergic neurons was significantly increased in male groups, while the excitation of mPFC GABAergic neurons was significant in both female and male groups, but mainly in terms of rest membrane potential and amplitude, respectively.ConclusionsGlutamatergic and GABAergic neurons in medial prefrontal cortex showed different excitability changes in a rat model of early‐life neglect, which can contribute to distinct mechanisms for emotional and cognitive manifestations.

P.161 Spatiotemporal dynamics of neuronal ensembles in the primate prefrontal cortex during virtual reality navigation tasks

Background: Brain-machine-interface research has utilized multichannel single neuron recordings to decode movement intention. However, the prefrontal cortex (PFC) contains mental representations of more abstract task and goal elements which may be utilized as important signals in a brain-machine-interface. We therefore utilized virtual reality to simulate a real-world task while recording from ensembles of primate PFC neurons. Methods: Two male rhesus macaques (macaca mulatta) were trained to navigate a virtual reality environment using a joystick and learn a context-object association rule. We implanted each monkey with two 96-channel Utah arrays (Blackrock Microsystems) in the lateral PFC (areas 9/46 and 8a) and simultaneously recorded from multiple single neurons. Results: A linear support-vector-machine decoded task elements (context, target location and chosen direction of movement) with significantly greater than chance accuracy. This information was decoded in a sequential manner as the primates made a rule-based decision, with context information appearing first, followed by target location, and chosen side. Conclusions: We found that different neuronal ensembles encode the elements needed for implementing the context rule, and that such ensembles are activated sequentially. Brain-machine-interface systems may benefit by integrating neural data from the PFC, providing salient goal-related information such as the content of the goal and its spatial location.

Transcriptomic Profiling Reveals Discrete Poststroke Dementia Neuronal and Gliovascular Signatures

Poststroke dementia (PSD) is associated with pathology in frontal brain regions, in particular dorsolateral prefrontal cortex (DLPFC) neurons and white matter, remote from the infarct. We hypothesised that PSD results from progressive DLPFC neuronal damage, associated with frontal white matter gliovascular unit (GVU) alterations. We investigated the transcriptomic profile of the neurons and white matter GVU cells previously implicated in pathology. Laser-capture microdissected neurons, astrocytes and endothelial cells were obtained from the Cognitive Function After Stroke cohort of control, PSD and poststroke non-dementia (PSND) human subjects. Gene expression was assessed using microarrays and pathway analysis to compare changes in PSD with controls and PSND. Neuronal findings were validated using NanoString technology and compared with those in the bilateral common carotid artery stenosis (BCAS) mouse model. Comparing changes in PSD compared to controls with changes in PSND compared to controls identified transcriptomic changes associated specifically with dementia. DLPFC neurons showed defects in energy production (tricarboxylic acid (TCA) cycle, adenosine triphosphate (ATP) binding and mitochondria), signalling and communication (MAPK signalling, Toll-like receptor signalling, endocytosis). Similar changes were identified in neurons isolated from BCAS mice. Neuronal findings accompanied by altered astrocyte communication and endothelium immune changes in the frontal white matter, suggesting GVU dysfunction. We propose a pathogenic model in PSD whereby neuronal changes are associated with frontal white matter GVU dysfunction leading to astrocyte failure in supporting neuronal circuits resulting in delayed cognitive decline associated with PSD. Therefore, targeting these processes could potentially ameliorate the dementia seen in PSD.

NLRP3-Dependent Pyroptosis: A Candidate Therapeutic Target for Depression.

Depression, a major public health problem, imposes a significant economic burden on society. Recent studies have gradually unveiled the important role of neuroinflammation in the pathogenesis of depression. Pyroptosis, a programmed cell death mediated by Gasdermins (GSDMs), is also considered to be an inflammatory cell death with links to inflammation. Pyroptosis has emerged as an important pathological mechanism in several neurological diseases and has been found to be involved in several neuroinflammatory-related diseases. A variety of chemical agents and natural products have been found to be capable of exerting therapeutic effects by modulating pyroptosis. Studies have shown that depression is closely associated with pyroptosis and the induced neuroinflammation of relevant brain regions, such as the hippocampus, amygdala, prefrontal cortex neurons, etc., in which the nucleotide-binding oligomerization domain-like receptor protein 3 inflammasome plays a crucial role. This article provides a timely review of recent findings on the activation and regulation of pyroptosis in relation to depression.

Estrus cycle-dependent working memory effects of prefrontal cortex corticotropin-releasing factor neurotransmission.

The prefrontal cortex (PFC) supports a diversity of cognitive processes. Impairment in PFC-dependent cognition is associated with multiple psychiatric disorders, including those known to display sex differences. Our ability to treat this impairment is limited, in part due to an incomplete understanding of the neural mechanisms that support PFC-dependent cognition. In previous studies in male rats, we demonstrated that corticotropin-releasing factor (CRF) receptors and neurons in caudal dorsomedial PFC (dmPFC) regulate PFC-dependent working memory. Subcortically, CRF can exert sex-specific actions, a subset of which are ovarian steroid dependent. To date, the cognitive actions of dmPFC CRF neurotransmission in females are unknown. To address this gap, the current studies examined the effects of chemogenetic and pharmacological manipulations of CRF receptors and neurons within the dmPFC of female rats tested in a spatial working memory task. Outside of proestrus, activation of both CRF receptors and neurons in the caudal, but not rostral, dmPFC impaired working memory. Meanwhile, blockade of CRF receptors in the caudal dmPFC or globally in the brain, improved working memory performance, similar to that seen in males. In contrast, these effects were not observed during proestrus. These observations demonstrate that while CRF neurotransmission in the PFC regulates working memory similarly in males and females, these actions are not observed in females when ovarian steroids are at peak levels.

Lack of interferon regulatory factor 3 leads to anxiety/depression-like behaviors through disrupting the balance of neuronal excitation and inhibition in mice

Disrupting the balance of neuronal excitation and inhibition (E/I) is an important pathogenic mechanism of anxiety and depression. Interferon regulatory factor 3 (IRF3) plays a key role in the innate immune response, and activation of IRF3 triggers the expression of type I interferons and downstream interferon-stimulated genes, which are associated with anxiety and depression. However, whether IRF3 participates in the pathogenesis of anxiety/depression by regulating E/I balance remains poorly understood. Here, we reported that global knockout (KO) of IRF3 (IRF3−/−) significantly increased anxiety/depression-like behaviors, but did not affect normal spatial learning and memory. Compared with wild type (WT) control mice, the E/I balance was disrupted, as reflected by enhanced glutamatergic transmission and decreased GABAergic transmission in the neurons of hippocampal CA1 and medial prefrontal cortex (mPFC) in IRF3-KO mice. Importantly, genetic rescue of IRF3 expression by adeno-associated virus (AAV) was sufficient to alleviate anxiety/depression-like behaviors and restore the neuronal E/I balance in IRF3-KO mice. Taken together, our results indicate that IRF3 is critical in maintaining neuronal E/I balance, thereby playing an essential role in ensuring emotional stability.

Heat shock protein Grp78/BiP/HspA5 binds directly to TDP-43 and mitigates toxicity associated with disease pathology

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease with no cure or effective treatment in which TAR DNA Binding Protein of 43 kDa (TDP-43) abnormally accumulates into misfolded protein aggregates in affected neurons. It is widely accepted that protein misfolding and aggregation promotes proteotoxic stress. The molecular chaperones are a primary line of defense against proteotoxic stress, and there has been long-standing interest in understanding the relationship between chaperones and aggregated protein in ALS. Of particular interest are the heat shock protein of 70 kDa (Hsp70) family of chaperones. However, defining which of the 13 human Hsp70 isoforms is critical for ALS has presented many challenges. To gain insight into the specific Hsp70 that modulates TDP-43, we investigated the relationship between TDP-43 and the Hsp70s using proximity-dependent biotin identification (BioID) and discovered several Hsp70 isoforms associated with TDP-43 in the nucleus, raising the possibility of an interaction with native TDP-43. We further found that HspA5 bound specifically to the RNA-binding domain of TDP-43 using recombinantly expressed proteins. Moreover, in a Drosophila strain that mimics ALS upon TDP-43 expression, the mRNA levels of the HspA5 homologue (Hsc70.3) were significantly increased. Similarly we observed upregulation of HspA5 in prefrontal cortex neurons from human ALS patients. Finally, overexpression of HspA5 in Drosophila rescued TDP-43-induced toxicity, suggesting that upregulation of HspA5 may have a compensatory role in ALS pathobiology.

Systemic administration of lipopolysaccharide induces hyperexcitability of prelimbic neurons via modulation of sodium and potassium currents

In C57BL/6 J mice, systemic inflammation was induced by administering bacterial LPS (1 mg/kg) intraperitoneally. In response, animals exhibited hypokinesia, piloerection, and a slight decrease in body temperature accompanied by increased serum levels of the proinflammatory cytokine TNF-α. 24 h after the immunogenic challenge, acute cortical slices were prepared, and whole-cell patch-clamp recordings were performed in morphologically identified prelimbic neurons of the mice’s prefrontal cortex. Electrophysiologic alterations included changes in the kinetics parameters of the fast-inactivating sodium and slow-inactivating potassium currents. In current-clamp mode, our recordings revealed alterations in several conductances that shape the intrinsic excitability of prelimbic neurons. The action potential exhibited changes in latency, amplitude, and the rheobase current to elicit firing discharge. Likewise, phase plots of the action potentials uncovered alterations in the repetitive firing of prelimbic neurons. Consistent with these changes, the afterhyperpolarization conductance and the slowly decaying, calcium‐dependent after-hyperpolarization current that follows an action potential were decreased in response to systemic LPS. Our data demonstrate that immune activation alters the ionic currents that shape the intrinsic excitability and predicts dysregulation of non-synaptic forms of neuronal plasticity modulated by the intrinsic excitability of prefrontal cortex neurons.

A Preliminary Quantitative Electron Microscopic Analysis Reveals Reduced Number of Mitochondria in the Infralimbic Cortex of Rats Exposed to Chronic Mild Stress.

Exposure to severe, uncontrollable and long-lasting stress is a strong risk factor for the development of numerous mental and somatic disorders. Animal studies document that chronic stress can alter neuronal morphology and functioning in limbic brain structures such as the prefrontal cortex. Mitochondria are intracellular powerhouses generating chemical energy for biochemical reactions of the cell. Recent findings document that chronic stress can lead to changes in mitochondrial function and metabolism. Here, we studied putative mitochondrial damage in response to chronic stress in neurons of the medial prefrontal cortex. We performed a systematic quantitative ultrastructural analysis to examine the consequences of 9-weeks of chronic mild stress on mitochondria number and morphology in the infralimbic cortex of adult male rats. In this preliminary study, we analyzed 4,250 electron microscopic images and 67000 mitochondria were counted and examined in the brains of 4 control and 4 stressed rats. We found significantly reduced number of mitochondria in the infralimbic cortex of the stressed animals, but we could not detect any significant alteration in mitochondrial morphology. These data support the concept that prolonged stress can lead to mitochondrial loss. This in turn may result in impaired energy production. Reduced cellular energy may sensitize the neurons to additional injuries and may eventually trigger the development of psychopathologies.

A sex‐specific role for long noncoding RNA in depression susceptibility and resilience

Major depressive disorder is a common, chronic, and debilitating disorder. Depression strikes women twice more than men, yet the molecular mechanisms contributing to this sex difference are poorly understood. Epigenetic processes that mediate interactions between genetic predispositions and stressful life experiences are known to play a critical role in depression risk. Here, we explored the roles of long noncoding RNAs (lncRNAs), a novel class of epigenetic regulators that are enriched in the primate brain, in depression in both sexes. To that end, we integrated cutting‐edge molecular, bioinformatics, behavioral, and physiological approaches spanning both humans and mice. We found that lncRNAs are robustly regulated in a sex‐specific manner in postmortem brain tissue from depressed humans compared to healthy controls. Utilizing a genome‐wide “guilt‐by‐association” bioinformatics approach, we identified sex‐specific lncRNAs linked to depression. One of these targets, LINC00473, is neuronal‐enriched and is specifically downregulated in the prefrontal cortex of depressed females only. To determine a causal role for LINC00473 in depression, we virally expressed it in mice of both sexes’ prefrontal cortex neurons followed by a behavioral examination. This manipulation mirrored the human sex‐specific phenotype, as expressing LINC00473 induced stress resilience in females only, which was accompanied by changes in synaptic function and gene expression. Another lncRNA we identified (RP11‐298D21.1) is upregulated in the depressed female brain, and therefore we named it FEDORA (FEmale DepressiOn lncRnA). FEDORA is expressed in oligodendrocytes and neurons; thus, we utilized a cell type‐specific viral expression system to test its role in both cell types. We found that expressing FEDORA promoted depression‐like behaviors only in female mice in both cell types. However, these behavioral changes were associated with cell‐type‐specific transcriptional changes, as well as altered electrophysiological and morphological features. Finally, we found that circulating FEDORA levels reflect its brain expression profile: blood FEDORA levels are elevated only in depressed women, suggesting FEDORA as a potential sex‐specific biomarker for a depression diagnosis. Together, this work establishes that lncRNAs play a key role in depression and contribute to the sex differences of this disorder. These findings provide a new view of molecular adaptations contributing to depression risk and point to promising targets for developing novel depression diagnosis and treatment tools.

AT1R‐mediated neurodegeneration is part of the etiology of hypertension‐associated cognitive impairment

Hypertension has now been closely associated to cognitive impairment, due to its contribution to cerebrovascular dysfunction. To investigate whether there is neuronal mechanism, hypertension was induced in C57BL/6j male mice (6 months) by DOCA‐salt treatment (1.5 mg/g, s.c., 28 days). Firstly, behavioral study, which contains object location behavioral task, novel object recognition, Barnes maze, and nesting score test, was performed to assess cognitive function, meanwhile, blood pressure (BP) was monitored by tail‐cuff device. In NT (non‐transgenic) mice, DOCA+1%NaCl increases BP significantly, before vs. after DOCA (systolic BP): 114.8 ±0.94 vs. 133.7 ±3.3 mmHg. In whole, compared to sham controls, the treated NT mice performed worse in all four behavioral tests, indicating cognition decline after DOCA‐salt treatment. Later, brain tissues were collected to evaluate possible degenerative alterations in neurons by transmission electron microscope (TEM) imaging, Golgi‐Cox staining, fluorescence‐activated cell sorting (FACS) and qRT‐PCR. It was shown via the TEM that DOCA‐salt hypertension induces mitochondrial damage and morphological changes in prefrontal cortical neurons, meanwhile, Golgi‐Cox staining revealed decreased numbers of dendritic spines, suggesting the onset of neurodegeneration in DOCA‐salt hypertension. In both prefrontal cortex and hippocampus, the mRNA levels of BDNF (brain‐derived neurotrophic factor) and PI4KIIIβ (phosphatidylinositol 4‐kinase IIIβ) were found to be significantly lower in hypertensive NT mice. Using FACS, neurons were sorted from those regions, then analyzed via qRT‐PCR, which identified that the downregulated expression of PI4KIIIβ takes place in neurons. Using laser speckle contrast imaging system, we detected only decreased functional hyperemia, but no impairment in basal cerebral blood flow of the hypertensive mice, suggesting that the neurodegeneration is not caused by cerebral ischemia. We previously demonstrated that neuronal angiotensin type 1 receptors (AT1R) plays a pivotal role in the maintenance of neurogenic hypertension, and here we hypothesized that activation of AT1R could also exacerbate hypertension‐induced reduction in neuronal function. Particularly, in the hippocampal CA1 of adult mice, treatment of angiotensin II (Ang‐II, 500 nM, bath application) induces a significant inhibition in the induction of long‐term potentiation (LTP), while pre‐treatment with losartan (5 μM, 15 min), the AT1R antagonist, can efficiently block this Ang‐II‐induced inhibition, supporting the involvement of neuronal AT1R. Indeed, in mice with selective deletion of neuronal AT1aR, DOCA‐salt‐induced neurodegeneration was attenuated, as evidenced by significantly higher mRNA levels of cortical BDNF and PI4KIIIβ, compared with the NT. In summary, our data suggest that neuron‐expressing AT1R participates in the development of hypertension‐associated cognitive impairment, independently of vascular AT1R.

Differential Effects of the Lateral Hypothalamus Lesion as an Origin of Orexin and Blockade of Orexin-1 Receptor in the Orbitofrontal Cortex and Anterior Cingulate Cortex on Their Neuronal Activity.

Introduction: Several studies have demonstrated that orexins may regulate different forms of affective and cognitive processes during wakefulness. The Orbitofrontal Cortex (OFC) and Anterior Cingulate Cortex (ACC), as an essential part of the Prefrontal Cortex (PFC), have a crucial role in cognitive processes such as reward and decision-making. They also have a high amount of orexin receptor type 1 (OX1Rs). In the present study, we inhibited OX1Rs in this area after a 10-min baseline recording to find out the role of OX1Rs in the OFC neuron's firing rate. Next, we inhibited the lateral hypothalamus (LH) as the primary source of orexinergic neurons. Afterward, using a single-unit recording technique in rats, we detected the effects of the lateral hypothalamus on the firing rate and activity pattern of the ACC or OFC neurons. Data showed that the blockade of OX1Rs in the OFC could excite 8 and inhibit 1 neuron(s) out of 11. In addition, the blockade of OX1Rs in the ACC could excite 6 and inhibit 3 neurons out of 10. LH inactivation excited 5 out of 12 neurons and inhibited 6 in the ACC. It also excited 8 and inhibited 6 neurons out of 14 in the OFC. These data suggest that the blockade of OX1Rs excites 72% of the neurons, but LH inactivation had a stimulating effect on only 50% of neurons in two main subregions of the PFC. Accordingly, PFC neurons may receive the orexinergic inputs from the LH and indirectly from other sources. Blockade of orexin receptors 1 in ACC alter neural activity in this region.Blockade of orexin receptors 1 in OFC alter neural activity in this region.Lateral hypothalamus inhibition increase neural activity of only 50% neurons in ACC and OFC. The discovery of the neuropeptide orexin/hypocretin in 1998 and subsequent research during the past 20 years revealed an important role for the lateral hypothalamus (LH) in driving the reward pathway, sleep and awake circuits, decision making and psychotic disorders. But our knowledge towards the function of this neurotransmitter on neural activity in specific areas of the brain is limited. In this study we decided to clear the specific role of orexin receptors placed in the two crucial areas of medial prefrontal cortex (mPFC) and the orexin projections from LH on neural firing rates in those regions. In the present study, we investigated the following items by using an in vivo extracellular single-unit recording technique in rats and our data shown that the effect of blocking of orexin receptors1 in mPFC caused a different results than inhibition of the origin of orexin projection in LH as a source of it.

Prefrontal Input to the Periaqueductal Gray Controls Placebo Analgesia

Placebo analgesia is associated with activity in a highly interconnected neural network distributed throughout the brain. However, this is based on a large body of functional imaging work that primarily relies on correlative measures of neural activity and neurochemical signaling obtained in human subjects, making it challenging to ascribe causal roles to the underlying neural pathways. To address this gap, we developed a mouse model of placebo analgesia and used chemogenetic loss-of-function manipulations to identify the underlying neural circuits. We specifically addressed the role of the descending pain modulatory system (DPMS) and its upstream cortical circuits. We found that chemogenetic inactivation of a subpopulation of excitatory neurons in the ventrolateral periaqueductal gray (vlPAG) abolishes both morphine analgesia and morphine-conditioned placebo analgesia. Placebo, but not morphine analgesia, depends on vlPAG-projecting neurons in the medial prefrontal cortex (mPFC) and anterior cingulate cortex (ACC), but not the anterior insula (AI). For placebo to occur, mPFC-to-vlPAG neurons must be active during conditioning, consistent with a critical role for activity-dependent plasticity in this pathway. Our findings suggest that the vlPAG implements cognitive pain modulation by integrating top-down commands, at least some of which are conveyed directly from the cortex. Grant support from Rita Allen Foundation (non-profit) NIDA grant (R00 DA 034648) Klingenstein-Simons Foundation (non-profit).

Gastrointestinal mechanosensation affects the activity of prefrontal cortical neurons mediating social behavior in mice

Social cognition requires integration of sensory modalities with emotion and experience to plan and engage in appropriate social behavior. Oxytocin is a neuropeptide that shapes the perception of social stimuli by activating the oxytocin receptor (Oxtr). Neurons within the medial prefrontal cortex (mPFC) that express Oxtr(s) (referred to as mPFCOxtr) integrate these complex systems. Oxytocin acts within the brain to influence the perception of the external environment; however, Oxtr(s) are also expressed on vagal sensory afferents, suggesting that oxytocin may also influence interoception or the ability to sense one’s internal state. To better understand the role of interoception in social cognition, we examined the structure and function of the neurons within the nodose ganglia that express the Oxtr (referred to as NDGOxtr). To visualize NDGOxtr, we bilaterally injected Cre‐inducible adeno‐associated virus (AAV) synthesizing mCherry or tdTomato into the nodose ganglia (NDG) of mice with Cre‐recombinase directed to the Oxtr gene (Oxtr‐Cre mice). We found that NDGOxtr expressed mRNAs for the mechanically gated ion channels, Piezo 1/2, and sent fibers to the stomach and duodenum that formed intramuscular arrays or intraganglionic laminar endings. These results suggest that NDGOxtr function as mechanoreceptors that detect distention of the gastrointestinal tract. Next, we used in vivo Ca2+ imaging to determine the effect that gastric distention has on mPFCOxtr that mediate social behavior. Oxtr‐Cre mice were delivered Cre‐inducible AAV expressing the fluorescent Ca2+ indicator, GCaMPf, into the mPFC, and subsequently, implanted with a GRIN lens. After habituation to the head mounted miniscope, mice were tested in the social interaction paradigm and Ca2+ events were recorded. Receiver operating characteristic analysis revealed that ≍30% of mPFCOxtr couple firing to social interaction. Next, we evaluated how gastric distention may influence the activity of mPFCOxtr. Mice were given a sham gavage or a gavage of methylcellulose and Ca2+ events from mPFCOxtr were recorded. Differences in Ca2+ events were calculated using a Wilcoxon rank sum test to the classify individual neurons as inhibited, excited, or unchanged by the stimulus. Intriguingly, gavage of methylcellulose robustly inhibited mPFCOxtr relative to the sham‐treated control. To determine whether NDGOxtrmediate this inhibition, Oxtr‐Cre mice outfitted for in vivo Ca2+ imaging were given Cre‐inducible AAV expressing channelrhodopsin2 into the NDG and a fiber optic was implanted into the nucleus of the solitary tract (NTS). This approach enables optogenetic excitation of axons in the NTS originating from NDGOxtr during simultaneous Ca2+ imaging of mPFCOxtr. Preliminary results indicate that optogenetic excitation of NDGOxtr also inhibit mPFCOxtr. Collectively, our results suggest that mechanosensation of the gastrointestinal tract may have a profound influence over the perception of social stimuli.

Alterations of Intrinsic Prefrontal Circuitry in Adolescence and Through Deep-Brain Stimulation in a Nonhuman Primate Model

The intrinsic connectivity of prefrontal cortical neurons changes markedly in adolescence and excessively or abnormally in psychopathology that emerges in early adulthood. We address these processes in a non-human primate model that allows us to interrogate connections between neurons at different developmental stages and to apply deep brain stimulation as a means of altering prefrontal connectivity.