Expression of c-fos protein in brain: metabolic mapping at the cellular level

A plastic aggrecan barrier modulated by peripheral energy state gates metabolic signal access to arcuate neurons

The hypothalamic arcuate nucleus (ARH) contains neurons vital for maintaining energy homeostasis that sense and respond to changes in blood-borne metabolic hormones. Despite its juxtaposition to the median eminence (ME), a circumventricular organ lacking a blood-brain barrier and thus exposed to circulating molecules, only a few ventral ARH neurons perceive these extravasating metabolic signals due to a poorly understood ME/ARH diffusion barrier. Here, we show in male mice that aggrecan, a perineural-net proteoglycan deposited by orexigenic ARH neurons, creates a peculiar ventrodorsal diffusion gradient. Fasting enhances aggrecan deposition more dorsally, reinforcing the diffusion barrier, particularly around neurons adjacent to fenestrated capillary loops that enter the ARH. The disruption of aggrecan deposits results in unregulated diffusion of blood-borne molecules into the ARH and impairs food intake. Our findings reveal the molecular nature and plasticity of the ME/ARH diffusion barrier, and indicate its physiological role in hypothalamic metabolic hormone sensing.

Changes in ethanol effects in knock-in mice expressing ethanol insensitive alpha1 and alpha2 glycine receptor subunits

AIMS

Glycine receptors (GlyRs) are potentiated by physiologically relevant concentrations of ethanol, and mutations in the intracellular loop of α1 and α2 subunits reduced the effect of the drug. Knock-in (KI) mice having these individual mutations revealed that α1 and α2 subunits played a role in ethanol-induced sedation and ethanol intake. In this study, we wanted to examine if the effects of stacking both mutations in a 2xKI mouse model (α1/α2) generated by a selective breeding strategy further impacted cellular and behavioral responses to ethanol.

MAIN METHODS

We used electrophysiological recordings to examine ethanol's effect on GlyRs and evaluated ethanol-induced neuronal activation using c-Fos immunoreactivity and the genetically encoded calcium indicator GCaMP6s in the nucleus accumbens (nAc). We also examined ethanol-induced behavior using open field, loss of the righting response, and drinking in the dark (DID) paradigm.

KEY FINDINGS

Ethanol did not potentiate GlyRs nor affect neuronal excitability in the nAc from 2xKI. Moreover, ethanol decreased the Ca2+ signal in WT mice, whereas there were no changes in the signal in 2xKI mice. Interestingly, there was an increase in c-Fos baseline in the 2xKI mice in the absence of ethanol. Behavioral assays showed that 2xKI mice recovered faster from a sedative dose of ethanol and had higher ethanol intake on the first test day of the DID test than WT mice. Interestingly, an open-field assay showed that 2xKI mice displayed less anxiety-like behavior than WT mice.

SIGNIFICANCE

The results indicate that α1 and α2 subunits are biologically relevant targets for regulating sedative effects and ethanol consumption.

Mice with deficiency in Pcdh15, a gene associated with bipolar disorders, exhibit significantly elevated diurnal amplitudes of locomotion and body temperature

Genetic factors significantly affect the pathogenesis of psychiatric disorders. However, the specific pathogenic mechanisms underlying these effects are not fully understood. Recent extensive genomic studies have implicated the protocadherin-related 15 (PCDH15) gene in the onset of psychiatric disorders, such as bipolar disorder (BD). To further investigate the pathogenesis of these psychiatric disorders, we developed a mouse model lacking Pcdh15. Notably, although PCDH15 is primarily identified as the causative gene of Usher syndrome, which presents with visual and auditory impairments, our mice with Pcdh15 homozygous deletion (Pcdh15-null) did not exhibit observable structural abnormalities in either the retina or the inner ear. The Pcdh15-null mice showed very high levels of spontaneous motor activity which was too disturbed to perform standard behavioral testing. However, the Pcdh15 heterozygous deletion mice (Pcdh15-het) exhibited enhanced spontaneous locomotor activity, reduced prepulse inhibition, and diminished cliff avoidance behavior. These observations agreed with the symptoms observed in patients with various psychiatric disorders and several mouse models of psychiatric diseases. Specifically, the hyperactivity may mirror the manic episodes in BD. To obtain a more physiological, long-term quantification of the hyperactive phenotype, we implanted nano tag® sensor chips in the animals, to enable the continuous monitoring of both activity and body temperature. During the light-off period, Pcdh15-null exhibited elevated activity and body temperature compared with wild-type (WT) mice. However, we observed a decreased body temperature during the light-on period. Comprehensive brain activity was visualized using c-Fos mapping, which was assessed during the activity and temperature peak and trough. There was a stark contrast between the distribution of c-Fos expression in Pcdh15-null and WT brains during both the light-on and light-off periods. These results provide valuable insights into the neural basis of the behavioral and thermal characteristics of Pcdh15-deletion mice. Therefore, Pcdh15-deletion mice can be a novel model for BD with mania and other psychiatric disorders, with a strong genetic component that satisfies both construct and surface validity.

Unraveling the Intricacies of OPG/RANKL/RANK Biology and Its Implications in Neurological Disorders-A Comprehensive Literature Review

The OPG/RANKL/RANK framework, along with its specific receptors, plays a crucial role in bone remodeling and the functioning of the central nervous system (CNS) and associated disorders. Recent research and investigations provide evidence that the components of osteoprotegerin (OPG), receptor activator of NF-kB ligand (RANKL), and receptor activator of NF-kB (RANK) are expressed in the CNS. The CNS structure encompasses cells involved in neuroinflammation, including local macrophages, inflammatory cells, and microglia that cross the blood-brain barrier. The OPG/RANKL/RANK trio modulates the neuroinflammatory response based on the molecular context. The levels of OPG/RANKL/RANK components can serve as biomarkers in the blood and cerebrospinal fluid. They act as neuroprotectants following brain injuries and also participate in the regulation of body weight, internal body temperature, brain ischemia, autoimmune encephalopathy, and energy metabolism. Although the OPG/RANKL/RANK system is primarily known for its role in bone remodeling, further exploring deeper into its multifunctional nature can uncover new functions and novel drug targets for diseases not previously associated with OPG/RANKL/RANK signaling.

Claustrum projections to the anterior cingulate modulate nociceptive and pain-associated behavior

The anterior cingulate cortex (ACC) is critical for the perception and unpleasantness of pain.1,2,3,4,5,6 It receives nociceptive information from regions such as the thalamus and amygdala and projects to several cortical and subcortical regions of the pain neuromatrix.7,8 ACC hyperexcitability is one of many functional changes associated with chronic pain, and experimental activation of ACC pyramidal cells produces hypersensitivity to innocuous stimuli (i.e., allodynia).9,10,11,12,13,14 A less-well-studied projection to the ACC arises from a small forebrain region, the claustrum.15,16,17,18,19,20 Stimulation of excitatory claustrum projection neurons preferentially activates GABAergic interneurons, generating feed-forward inhibition onto excitatory cortical networks.21,22,23,24 Previous work has shown that claustrocingulate projections display altered activity in prolonged pain25,26,27; however, it remains unclear whether and how the claustrum participates in nociceptive processing and high-order pain behaviors. Inhibition of ACC activity reverses mechanical allodynia in animal models of persistent and neuropathic pain,1,9,28 suggesting claustrum inputs may function to attenuate pain processing. In this study, we sought to define claustrum function in acute and chronic pain. We found enhanced claustrum activity after a painful stimulus that was attenuated in chronic inflammatory pain. Selective inhibition of claustrocingulate projection neurons enhanced acute nociception but blocked pain learning. Inversely, chemogenetic activation of claustrocingulate neurons had no effect on basal nociception but rescued inflammation-induced mechanical allodynia. Together, these results suggest that claustrocingulate neurons are a critical component of the pain neuromatrix, and dysregulation of this connection may contribute to chronic pain.

Multimodal MRI reveals brainstem connections that sustain wakefulness in human consciousness

Consciousness is composed of arousal (i.e., wakefulness) and awareness. Substantial progress has been made in mapping the cortical networks that underlie awareness in the human brain, but knowledge about the subcortical networks that sustain arousal in humans is incomplete. Here, we aimed to map the connectivity of a proposed subcortical arousal network that sustains wakefulness in the human brain, analogous to the cortical default mode network (DMN) that has been shown to contribute to awareness. We integrated data from ex vivo diffusion magnetic resonance imaging (MRI) of three human brains, obtained at autopsy from neurologically normal individuals, with immunohistochemical staining of subcortical brain sections. We identified nodes of the proposed default ascending arousal network (dAAN) in the brainstem, hypothalamus, thalamus, and basal forebrain. Deterministic and probabilistic tractography analyses of the ex vivo diffusion MRI data revealed projection, association, and commissural pathways linking dAAN nodes with one another and with DMN nodes. Complementary analyses of in vivo 7-tesla resting-state functional MRI data from the Human Connectome Project identified the dopaminergic ventral tegmental area in the midbrain as a widely connected hub node at the nexus of the subcortical arousal and cortical awareness networks. Our network-based autopsy methods and connectivity data provide a putative neuroanatomic architecture for the integration of arousal and awareness in human consciousness.

Essential role of ROS - 8-Nitro-cGMP signaling in long-term memory of motor learning and cerebellar synaptic plasticity

Although reactive oxygen species (ROS) are known to have harmful effects in organisms, recent studies have demonstrated expression of ROS synthases at various parts of the organisms and the controlled ROS generation, suggesting possible involvement of ROS signaling in physiological events of individuals. However, physiological roles of ROS in the CNS, including functional roles in higher brain functions or neuronal activity-dependent ROS production, remain to be elucidated. Here, we demonstrated involvement of ROS - 8-NO2-cGMP signaling in motor learning and synaptic plasticity in the cerebellum. In the presence of inhibitors of ROS signal or ROS synthases, cerebellar motor learning was impaired, and the stimulus inducing long-term depression (LTD), cellular basis for the motor learning, failed to induce LTD but induced long-term potentiation (LTP)-like change at cerebellar synapses. Furthermore, ROS was produced by LTD-inducing stimulus in enzyme-dependent manner, and excess administration of the antioxidant vitamin E impaired cerebellar motor learning, suggesting beneficial roles of endogenous ROS in the learning. As a downstream signal, involvement of 8-NO2-cGMP in motor learning and cerebellar LTD were also revealed. These findings indicate that ROS - 8-NO2-cGMP signal is activated by neuronal activity and is essential for cerebellum-dependent motor learning and synaptic plasticity, demonstrating involvement of the signal in physiological function of brain systems.

An optrode array for spatiotemporally-precise large-scale optogenetic stimulation of deep cortical layers in non-human primates

Optogenetics has transformed studies of neural circuit function, but remains challenging to apply to non-human primates (NHPs). A major challenge is delivering intense, spatiotemporally-precise, patterned photostimulation across large volumes in deep tissue. Such stimulation is critical, for example, to modulate selectively deep-layer corticocortical feedback circuits. To address this need, we have developed the Utah Optrode Array (UOA), a 10×10 glass needle waveguide array fabricated atop a novel opaque optical interposer, and bonded to an electrically addressable µLED array. In vivo experiments with the UOA demonstrated large-scale, spatiotemporally precise, activation of deep circuits in NHP cortex. Specifically, the UOA permitted both focal (confined to single layers/columns), and widespread (multiple layers/columns) optogenetic activation of deep layer neurons, as assessed with multi-channel laminar electrode arrays, simply by varying the number of activated µLEDs and/or the irradiance. Thus, the UOA represents a powerful optoelectronic device for targeted manipulation of deep-layer circuits in NHP models.

A simple and reliable method for claustrum localization across age in mice

The anatomical organization of the rodent claustrum remains obscure due to lack of clear borders that distinguish it from neighboring forebrain structures. Defining what constitutes the claustrum is imperative for elucidating its functions. Methods based on gene/protein expression or transgenic mice have been used to spatially outline the claustrum but often report incomplete labeling and/or lack of specificity during certain neurodevelopmental timepoints. To reliably identify claustrum projection cells in mice, we propose a simple immunolabelling method that juxtaposes the expression pattern of claustrum-enriched and cortical-enriched markers. We determined that claustrum cells immunoreactive for the claustrum-enriched markers Nurr1 and Nr2f2 are devoid of the cortical marker Tle4, which allowed us to differentiate the claustrum from adjoining cortical cells. Using retrograde tracing, we verified that nearly all claustrum projection neurons lack Tle4 but expressed Nurr1/Nr2f2 markers to different degrees. At neonatal stages between 7 and 21 days, claustrum projection neurons were identified by their Nurr1-postive/Tle4-negative expression profile, a time-period when other immunolabelling techniques used to localize the claustrum in adult mice are ineffective. Finally, exposure to environmental novelty enhanced the expression of the neuronal activation marker c-Fos in the claustrum region. Notably, c-Fos labeling was mainly restricted to Nurr1-positive cells and nearly absent from Tle4-positive cells, thus corroborating previous work reporting novelty-induced claustrum activation. Taken together, this method will aid in studying the claustrum during postnatal development and may improve histological and functional studies where other approaches are not amenable.

Regulation of specific abnormal calcium signals in the hippocampal CA1 and primary cortex M1 alleviates the progression of temporal lobe epilepsy

Temporal lobe epilepsy is a multifactorial neurological dysfunction syndrome that is refractory, resistant to antiepileptic drugs, and has a high recurrence rate. The pathogenesis of temporal lobe epilepsy is complex and is not fully understood. Intracellular calcium dynamics have been implicated in temporal lobe epilepsy. However, the effect of fluctuating calcium activity in CA1 pyramidal neurons on temporal lobe epilepsy is unknown, and no longitudinal studies have investigated calcium activity in pyramidal neurons in the hippocampal CA1 and primary motor cortex M1 of freely moving mice. In this study, we used a multi-channel fiber photometry system to continuously record calcium signals in CA1 and M1 during the temporal lobe epilepsy process. We found that calcium signals varied according to the grade of temporal lobe epilepsy episodes. In particular, cortical spreading depression, which has recently been frequently used to represent the continuously and substantially increased calcium signals, was found to correspond to complex and severe behavioral characteristics of temporal lobe epilepsy ranging from grade II to grade V. However, vigorous calcium oscillations and highly synchronized calcium signals in CA1 and M1 were strongly related to convulsive motor seizures. Chemogenetic inhibition of pyramidal neurons in CA1 significantly attenuated the amplitudes of the calcium signals corresponding to grade I episodes. In addition, the latency of cortical spreading depression was prolonged, and the above-mentioned abnormal calcium signals in CA1 and M1 were also significantly reduced. Intriguingly, it was possible to rescue the altered intracellular calcium dynamics. Via simultaneous analysis of calcium signals and epileptic behaviors, we found that the progression of temporal lobe epilepsy was alleviated when specific calcium signals were reduced, and that the end-point behaviors of temporal lobe epilepsy were improved. Our results indicate that the calcium dynamic between CA1 and M1 may reflect specific epileptic behaviors corresponding to different grades. Furthermore, the selective regulation of abnormal calcium signals in CA1 pyramidal neurons appears to effectively alleviate temporal lobe epilepsy, thereby providing a potential molecular mechanism for a new temporal lobe epilepsy diagnosis and treatment strategy.

Hypothalamic Orexinergic Neurons Projecting to the Mesencephalic Locomotor Region Are Activated by Voluntary Wheel Running Exercise in Rats

Background

Cardiovascular changes during exercise are regulated by a motor volitional signal, called central command, which originates in the rostral portions of the brain and simultaneously regulates somatomotor and autonomic nervous systems. Whereas we recently elucidated mesencephalic locomotor region (MLR) neurons projecting to the rostral ventrolateral medulla as a crucial component of the central circuit responsible for transmitting central command signals, upstream circuits that regulate the MLR neurons remain unknown. Orexinergic neurons, which primarily originate from the perifornical area (PeFA) of the hypothalamus and reportedly play roles in eliciting locomotion and elevating sympathetic activity, send axonal projection to the MLR. The knowledge led us to investigate whether central command signals are relayed through orexinergic neurons projecting to the MLR.

Methods

We performed anterograde transsynaptic tagging with AAV1 encoding Cre to confirm the presence of MLR neurons postsynaptic to the PeFA in rats. We also conducted retrograde neural tracing with retrograde AAV, combined with immunohistochemical staining, to examine the excitability of MLR-projecting orexinergic neurons in rats that were allowed to freely run on the wheel for 90 min.

Results

A significant number of MLR neurons were labeled with Cre, indicating that PeFA neurons make synaptic contacts with MLR neurons. Moreover, immunoreactivities of Fos, a marker of neuronal excitation, were found in many MLR-projecting orexinergic neurons by voluntary wheel running exercise, compared to non-exercising control rats, especially in the intermediate-posterior, rather than anterior, and medial, rather than lateral, portions within the orexinergic neuron-distributing domain.

Conclusion

The findings suggest that specifically located orexinergic neurons transmit central command signals onto the MLR for running exercise. Elucidating the role of these MLR-projecting orexinergic neurons in somatomotor control and autonomic cardiovascular control deserves further study to unveil central circuit mechanisms responsible for central command function.

Focused Ultrasound Stimulates the Prefrontal Cortex and Prevents MK-801-Induced Psychiatric Symptoms of Schizophrenia in Rats

BACKGROUND AND HYPOTHESIS

Treatment of schizophrenia remains a major challenge. Recent studies have focused on glutamatergic signaling hypoactivity through N-methyl-D-aspartate (NMDA) receptors. Low-intensity pulsed ultrasound (LIPUS) improves behavioral deficits and ameliorates neuropathology in dizocilpine (MK-801)-treated rats. The aim of this study was to investigate the efficacy of LIPUS against psychiatric symptoms and anxiety-like behaviors.

STUDY DESIGN

Rats assigned to 4 groups were pretreated with or without LIPUS for 5 days. The open field and prepulse inhibition tests were performed after saline or MK-801 (0.3 mg/kg) administration. Then, the neuroprotective effects of LIPUS on the MK-801-treated rats were evaluated using western blotting and immunohistochemical staining.

STUDY RESULTS

LIPUS stimulation of the prefrontal cortex (PFC) prevented deficits in locomotor activity and sensorimotor gating and improved anxiety-like behavior. MK-801 downregulated the expression of NR1, the NMDA receptor, in rat medial PFC (mPFC). NR1 expression was significantly higher in animals receiving LIPUS pretreatment compared to those receiving only MK-801. In contrast, a significant increase in c-Fos-positive cells in the mPFC and ventral tegmental area was observed in the MK-801-treated rats compared to those receiving only saline; this change was suppressed by pretreatment with LIPUS.

CONCLUSIONS

This study provides new evidence for the role of LIPUS stimulation in regulating the NMDA receptor and modulating c-Fos activity, which makes it a potentially valuable antipsychotic treatment for schizophrenia.

What Can Hippocampal Engrams Tell Us About Encoding Spatial Navigation?

The hippocampus is indispensable for episodic memories, but its particular role in the process is still unclear. This chapter briefly overviews past studies focusing on place cells and memory engrams, highlighting their potential roles in spatial navigation. Future work reconciling these two lines of studies would provide a comprehensive view of the specific contribution of the hippocampus and a better understanding of how memory engrams support memory.

Magnetoelectric Nanodiscs Enable Wireless Transgene-Free Neuromodulation

Deep-brain stimulation (DBS) with implanted electrodes revolutionized treatment of movement disorders and empowered neuroscience studies. Identifying less invasive alternatives to DBS may further extend its clinical and research applications. Nanomaterial-mediated transduction of magnetic fields into electric potentials offers an alternative to invasive DBS. Here, we synthesize magnetoelectric nanodiscs (MENDs) with a core-double shell Fe3O4-CoFe2O4-BaTiO3 architecture with efficient magnetoelectric coupling. We find robust responses to magnetic field stimulation in neurons decorated with MENDs at a density of 1 μg/mm2 despite individual-particle potentials below the neuronal excitation threshold. We propose a model for repetitive subthreshold depolarization, which combined with cable theory, corroborates our findings in vitro and informs magnetoelectric stimulation in vivo. MENDs injected into the ventral tegmental area of genetically intact mice at concentrations of 1 mg/mL enable remote control of reward behavior, setting the stage for mechanistic optimization of magnetoelectric neuromodulation and inspiring its future applications in fundamental and translational neuroscience.

Animal models of human insomnia

Insomnia disorder (chronic sleep continuity disturbance) is a debilitating condition affecting 5%-10% of the adult population worldwide. To date, researchers have attempted to model insomnia in animals through breeding strategies that create pathologically short-sleeping individuals or with drugs and environmental contexts that directly impose sleeplessness. While these approaches have been invaluable for identifying insomnia susceptibility genes and mapping the neural networks that underpin sleep-wake regulation, they fail to capture concurrently several of the core clinical diagnostic features of insomnia disorder in humans, where sleep continuity disturbance is self-perpetuating, occurs despite adequate sleep opportunity, and is often not accompanied by significant changes in sleep duration or architecture. In the present review, we discuss these issues and then outline ways animal models can be used to develop approaches that are more ecologically valid in their recapitulation of chronic insomnia's natural aetiology and pathophysiology. Conditioning of self-generated sleep loss with these methods promises to create a better understanding of the neuroadaptations that maintain insomnia, including potentially within the infralimbic cortex, a substrate at the crossroads of threat habituation and sleep.

In vivo labeling and quantitative imaging of neuronal populations using MRI

The study of neural circuits, which underlies perception, cognition, emotion, and behavior, is essential for understanding the mammalian brain, a complex organ consisting of billions of neurons. To study the structure and function of the brain, in vivo neuronal labeling and imaging techniques are crucial as they provide true physiological information that ex vivo methods cannot offer. In this paper, we present a new strategy for in vivo neuronal labeling and quantification using MRI. We demonstrate the efficacy of this method by delivering the oatp1a1 gene to the target neurons using rAAV2-retro virus. OATP1A1 protein expression on the neuronal membrane increased the uptake of a specific MRI contrast agent (Gd-EOB-DTPA), leading to hyperintense signals on T1W images of labeled neuronal populations. We also used dynamic contrast enhancement-based methods to obtain quantitative information on labeled neuronal populations in vivo.

UNRAVELing the synergistic effects of psilocybin and environment on brain-wide immediate early gene expression in mice

The effects of context on the subjective experience of serotonergic psychedelics have not been fully examined in human neuroimaging studies, partly due to limitations of the imaging environment. Here, we administered saline or psilocybin to mice in their home cage or an enriched environment, immunofluorescently-labeled brain-wide c-Fos, and imaged iDISCO+ cleared tissue with light sheet fluorescence microscopy (LSFM) to examine the impact of environmental context on psilocybin-elicited neural activity at cellular resolution. Voxel-wise analysis of c-Fos-immunofluorescence revealed clusters of neural activity associated with main effects of context and psilocybin-treatment, which were validated with c-Fos+ cell density measurements. Psilocybin increased c-Fos expression in subregions of the neocortex, caudoputamen, central amygdala, and parasubthalamic nucleus while it decreased c-Fos in the hypothalamus, cortical amygdala, striatum, and pallidum in a predominantly context-independent manner. To gauge feasibility of future mechanistic studies on ensembles activated by psilocybin, we confirmed activity- and Cre-dependent genetic labeling in a subset of these neurons using TRAP2+/-;Ai14+ mice. Network analyses treating each psilocybin-sensitive cluster as a node indicated that psilocybin disrupted co-activity between highly correlated regions, reduced brain modularity, and dramatically attenuated intermodular co-activity. Overall, our results indicate that main effects of context and psilocybin were robust, widespread, and reorganized network architecture, whereas context×psilocybin interactions were surprisingly sparse.

Activity-induced gene expression in the human brain

Activity-induced gene expression underlies synaptic plasticity and brain function. Here, using molecular sequencing techniques, we define activity-dependent transcriptomic and epigenomic changes at the tissue and single-cell level in the human brain following direct electrical stimulation of the anterior temporal lobe in patients undergoing neurosurgery. Genes related to transcriptional regulation and microglia-specific cytokine activity displayed the greatest induction pattern, revealing a precise molecular signature of neuronal activation in the human brain.

Chemogenetic Activation of Oxytocin Neurons Improves Pain in a Reserpine-induced Fibromyalgia Rat Model

Fibromyalgia (FM) is a syndrome characterized by chronic pain with depression as a frequent comorbidity. However, efficient management of the pain and depressive symptoms of FM is lacking. Given that endogenous oxytocin (OXT) contributes to the regulation of pain and depressive disorders, herein, we investigated the role of OXT in an experimental reserpine-induced FM model. In FM model, OXT-monomeric red fluorescent protein 1 (OXT-mRFP1) transgenic rats exhibited increased depressive behavior and sensitivity in a mechanical nociceptive test, suggesting reduced pain tolerance. Additionally, the development of the FM-like phenotype in OXT-mRFP1 FM model rats was accompanied by a significant reduction in OXT mRNA expression in the magnocellular neurons of the paraventricular nucleus. OXT-mRFP1 FM model rats also had significantly fewer tryptophan hydroxylase (TPH)- and tyrosine hydroxylase (TH)-immunoreactive (ir) neurons as well as reduced serotonin and norepinephrine levels in the dorsal raphe and locus coeruleus. To investigate the effects of stimulating the endogenous OXT pathway, rats expressing OXT-human muscarinic acetylcholine receptor (hM3Dq)-mCherry designer receptors exclusively activated by designer drugs (DREADDs) were also assessed in the FM model. Treatment of these rats with clozapine-N-oxide (CNO), an hM3Dq-activating drug, significantly improved characteristic FM model-induced pathophysiological pain, but did not alter depressive-like behavior. The chemogenetically induced effects were reversed by pre-treatment with an OXT receptor antagonist, confirming the specificity of action via the OXT pathway. These results indicate that endogenous OXT may have analgesic effects in FM, and could be a potential target for effective pain management strategies for this disorder.

Training-induced circuit-specific excitatory synaptogenesis in mice is required for effort control

Synaptogenesis is essential for circuit development; however, it is unknown whether it is critical for the establishment and performance of goal-directed voluntary behaviors. Here, we show that operant conditioning via lever-press for food reward training in mice induces excitatory synapse formation onto a subset of anterior cingulate cortex neurons projecting to the dorsomedial striatum (ACC→DMS). Training-induced synaptogenesis is controlled by the Gabapentin/Thrombospondin receptor α2δ-1, which is an essential neuronal protein for proper intracortical excitatory synaptogenesis. Using germline and conditional knockout mice, we found that deletion of α2δ-1 in the adult ACC→DMS circuit diminishes training-induced excitatory synaptogenesis. Surprisingly, this manipulation does not impact learning but results in a significant increase in effort exertion without affecting sensitivity to reward value or changing contingencies. Bidirectional optogenetic manipulation of ACC→DMS neurons rescues or phenocopies the behaviors of the α2δ-1 cKO mice, highlighting the importance of synaptogenesis within this cortico-striatal circuit in regulating effort exertion.

Sustaining wakefulness: Brainstem connectivity in human consciousness

Consciousness is comprised of arousal (i.e., wakefulness) and awareness. Substantial progress has been made in mapping the cortical networks that modulate awareness in the human brain, but knowledge about the subcortical networks that sustain arousal is lacking. We integrated data from ex vivo diffusion MRI, immunohistochemistry, and in vivo 7 Tesla functional MRI to map the connectivity of a subcortical arousal network that we postulate sustains wakefulness in the resting, conscious human brain, analogous to the cortical default mode network (DMN) that is believed to sustain self-awareness. We identified nodes of the proposed default ascending arousal network (dAAN) in the brainstem, hypothalamus, thalamus, and basal forebrain by correlating ex vivo diffusion MRI with immunohistochemistry in three human brain specimens from neurologically normal individuals scanned at 600-750 μm resolution. We performed deterministic and probabilistic tractography analyses of the diffusion MRI data to map dAAN intra-network connections and dAAN-DMN internetwork connections. Using a newly developed network-based autopsy of the human brain that integrates ex vivo MRI and histopathology, we identified projection, association, and commissural pathways linking dAAN nodes with one another and with cortical DMN nodes, providing a structural architecture for the integration of arousal and awareness in human consciousness. We release the ex vivo diffusion MRI data, corresponding immunohistochemistry data, network-based autopsy methods, and a new brainstem dAAN atlas to support efforts to map the connectivity of human consciousness.

Dim artificial light at night alters immediate early gene expression throughout the avian brain

Artificial light at night (ALAN) is a pervasive pollutant that alters physiology and behavior. However, the underlying mechanisms triggering these alterations are unknown, as previous work shows that dim levels of ALAN may have a masking effect, bypassing the central clock. Light stimulates neuronal activity in numerous brain regions which could in turn activate downstream effectors regulating physiological response. In the present study, taking advantage of immediate early gene (IEG) expression as a proxy for neuronal activity, we determined the brain regions activated in response to ALAN. We exposed zebra finches to dim ALAN (1.5 lux) and analyzed 24 regions throughout the brain. We found that the overall expression of two different IEGs, cFos and ZENK, in birds exposed to ALAN were significantly different from birds inactive at night. Additionally, we found that ALAN-exposed birds had significantly different IEG expression from birds inactive at night and active during the day in several brain areas associated with vision, movement, learning and memory, pain processing, and hormone regulation. These results give insight into the mechanistic pathways responding to ALAN that underlie downstream, well-documented behavioral and physiological changes.

Molecular and cellular mechanisms of the first social relationship: A conserved role of 5-HT from mice to monkeys, upstream of oxytocin

Maternal affiliation by infants is the first social behavior of mammalian animals. We report here that elimination of the Tph2 gene essential for serotonin synthesis in the brain reduced affiliation in mice, rats, and monkeys. Calcium imaging and c-fos immunostaining showed maternal odors activation of serotonergic neurons in the raphe nuclei (RNs) and oxytocinergic neurons in the paraventricular nucleus (PVN). Genetic elimination of oxytocin (OXT) or its receptor reduced maternal preference. OXT rescued maternal preference in mouse and monkey infants lacking serotonin. Tph2 elimination from RN serotonergic neurons innervating PVN reduced maternal preference. Reduced maternal preference after inhibiting serotonergic neurons was rescued by oxytocinergic neuronal activation. Our genetic studies reveal a role for serotonin in affiliation conserved from mice and rats to monkeys, while electrophysiological, pharmacological, chemogenetic, and optogenetic studies uncover OXT downstream of serotonin. We suggest serotonin as the master regulator upstream of neuropeptides in mammalian social behaviors.

Immortal orexin cell transplants restore motor-arousal synchrony during cataplexy

Waking behaviors such as sitting or standing require suitable levels of muscle tone. But it is unclear how arousal and motor circuits communicate with one another so that appropriate motor tone occurs during wakefulness. Cataplexy is a peculiar condition in which muscle tone is involuntarily lost during normal periods of wakefulness. Cataplexy therefore provides a unique opportunity for identifying the signaling mechanisms that synchronize motor and arousal behaviors. Cataplexy occurs when hypothalamic orexin neurons are lost in narcolepsy; however, it is unclear if motor-arousal decoupling in cataplexy is directly or indirectly caused by orexin cell loss. Here, we used genomic, proteomic, chemogenetic, electrophysiological, and behavioral assays to determine if grafting orexin cells into the brain of cataplectic (i.e., orexin^-/-) mice restores normal motor-arousal behaviors by preventing cataplexy. First, we engineered immortalized orexin cells and found that they not only produce and release orexin but also exhibit a gene profile that mimics native orexin neurons. Second, we show that engineered orexin cells thrive and integrate into host tissue when transplanted into the brain of mice. Next, we found that grafting only 200-300 orexin cells into the dorsal raphe nucleus-a region densely innervated by native orexin neurons-reduces cataplexy. Last, we show that real-time chemogenetic activation of orexin cells restores motor-arousal synchrony by preventing cataplexy. We suggest that orexin signaling is critical for arousal-motor synchrony during wakefulness and that the dorsal raphe plays a pivotal role in coupling arousal and motor behaviors.

The neural pathway of the hyperthermic response to antagonists of the transient receptor potential vanilloid-1 channel

We identified the neural pathway of the hyperthermic response to TRPV1 antagonists. We showed that hyperthermia induced by i.v. AMG0347, AMG 517, or AMG8163 did not occur in rats with abdominal sensory nerves desensitized by pretreatment with a low i.p. dose of resiniferatoxin (RTX, TRPV1 agonist). However, neither bilateral vagotomy nor bilateral transection of the greater splanchnic nerve attenuated AMG0347-induced hyperthermia. Yet, this hyperthermia was attenuated by bilateral high cervical transection of the spinal dorsolateral funiculus (DLF). To explain the extra-splanchnic, spinal mediation of TRPV1 antagonist-induced hyperthermia, we proposed that abdominal signals that drive this hyperthermia originate in skeletal muscles - not viscera. If so, in order to prevent TRPV1 antagonist-induced hyperthermia, the desensitization caused by i.p. RTX should spread into the abdominal-wall muscles. Indeed, we found that the local hypoperfusion response to capsaicin (TRPV1 agonist) in the abdominal-wall muscles was absent in i.p. RTX-desensitized rats. We then showed that the most upstream (lateral parabrachial, LPB) and the most downstream (rostral raphe pallidus) nuclei of the intrabrain pathway that controls autonomic cold defenses are also required for the hyperthermic response to i.v. AMG0347. Injection of muscimol (inhibitor of neuronal activity) into the LPB or injection of glycine (inhibitory neurotransmitter) into the raphe blocked the hyperthermic response to i.v. AMG0347, whereas i.v. AMG0347 increased the number of c-Fos cells in the raphe. We conclude that the neural pathway of TRPV1 antagonist-induced hyperthermia involves TRPV1-expressing sensory nerves in trunk muscles, the DLF, and the same LPB-raphe pathway that controls autonomic cold defenses.

Perfluorononanoic Acid Induces Neurotoxicity via Synaptogenesis Signaling in Zebrafish

Perfluorononanoic acid (PFNA), commonly used as an alternative polyfluorinated compound (PFC) of perfluorooctanoic acid (PFOA), has been widely detected in the aquatic environment. Previous ecotoxicological and epidemiological results suggested that some neurobehavioral effects were associated with PFC exposure; however, the ecological impacts and underlying neurotoxicity mechanisms remain unclear, particularly in aquatic organisms during sensitive, early developmental stages. In this study, zebrafish embryos were exposed to environmentally relevant concentrations of PFNA for 120 h, and the neurological effects of PFNA were comprehensively assessed using transcriptional, biochemical, morphological, and behavioral assays. RNA sequencing and advanced bioinformatics analyses predicted and characterized the key biological processes and pathways affected by PFNA exposure, which included the synaptogenesis signaling pathway, neurotransmitter synapse, and CREB signaling in neurons. Neurotransmitter levels (acetylcholine, glutamate, 5-hydroxytryptamine, γ-aminobutyric acid, dopamine, and noradrenaline) were significantly decreased in zebrafish larvae, and the Tg(gad67:GFP) transgenic line revealed a decreased number of GABAergic neurons in PFNA-treated larvae. Moreover, the swimming distance, rotation frequency, and activity degree were also significantly affected by PFNA, linking molecular-level changes to behavioral consequences.

An Optrode Array for Spatiotemporally Precise Large-Scale Optogenetic Stimulation of Deep Cortical Layers in Non-human Primates

Optogenetics has transformed studies of neural circuit function, but remains challenging to apply in non-human primates (NHPs). A major challenge is delivering intense and spatially precise patterned photostimulation across large volumes in deep tissue. Here, we have developed and validated the Utah Optrode Array (UOA) to meet this critical need. The UOA is a 10×10 glass waveguide array bonded to an electrically-addressable μLED array. In vivo electrophysiology and immediate early gene (c-fos) immunohistochemistry demonstrated the UOA allows for large-scale spatiotemporally precise neuromodulation of deep tissue in macaque primary visual cortex. Specifically, the UOA permits both focal (single layers or columns), and large-scale (across multiple layers or columns) photostimulation of deep cortical layers, simply by varying the number of simultaneously activated μLEDs and/or the light irradiance. These results establish the UOA as a powerful tool for studying targeted neural populations within single or across multiple deep layers in complex NHP circuits.

UNRAVELing the synergistic effects of psilocybin and environment on brain-wide immediate early gene expression in mice

The effects of context on the subjective experience of serotonergic psychedelics have not been fully examined in human neuroimaging studies, partly due to limitations of the imaging environment. Here, we administered saline or psilocybin to mice in their home cage or an enriched environment, immunofluorescently-labeled brain-wide c-Fos, and imaged cleared tissue with light sheet microscopy to examine the impact of context on psilocybin-elicited neural activity at cellular resolution. Voxel-wise analysis of c-Fos-immunofluorescence revealed differential neural activity, which we validated with c-Fos + cell density measurements. Psilocybin increased c-Fos expression in the neocortex, caudoputamen, central amygdala, and parasubthalamic nucleus and decreased c-Fos in the hypothalamus, cortical amygdala, striatum, and pallidum. Main effects of context and psilocybin-treatment were robust, widespread, and spatially distinct, whereas interactions were surprisingly sparse.

The Pedunculopontine Tegmental Nucleus is not Important for Breathing Impairments Observed in a Parkinson's Disease Model

Parkinson's disease (PD) is a motor disorder resulting from degeneration of dopaminergic neurons of substantia nigra pars compacta (SNpc), with classical and non-classical symptoms such as respiratory instability. An important region for breathing control, the Pedunculopontine Tegmental Nucleus (PPTg), is composed of cholinergic, glutamatergic, and GABAergic neurons. We hypothesize that degenerated PPTg neurons in a PD model contribute to the blunted respiratory activity. Adult mice (40 males and 29 females) that express the fluorescent green protein in cholinergic, glutamatergic or GABAergic cells were used (Chat-cre Ai6, Vglut₂-cre Ai6 and Vgat-cre Ai6) and received bilateral intrastriatal injections of vehicle or 6-hydroxydopamine (6-OHDA). Ten days later, the animals were exposed to hypercapnia or hypoxia to activate PPTg neurons. Vglut₂-cre Ai6 animals also received retrograde tracer injections (cholera toxin b) into the retrotrapezoid nucleus (RTN) or preBötzinger Complex (preBötC) and anterograde tracer injections (AAV-mCherry) into the SNpc. In 6-OHDA-injected mice, there is a 77% reduction in the number of dopaminergic neurons in SNpc without changing the number of neurons in the PPTg. Hypercapnia activated fewer Vglut₂ neurons in PD, and hypoxia did not activate PPTg neurons. PPTg neurons do not input RTN or preBötC regions but receive projections from SNpc. Although our results did not show a reduction in the number of glutamatergic neurons in PPTg, we observed a reduction in the number of neurons activated by hypercapnia in the PD animal model, suggesting that PPTg may participate in the hypercapnia ventilatory response.

Large-scale brain correlates of sweet versus cocaine reward in rats

Cocaine induces many supranormal changes in neuronal activity in the brain, notably in learning- and reward-related regions, in comparison with nondrug rewards-a difference that is thought to contribute to its relatively high addictive potential. However, when facing a choice between cocaine and a nondrug reward (e.g., water sweetened with saccharin), most rats do not choose cocaine, as one would expect from the extent and magnitude of its global activation of the brain, but instead choose the nondrug option. We recently showed that cocaine, though larger in magnitude, is also an inherently more delayed reward than sweet water, thereby explaining why it has less value during choice and why rats opt for the more immediate nondrug option. Here, we used a large-scale Fos brain mapping approach to measure brain responses to each option in saccharin-preferring rats, with the hope to identify brain regions whose activity may explain the preference for the nondrug option. In total, Fos expression was measured in 142 brain levels corresponding to 52 brain subregions and composing 5 brain macrosystems. Overall, our findings confirm in rats with a preference for saccharin that cocaine induces more global brain activation than the preferred nondrug option does. Only very few brain regions were uniquely activated by saccharin. They included regions involved in taste processing (i.e., anterior gustatory cortex) and also regions involved in processing reward delay and intertemporal choice (i.e., some components of the septohippocampal system and its connections with the lateral habenula).

The Field-Dependent Nature of PageRank Values in Citation Networks

The value of scientific research can be easier to assess at the collective level than at the level of individual contributions. Several journal-level and article-level metrics aim to measure the importance of journals or individual manuscripts. However, many are citation-based and citation practices vary between fields. To account for these differences, scientists have devised normalization schemes to make metrics more comparable across fields. We use PageRank as an example metric and examine the extent to which field-specific citation norms drive estimated importance differences. In doing so, we recapitulate differences in journal and article PageRanks between fields. We also find that manuscripts shared between fields have different PageRanks depending on which field's citation network the metric is calculated in. We implement a degree-preserving graph shuffling algorithm to generate a null distribution of similar networks and find differences more likely attributed to field-specific preferences than citation norms. Our results suggest that while differences exist between fields' metric distributions, applying metrics in a field-aware manner rather than using normalized global metrics avoids losing important information about article preferences. They also imply that assigning a single importance value to a manuscript may not be a useful construct, as the importance of each manuscript varies by the reader's field.

Brown Slime Cap Mushroom (Chroogomphus rutilus, Agaricomycetes) Polysaccharide Resists Motion Sickness by Inhibiting the Activity of the Serotonin System in Mice

Motion sickness (MS) is a disorder of the autonomic nervous system caused by abnormal exercise with symptoms such as nausea, vomiting and drowsiness. More than 90% of the human population has experienced different degrees of MS. At present, anticholinergics, antihistamines, and sympathomimetic drugs are used for treating MS, but these drugs generally have some adverse reactions and are not suitable for all people. Therefore, it is necessary to develop anti-MS drugs that have high efficiency and no adverse effects. Previous studies have found that Chroogomphus rutilus polysaccharide (CRP) is effective at preventing and treating MS in rats and mice. However, its mechanism of action is not clear. To clarify whether the CRP has anti-MS effects in mice, and to clarify its mechanism, we performed behavioral, biochemical, and morphological tests in a Kunming mouse model. Our results indicate that CRPs can significantly relieve the symptoms of MS, and their effect is equivalent to that of scopolamine, a commonly used anti-MS medicine. Our results indicate that CRPs may directly act on the gastrointestinal chromaffin cells to inhibit the synthesis and release of serotonin (5-hydroxytryptamine, or 5-HT) and thus reduce the signal from the gastrointestinal tract.

Spontaneous neuronal regeneration in the forebrain of the leopard gecko (Eublepharis macularius) following neurochemical lesioning

BACKGROUND

Neurogenesis is the ability to generate new neurons from resident stem/progenitor populations. Although often understood as a homeostatic process, several species of teleost fish, salamanders, and lacertid lizards are also capable of reactive neurogenesis, spontaneously replacing lost or damaged neurons. Here, we demonstrate that reactive neurogenesis also occurs in a distantly related lizard species, Eublepharis macularius, the leopard gecko.

RESULTS

To initiate reactive neurogenesis, the antimetabolite 3-acetylpyridine (3-AP) was administered. Four days following 3-AP administration there is a surge in neuronal cell death within a region of the forebrain known as the medial cortex (homolog of the mammalian hippocampal formation). Neuronal cell death is accompanied by a shift in resident microglial morphology and an increase neural stem/progenitor cell proliferation. By 30 days following 3-AP administration, the medial cortex was entirely repopulated by NeuN+ neurons. At the same time, local microglia have reverted to a resting state and cell proliferation by neural stem/progenitors has returned to levels comparable with uninjured controls.

CONCLUSIONS

Together, these data provide compelling evidence of reactive neurogenesis in leopard geckos, and indicate that the ability of lizards to spontaneously replace lost or damaged forebrain neurons is more taxonomically widespread and evolutionarily conserved than previously considered.

Abdominal surgery increases activity in several phoenixin immunoreactive nuclei

BACKGROUND

Research on the peptide phoenixin has increased in recent years and greatly widened the known scope of its functions since its discovery in 2013. Involvement of phoenixin has since been shown in anxiety, food intake, reproduction as well as emotional and immunological stress. To further evaluate its involvement in stress reactions, this study aims to investigate the effects of abdominal surgery, a well-established physical stressor, on the activity of phoenixin-immunoreactive brain nuclei.

METHODS

Male Sprague-Dawley rats (n = 6/group) were subjected to either an abdominal surgery stress protocol or a sham operation. Animals in the verum group were anesthetized, the abdominal cavity opened and the cecum palpated, followed by closing of the abdomen and recovery. Sham operated animals only received inhalation anesthesia and time for recovery. All animals were subsequently sacrificed and brains processed and evaluated for c-Fos activity as well as phoenixin density.

RESULTS

Compared to control, abdominal surgery significantly increased c-Fos activity in the paraventricular nucleus (PVN, 6.4-fold, p < 0.001), the medial part of the nucleus of the solitary tract (mNTS, 3.8-fold, p < 0.001), raphe pallidus (RPa, 3.6-fold, p < 0.001), supraoptic nucleus (SON, 3.2-fold, p < 0.001), ventrolateral medulla (VLM, also called A1C1, 3.0-fold, p < 0.001), dorsal motor nucleus of vagus (DMN, 2.9-fold, p < 0.001), locus coeruleus (LC, 1.8-fold, p < 0.01) and Edinger-Westphal nucleus (EW, 1.6-fold, p < 0.05), while not significantly altering c-Fos activity in the amygdala (CeM, 1.3-fold, p > 0.05). Phoenixin immunoreactivity was not significantly affected by abdominal surgery (p > 0.05).

CONCLUSION

The observed abdominal surgery-related increase in activity in phoenixin immunoreactive nuclei compared to sham surgery controls supports the hypothesis of an involvement of phoenixin in stress reactions. Interestingly, various psychological and physical stressors lead to specific changes in activity and immunoreactivity in phoenixin-containing nuclei, giving rise to a stressor-specific involvement of phoenixin.

Network Neuroscience Untethered: Brain-Wide Immediate Early Gene Expression for the Analysis of Functional Connectivity in Freely Behaving Animals

Studying how spatially discrete neuroanatomical regions across the brain interact is critical to advancing our understanding of the brain. Traditional neuroimaging techniques have led to many important discoveries about the nature of these interactions, termed functional connectivity. However, in animal models these traditional neuroimaging techniques have generally been limited to anesthetized or head-fixed setups or examination of small subsets of neuroanatomical regions. Using the brain-wide expression density of immediate early genes (IEG), we can assess brain-wide functional connectivity underlying a wide variety of behavioural tasks in freely behaving animal models. Here, we provide an overview of the necessary steps required to perform IEG-based analyses of functional connectivity. We also outline important considerations when designing such experiments and demonstrate the implications of these considerations using an IEG-based network dataset generated for the purpose of this review.

Deep brain stimulation of the anterior nuclei of the thalamus can alleviate seizure severity and induce hippocampal GABAergic neuronal changes in a pilocarpine-induced epileptic mouse brain

Deep brain stimulation (DBS) of the anterior nucleus of the thalamus (ANT) has been widely used as an effective treatment for refractory temporal lobe epilepsy. Despite its promising clinical outcome, the exact mechanism of how ANT-DBS alleviates seizure severity has not been fully understood, especially at the cellular level. To assess effects of DBS, the present study examined electroencephalography (EEG) signals and locomotor behavior changes and conducted immunohistochemical analyses to examine changes in neuronal activity, number of neurons, and neurogenesis of inhibitory neurons in different hippocampal subregions. ANT-DBS alleviated seizure activity, abnormal locomotor behaviors, reduced theta-band, increased gamma-band EEG power in the interictal state, and increased the number of neurons in the dentate gyrus (DG). The number of parvalbumin- and somatostatin-expressing inhibitory neurons was recovered to the level in DG and CA1 of naïve mice. Notably, BrdU-positive inhibitory neurons were increased. In conclusion, ANT-DBS not only could reduce the number of seizures, but also could induce neuronal changes in the hippocampus, which is a key region involved in chronic epileptogenesis. Importantly, our results suggest that ANT-DBS may lead to hippocampal subregion-specific cellular recovery of GABAergic inhibitory neurons.

Amplification of olfactory signals by Anoctamin 9 is important for mammalian olfaction

Sensing smells of foods, prey, or predators determines animal survival. Olfactory sensory neurons in the olfactory epithelium (OE) detect odorants, where cAMP and Ca2+ play a significant role in transducing odorant inputs to electrical activity. Here we show Anoctamin 9, a cation channel activated by cAMP/PKA pathway, is expressed in the OE and amplifies olfactory signals. Ano9-deficient mice had reduced olfactory behavioral sensitivity, electro-olfactogram signals, and neural activity in the olfactory bulb. In line with the difference in olfaction between birds and other vertebrates, chick ANO9 failed to respond to odorants, whereas chick CNGA2, a major transduction channel, showed greater responses to cAMP. Thus, we concluded that the signal amplification by ANO9 is important for mammalian olfactory transduction.

Modulating cell signalling in vivo with magnetic nanotransducers

Weak magnetic fields offer nearly lossless transmission of signals within biological tissue. Magnetic nanomaterials are capable of transducing magnetic fields into a range of biologically relevant signals in vitro and in vivo. These nanotransducers have recently enabled magnetic control of cellular processes, from neuronal firing and gene expression to programmed apoptosis. Effective implementation of magnetically controlled cellular signalling relies on careful tailoring of magnetic nanotransducers and magnetic fields to the responses of the intended molecular targets. This primer discusses the versatility of magnetic modulation modalities and offers practical guidelines for selection of appropriate materials and field parameters, with a particular focus on applications in neuroscience. With recent developments in magnetic instrumentation and nanoparticle chemistries, including those that are commercially available, magnetic approaches promise to empower research aimed at connecting molecular and cellular signalling to physiology and behaviour in untethered moving subjects.

The effects of bilateral prostriata lesions on spatial learning and memory in the rat

Area prostriata is the primary limbic structure for rapid response to the visual stimuli in the far peripheral visual field. Recent studies have revealed that the prostriata receives inputs not only from the visual and auditory cortices but also from many structures critical for spatial processing and navigation. To gain insight into the functions of the prostriata in spatial learning and memory the present study examines the effects of bilateral lesions of the prostriata on motor ability, exploratory interest and spatial learning and memory using the open field, elevated plus-maze and Morris water maze tests. Our results show that the spatial learning and memory abilities of the rats with bilateral prostriata lesions are significantly reduced compared to the control and sham groups. In addition, the lesion rats are found to be less interested in space exploration and more anxious while the exercise capacity of the rats is not affected based on the first two behavioral tests. These findings suggest that the prostriata plays important roles in spatial learning and memory and may be involved in anxiety as well.

CO2 exposure enhances Fos expression in hypothalamic neurons in rats during the light and dark phases of the diurnal cycle

Orexinergic (OX) neurons in the lateral hypothalamus (LH), perifornical area (PFA) and dorsomedial hypothalamus (DMH) play a role in the hypercapnic ventilatory response, presumably through direct inputs to central pattern generator sites and/or through interactions with other chemosensitive regions. OX neurons can produce and release orexins, excitatory neuropeptides involved in many functions, including physiological responses to changes in CO₂/pH. Thus, in the present study, we tested the hypothesis that different nuclei (LH, PFA and DMH) where the orexinergic neurons are located, show distinct activation by CO₂ during the light-dark cycle phases. For this purpose, we evaluated the Fos and OXA expression by immunohistochemistry to identify neurons that co-localize Fos + OXA in the LH, LPeF, MPeF and DMH in the light-inactive and dark-active phase in Wistar rats subjected to 3 h of normocapnia or hypercapnia (7% CO₂). Quantitative analyses of immunoreactive neurons show that hypercapnia caused an increase in the number of neurons expressing Fos in the LH, LPeF, MPeF and DMH in the light and dark phases. In addition, the number of Fos + OXA neurons increased in the LPeF and DMH independently of the phases of the diurnal cycle; whereas in the MPeF, this increase was observed exclusively in the light phase. Thus, we suggest that OX neurons are selectively activated by hypercapnia throughout the diurnal cycle, reinforcing the differential role of nuclei in the hypothalamus during central chemosensitivity.

Impaired Morris water task retention following T21 light dark cycle exposure is not due to reduced hippocampal c-FOS expression

Circadian rhythms influence virtually all aspects of physiology and behavior. This is problematic when circadian rhythms no longer reliably predict time. Circadian rhythm disruption can impair memory, yet we don’t know how this fully works at the systems and molecular level. When trying to determine the root of a memory impairment, assessing neuronal activation with c-FOS is useful. This has yet to be assessed in the hippocampi of circadian rhythm disrupted rats in a hippocampal gold standard task. Rats were trained on the Morris water task (MWT), then received 6 days of a 21-h day (T21), 13 days of a normal light dark cycle, probe trial, and tissue extraction an hour later. Despite having impaired memory in the probe trial, compared to controls there were no differences in c-FOS expression in hippocampal sub regions: CA1; CA3; Dentate gyrus. These data confirm others in hamsters demonstrating that arrhythmicity which produces an impairment in spontaneous alternation does not affect c-FOS in the dentate gyrus. The current study indicates that the memory impairment induced by a lighting manipulation is likely not due to attenuated neuronal activation. Determining how the master clock in the brain communicates with the hippocampus is needed to untangle the relationship between circadian rhythms and memory.

A red nucleus-VTA glutamate pathway underlies exercise reward and the therapeutic effect of exercise on cocaine use

Physical exercise is rewarding and protective against drug abuse and addiction. However, the neural mechanisms underlying these actions remain unclear. Here, we report that long-term wheel-running produced a more robust increase in c-fos expression in the red nucleus (RN) than in other brain regions. Anatomic and functional assays demonstrated that most RN magnocellular portion (RNm) neurons are glutamatergic. Wheel-running activates a subset of RNm glutamate neurons that project to ventral tegmental area (VTA) dopamine neurons. Optogenetic stimulation of this pathway was rewarding, as assessed by intracranial self-stimulation and conditioned place preference, whereas optical inhibition blocked wheel-running behavior. Running wheel access decreased cocaine self-administration and cocaine seeking during extinction. Last, optogenetic stimulation of the RNm-to-VTA glutamate pathway inhibited responding to cocaine. Together, these findings indicate that physical exercise activates a specific RNm-to-VTA glutamatergic pathway, producing exercise reward and reducing cocaine intake.

To investigate the internal association between SARS-CoV-2 infections and cancer through bioinformatics

Severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2), also known as COVID-19, is currently prevalent worldwide and poses a significant threat to human health. Individuals with cancer may have an elevated risk for SARS-CoV-2 infections and adverse outcomes. Therefore, it is necessary to explore the internal relationship between these two diseases. In this study, transcriptome analyses were performed to detect mutual pathways and molecular biomarkers in three types of common cancers of the breast, liver, colon, and COVID-19. Such analyses could offer a valuable understanding of the association between COVID-19 and cancer patients. In an analysis of RNA sequencing datasets for three types of cancers and COVID-19, we identified a sum of 38 common differentially expressed genes (DEGs). A variety of combinational statistical approaches and bioinformatics techniques were utilized to generate the protein-protein interaction (PPI) network. Subsequently, hub genes and critical modules were found using this network. In addition, a functional analysis was conducted using ontologies keywords, and pathway analysis was also performed. Some common associations between cancer and the risk and prognosis of COVID-19 were discovered. The datasets also revealed transcriptional factors-gene interplay, protein-drug interaction, and a DEGs-miRNAs coregulatory network with common DEGs. The potential medications discovered in this investigation could be useful in treating cancer and COVID-19.

Social Fear Affects Limbic System Neuronal Activity and Gene Expression

Social anxiety disorder (SAD) is a highly prevalent and comorbid anxiety disorder with rather unclear underlying mechanisms. Here, we aimed to characterize neurobiological changes occurring in mice expressing symptoms of social fear and to identify possible therapeutic targets for SAD. Social fear was induced via social fear conditioning (SFC), a validated animal model of SAD. We assessed the expression levels of the immediate early genes (IEGs) cFos, Fosl2 and Arc as markers of neuronal activity and the expression levels of several genes of the GABAergic, serotoninergic, oxytocinergic, vasopressinergic and neuropeptide Y (NPY)-ergic systems in brain regions involved in social behavior or fear-related behavior in SFC+ and SFC− mice 2 h after exposure to a conspecific. SFC+ mice showed a decreased number and density of cFos-positive cells and decreased expression levels of IEGs in the dorsal hippocampus. SFC+ mice also showed alterations in the expression of NPY and serotonin system-related genes in the paraventricular nucleus of the hypothalamus, basolateral amygdala, septum and dorsal raphe nucleus, but not in the dorsal hippocampus. Our results describe neuronal alterations occurring during the expression of social fear and identify the NPY and serotonergic systems as possible targets in the treatment of SAD.

A spatiotemporal increase of neuronal activity accompanies the motivational effect of wheel running in mice

Spatiotemporal patterns of neuronal activity underlying the motivational effect of rotating running wheels (RWs) in rodents remain largely undetermined. Here, we investigated changes of neuronal activity among brain regions associated with motivation across different intensities of motivation for RWs in mice. Daily exposure to RWs gradually increased rotation number, then became stable after approximately 3 weeks. Immunohistochemical analyses revealed that the number of c-Fos (a neuronal activity marker)-positive cells increased in the medial prefrontal cortex (mPFC), core and shell of the nucleus accumbens (NAc), dorsal striatum (Str), and lateral septum (LS) at day 1, day 9, and days 20-24, in a time-dependent manner. Additionally, despite exposure to locked RWs for over 7 days after establishing stable rotation with 3-week RW access, increased c-Fos expression was still observed in most of these brain areas. Furthermore, daily overnight RW access developed stable rotation by day 6, with high and low rotation numbers at the start and end of the overnight session, respectively. The number of c-Fos-positive cells at the start of RW rotation was significantly higher than at the end of RW rotation in most brain regions. Furthermore, after establishing stable rotation, the number of c-Fos-positive cells increased in the mPFC and shell of the NAc of mice that only observed RWs. These findings suggest that the subareas of the mPFC and NAc may be critically involved in the motivational effects of RW rotations.

Effects of high-frequency near infrared laser irradiation on experimental tooth movement-induced pain in rats

Discomfort and dull pain are known side effects of orthodontic treatment. Pain is expected to be reduced by near-infrared (NIR) lasers; however, the mechanism underlying effects of short-pulse NIR lasers in the oral and maxillofacial area remains unclear. This study aimed to examine the effects of high-frequency NIR diode laser irradiation on pain during experimental tooth movement (ETM) on 120 J. NIR laser with 910 nm wavelength, 45 W maximum output power, 300 mW average output power, and 200 ns pulse width (Lumix 2; (Lumix 2; Fisioline, Verduno CN, Italy) was used for the experiment. A nickel-titanium-closed coil was used to apply a 50-gf force between the maxillary left-side first molar and incisor in 7-week-old Sprague-Dawley rats (280-300 g) to induce ETM. We measured facial-grooming frequency and vacuous chewing movement (VCM) period between laser-irradiation and ETM groups. We performed immunofluorescent histochemistry analysis to quantify levels of Iba-1, astrocytes, and c-fos protein-like immunoreactivity (Fos-IR) in the trigeminal spinal nucleus caudalis (Vc). Compared with the ETM group, the laser irradiation group had significantly decreased facial-grooming frequency (P = 0.0036), VCM period (P = 0.043), Fos-IR (P = 0.0028), Iba-1 levels (P = 0.0069), and glial fibrillary acidic protein (GFAP) levels (P = 0.0071). High-frequency NIR diode laser irradiation appears to have significant analgesic effects on ETM-induced pain, which involve inhibiting neuronal activity, microglia, and astrocytes, and it inhibits c-fos, Iba-1, and GFAP expression, reducing ETM-induced pain in rats. High-frequency NIR diode laser application could be applied to reduce pain during orthodontic tooth movement.

What does engram encode?: Heterogeneous memory engrams for different aspects of experience

Long-lasting synaptic changes within the neuronal network mediate memory. Neurons bearing such physical traces of memory (memory engram cells) are often equated with neurons expressing immediate early genes (IEGs) during a specific experience. However, past studies observed the expression of different IEGs in non-overlapping neurons or synaptic plasticity in neurons that do not express a particular IEG. Importantly, recent studies revealed that distinct subsets of neurons expressing different IEGs or even IEG negative-(yet active) neurons support different aspects of memory or computation, suggesting a more complex nature of memory engram cells than previously thought. In this short review, we introduce studies revealing such heterogeneous composition of the memory engram and discuss how the memory system benefits from it.

The physiological control of eating: signals, neurons, and networks

During the past 30 yr, investigating the physiology of eating behaviors has generated a truly vast literature. This is fueled in part by a dramatic increase in obesity and its comorbidities that has coincided with an ever increasing sophistication of genetically based manipulations. These techniques have produced results with a remarkable degree of cell specificity, particularly at the cell signaling level, and have played a lead role in advancing the field. However, putting these findings into a brain-wide context that connects physiological signals and neurons to behavior and somatic physiology requires a thorough consideration of neuronal connections: a field that has also seen an extraordinary technological revolution. Our goal is to present a comprehensive and balanced assessment of how physiological signals associated with energy homeostasis interact at many brain levels to control eating behaviors. A major theme is that these signals engage sets of interacting neural networks throughout the brain that are defined by specific neural connections. We begin by discussing some fundamental concepts, including ones that still engender vigorous debate, that provide the necessary frameworks for understanding how the brain controls meal initiation and termination. These include key word definitions, ATP availability as the pivotal regulated variable in energy homeostasis, neuropeptide signaling, homeostatic and hedonic eating, and meal structure. Within this context, we discuss network models of how key regions in the endbrain (or telencephalon), hypothalamus, hindbrain, medulla, vagus nerve, and spinal cord work together with the gastrointestinal tract to enable the complex motor events that permit animals to eat in diverse situations.

Fos response of the tail of the ventral tegmental area to food restriction entails a prediction error processing

The tail of the ventral tegmental area (tVTA) or rostromedial tegmental nucleus (RMTg) receives lateral habenula inputs and projects heavily to midbrain dopamine neurons. Midbrain dopamine and lateral habenula neurons participate in learning processes predicting the outcomes of actions, placing the tVTA in a critical location into prediction error pathways. tVTA GABA neurons show electrophysiological inhibition or activation after reward and aversive stimuli, respectively, and their predictive cues. tVTA molecular recruitment, however, is not elicited by all aversive stimuli. Indeed, precipitated opioid withdrawal, repeated footshocks or food restriction raise tVTA Fos expression, whereas various other unpleasant, stressful or painful stimuli does not elicit that molecular response. However, the basis of that difference remains unknown. In the present study, we tried to disentangle whether the tVTA c-Fos induction observed after food restriction was due to the aversive state of food restriction or to procedure-related reward prediction error. To this end, male Sprague-Dawley rats were food-restricted for 7-8 days. During this period, animals were handled and weighed every day before feeding. On the test day, rats underwent several behavioral procedures to explore the impact of food restriction and food-predictive cue exposure on tVTA c-Fos expression. We showed that food restriction per se was not able to recruit c-Fos in the tVTA. On the contrary, the food-predicting cues induced c-Fos locally in the absence of feeding, whereas the food-predicting cues followed by feeding evoked lower c-Fos expression. Overall, our results support the proposed involvement of the tVTA in reward prediction error.