Functional neuroanatomy of the central noradrenergic system

VNS paired with training enhances recognition memory: mechanistic insights from proteomic analysis of the hippocampal synapse

Introduction

Recognition memory, an essential component of cognitive health, can suffer from biological limitations of stress, aging, or neurodegenerative disease. Vagus nerve stimulation (VNS) is a neuromodulation therapy with the potential to improve cognitive function. This study investigated the effectiveness of multiple sessions of VNS to enhance recognition memory in healthy rodents and the underlying cognitive benefits of VNS by proteomic analysis of the synaptosome.

Methods

Rats demonstrated VNS-induced recognition memory improvements using a novel object recognition (NOR) task. Using the LC-MS/MS method, roughly 3,000 proteins in the synaptosome of the hippocampus were analyzed.

Results

Protein-protein interaction (PPI) enrichment analysis found differentially expressed proteins related to synaptic signaling and neurotransmitter pathways. PPI network analysis identified six unique protein clusters, including a cluster of synaptic signaling related pathways. Using ingenuity pathway analysis (IPA), rapamycin-insensitive companion of mTOR was identified as an upstream regulator of synaptosome changes due to VNS-paired training.

Discussion

Based on these results, it is proposed that VNS may mediate cognitive enhancement via increases in glutamatergic signaling and early LTP during the consolidation period, followed by sustained synaptic plasticity via modified post-synaptic receptor expression and dendritic outgrowth. Further investigation is required to determine if VNS is a good candidate to ameliorate cognitive impairment.

The effects of locus coeruleus ablation on mouse brain volume and microstructure evaluated by high-field MRI

The locus coeruleus (LC) produces most of the brain's noradrenaline (NA). Among its many roles, NA is often said to be neuroprotective and important for brain upkeep. For this reason, loss of LC integrity is thought to impact brain volume and microstructure as well as plasticity broadly. LC dysfunction is also a suspected driver in the development of neurodegenerative diseases. Nevertheless, the impact of LC dysfunction on the gross structure and microstructure of normal brains is not well-studied. We employed high-field ex vivo magnetic resonance imaging (MRI) to investigate brain volumetrics and microstructure in control (CON) mice and mice with LC ablation (LCA) at two ages, representing the developing brain and the fully matured brain. These whole-brain methods are known to be capable of detecting subtle morphological changes and brain microstructural remodeling. We found mice behavior consistent with histologically confirmed LC ablation. However, MRI showed no difference between CON and LCA groups with regard to brain size, relative regional volumes, or regional microstructural indices. Our findings suggest that LC-NA is not needed for postnatal brain maturation and growth in mice. Nor is it required for maintenance in the normal adult mouse brain, as no atrophy or microstructural aberration is detected after weeks of LC dysfunction. This adds clarity to the often-encountered notion that LC-NA is important for brain "trophic support" as it shows that such effects are likely most relevant to mechanisms related to brain plasticity and neuroprotection in the (pre)diseased brain.

Role of the locus coeruleus-noradrenergic system in stress-related psychopathology and resilience: Clinical and pre-clinical evidences

Stressful events, from daily stressors to traumatic experiences, are common and occur at any age. Despite the high prevalence of trauma, not everyone develops stress-related disorders like major depressive disorder (MDD) and post-traumatic stress disorder (PTSD), a variation attributed to resilience, the ability to adapt and avoid negative consequences of significant stress. This review examines the locus coeruleus-norepinephrine (LC-NE) system, a critical component in the brain's stress response. It discusses the LC-NE system's anatomical and functional complexity and its role in individual variability in stress responses. How different etiological factors and stress modalities affect the LC-NE system, influencing both adaptive stress responses and psychopathologies, are discussed and supported by evidence from human and animal studies. It also explores molecular and cellular adaptations in the LC that contribute to resilience, including roles of neuropeptide, inflammatory cytokines, and genetic modulation, and addresses developmental and sex differences in stress vulnerability. The need for a multifaceted approach to understand stress-induced psychopathologies is emphasized and pave the way for more personalized interventions for stress-related disorders.

Depression and metabolic connectivity: insights into the locus coeruleus, HF-rTMS, and anxiety

The use of repetitive Transcranial Magnetic Stimulation (rTMS) in treating major depressive disorder (MDD) is increasingly being explored in precision medicine. However, there's a notable lack of understanding of the underlying neurobiological effects, which limits our ability to correlate specific imaging features with treatment efficacy. As one possible neurobiological mechanism, clinical research has already shown that in MDD, lower norepinephrine release in the locus coeruleus (LC) triggers depressive symptoms, and pharmacological approaches that block norepinephrine reuptake boost its levels, easing depression. Surprisingly, the LC has not received a more pronounced focus in contemporary rTMS research. This study investigates the role of the LC in MDD and its response to high-frequency (HF)-rTMS using 18FDG-PET imaging. We compared LC metabolic connectivity between MDD patients (n = 43) and healthy controls (n = 32). Additionally, we evaluated the predictive value of LC connectivity for HF-rTMS treatment outcomes and examined post-treatment changes in LC metabolic connectivity. Our findings revealed significant differences in LC metabolic connectivity between MDD patients and controls. Baseline LC metabolic connectivity did not predict HF-rTMS treatment outcomes. However, post-treatment analyses showed a significant correlation between improved clinical outcomes and attenuation of LC metabolic connectivity in regions associated with cognitive control and the default mode network. Notably, a reduction in state anxiety moderated this relationship, highlighting the role of anxiety in HF-rTMS efficacy for MDD treatment. Our findings suggest that LC metabolic connectivity, influenced by state anxiety levels, may be crucial in HF-rTMS efficacy, offering further insights for personalized MDD treatment strategies.

Stereochemical optimization of N,2-substituted cycloalkylamines as norepinephrine reuptake inhibitors

The norepinephrine transporter (NET), encoded by the SLC6A2 gene, is one of three key monoamine neurotransmitter transporters. Inhibition of NET-mediated reuptake of norepinephrine by monoamine reuptake inhibitors has been the main therapeutic strategy to treat disorders such as depression, ADHD and Parkinson's disease. Nevertheless, lack of efficacy as well as risk of adverse effects are still common for these treatments underscoring the necessity to improve drug discovery efforts for this target. In this study, we developed new inhibitors based on 4-((2-(3,4-dichlorophenyl)cyclopentyl)amino)butan-1-ol (8), a potent NET inhibitor, which emerged from earlier virtual screening efforts using a predictive proteochemometric model. Hence, we optimized the N,2-substituted cycloalkylamine scaffold in three regions to design twenty new derivatives. To establish structure-activity relationships for these NET inhibitors, all novel compounds were tested utilizing an impedance-based 'transporter activity through receptor activation' assay. Moreover, all stereoisomers of the most potent compound (27) were synthesized and evaluated for their inhibitory potencies. Initial screening indicated that modifications in the cyclopentylamine moiety and phenyl substitutions decreased NET inhibition compared to 8, emphasizing the importance of the five-membered ring, secondary amine and dichloro-substitution pattern in NET binding. Substituting the original butylalcohol at the R 2 position with a rigid cyclohexanol yielded lead compound 27, with potency similar to reference inhibitor nisoxetine. Pharmacological characterization of all eight stereoisomers of 27 revealed varying inhibitory potencies, favoring a trans-orientation of the N,2-substituted cyclopentyl moiety. Molecular docking highlighted key interactions and the impact of a hydrophilic region in the binding pocket. This study presents a novel set of moderate to highly potent NET inhibitors, elucidating the influence of molecular orientation in the NET binding pocket and offering valuable insights into drug discovery efforts for monoamine transport-related treatments.

Cannabinoids and monoaminergic system: implications for learning and memory

Cannabinoids and the endocannabinoid system (ECS) have been intensively studied for their neuroregulatory roles in the central nervous system (CNS), especially in regulating learning and memory. However, many experimental and clinical studies obtained conflicting results indicating a complex network of interaction underlying the regulation of learning and memory by different cannabinoids and the ECS. The ECS influences neuronal synaptic communications, and therefore may exert different regulation via their different impact on other neurotransmitters. The monoaminergic system includes a variety of neurotransmitters, such as dopamine, norepinephrine, and serotonin, which play important roles in regulating mood, cognition, and reward. The interaction among cannabinoids, ECS and the monoaminergic system has drawn particular attention, especially their contributions to learning and memory. In this review, we summarized the current understanding of how cannabinoids, ECS and the monoaminergic system contribute to the process of learning and memory, and discussed the influences of monoaminergic neurotransmission by cannabinoids and ECS during this process.

Cardiac sympathetic denervation and anxiety in Parkinson disease

BACKGROUND

Anxiety in Parkinson disease (PD) negatively impacts quality of life. While research predominantly focuses on central nervous system changes, some evidence suggests a connection between peripheral autonomic dysfunctions and PD-related anxiety. The role of the peripheral autonomic nervous system in this context may be overlooked.

OBJECTIVES

This study explores the link between anxiety symptoms and cardiac sympathetic denervation in PD using 11C-meta-hydroxyephedrine ([11C]HED) PET cardiac imaging.

METHODS

We studied 34 non-demented PD subjects, assessing anxiety levels through the Spielberg Anxiety State-Trait test trait section (STAI-T). Patients underwent comprehensive assessments along with [11C]HED cardiac and [11C]DTBZ brain PET. To identify subdimensions of STAI-T, we employed principal components analysis (PCA). We examined associations between the anxiety subdimensions and two measures of cardiac sympathetic denervation from [11C]HED PET. We utilized correlation and linear regression models for these analyses.

RESULTS

PCA revealed two STAI-T results components: anxiety-depressive and pure anxiety subcomponents. Only pure anxiety significantly correlated with measures of cardiac sympathetic denervation (rhos -0.40, p = 0.018; 0.35, p = 0.043). Regression models confirmed a significant association, with cardiac sympathetic denervation explaining ∼20 % of pure anxiety variance, independent of sex, dopaminergic impairment, and anxiolytic treatments.

DISCUSSION

This study provides preliminary evidence of peripheral autonomic nervous system abnormalities contributing to PD-related anxiety, suggesting dysregulation in peripheral autonomic functions influencing anxiety perception.

Eyes on Memory: Pupillometry in Encoding and Retrieval

This review critically examines the contributions of pupillometry to memory research, primarily focusing on its enhancement of our understanding of memory encoding and retrieval mechanisms mainly investigated with the recognition memory paradigm. The evidence supports a close link between pupil response and memory formation, notably influenced by the type of novelty detected. This proposal reconciles inconsistencies in the literature regarding pupil response patterns that may predict successful memory formation, and highlights important implications for encoding mechanisms. The review also discusses the pupil old/new effect and its significance in the context of recollection and in reflecting brain signals related to familiarity or novelty detection. Additionally, the capacity of pupil response to serve as a true memory signal and to distinguish between true and false memories is evaluated. The evidence provides insights into the nature of false memories and offers a novel understanding of the cognitive mechanisms involved in memory distortions. When integrated with rigorous experimental design, pupillometry can significantly refine theoretical models of memory encoding and retrieval. Furthermore, combining pupillometry with neuroimaging and pharmacological interventions is identified as a promising direction for future research.

Temporal dynamics of autonomic nervous system responses under cognitive-emotional workload in obsessive-compulsive disorder

Dysregulation of the autonomic nervous system (ANS) is commonly observed in various mental disorders, particularly when individuals engage in prolonged cognitive-emotional tasks that require ANS adjustment to workload. Although the understanding of the temporal dynamics of sympathetic and parasympathetic tones in obsessive-compulsive disorder (OCD) is limited, analyzing ANS reactions to cognitive-emotional workload could provide valuable insights into one of the underlying causes of OCD. This study investigated the temporal dynamics of heart rate (HR) and pupil area (PA) while participants with OCD and healthy volunteers solved antisaccade tasks, with affective pictures serving as central fixation stimuli. The data of 31 individuals with OCD and 30 healthy volunteers were included in the study, comprising three separate blocks, each lasting approximately 8 min. The results revealed an increase in sympathetic tone in the OCD group, with the most noticeable rise occurring during the middle part of each block, particularly during the presentation of negative stimuli. Healthy volunteers demonstrated adaptive temporal dynamics of HR and PA from the first block to the last block of tasks, whereas individuals with OCD exhibited fewer changes over time, suggesting a reduced adaptation of the ANS sympathetic tone to cognitive-emotional workload in OCD.

Functionality of arousal-regulating brain circuitry at rest predicts human cognitive abilities

Arousal state is regulated by subcortical neuromodulatory nuclei, such as locus coeruleus, which send wide-reaching projections to cortex. Whether higher-order cortical regions have the capacity to recruit neuromodulatory systems to aid cognition is unclear. Here, we hypothesized that select cortical regions activate the arousal system, which, in turn, modulates large-scale brain activity, creating a functional circuit predicting cognitive ability. We utilized the Human Connectome Project 7T functional magnetic resonance imaging dataset (n = 149), acquired at rest with simultaneous eye tracking, along with extensive cognitive assessment for each subject. First, we discovered select frontoparietal cortical regions that drive large-scale spontaneous brain activity specifically via engaging the arousal system. Second, we show that the functionality of the arousal circuit driven by bilateral posterior cingulate cortex (associated with the default mode network) predicts subjects' cognitive abilities. This suggests that a cortical region that is typically associated with self-referential processing supports cognition by regulating the arousal system.

Functionality of arousal-regulating brain circuitry at rest predicts human cognitive abilities

Arousal state is regulated by subcortical neuromodulatory nuclei, such as locus coeruleus, which send wide-reaching projections to cortex. Whether higher-order cortical regions have the capacity to recruit neuromodulatory systems to aid cognition is unclear. Here, we hypothesized that select cortical regions activate the arousal system, which in turn modulates large-scale brain activity, creating a functional circuit predicting cognitive ability. We utilized the Human Connectome Project 7T functional magnetic resonance imaging dataset (N=149), acquired at rest with simultaneous eye tracking, along with extensive cognitive assessment for each subject. First, we discovered select frontoparietal cortical regions that drive large-scale spontaneous brain activity specifically via engaging the arousal system. Second, we show that the functionality of the arousal circuit driven by bilateral posterior cingulate cortex (associated with the default mode network) predicts subjects' cognitive abilities. This suggests that a cortical region that is typically associated with self-referential processing supports cognition by regulating the arousal system.

The dose-dependent neuroprotective effect of norepinephrine in improving memory retrieval in an experimental model of multiple sclerosis, experimental autoimmune encephalomyelitis

Multiple sclerosis (MS) is considered an immune-mediated inflammatory disorder that causes cognitive impairments by damaging the hippocampal tissue. Conversely, norepinephrine (NEP) has anti-inflammatory and re-myelinating properties, which improve cognitive impairments. The aim of this study was to assess the neuroprotective effects of NEP on learning and memory disorders in an experimental animal model of MS. Two guide cannulas were bilaterally implanted in the rat hippocampal CA1 regions. After recovery, the animals received 3 μl of 0.01% ethidium bromide (EtB) in each of both hippocampal regions. After three days, the rats were randomly divided into 6 groups (8 rats/group), including control, sham 1, sham 2, and three groups of NEP 0.25, 0.5, and 1 mg/kg by intrahippocampal injection. Behavioral tests (e.g. shuttle box test and open-field test) were then performed. Finally, ROS, MDA, GSH, TNF-α, IL-6, and IL-1β concentrations in the left CA1 area, as well as using western-blot analysis, p-p38, p-JNK, p-AKT, p-ERK1/2, p-NMDA, p-AMPA, p-CREB, and BDNF proteins in the right CA1 region evaluated. The EtB injection increased ROS, MDA, TNF-α, IL-6, and IL-1β levels, as well as p-JNK and p-P38, except all other proteins, while decreasing GSH content, as well as step-through latency and locomotor activity in sham groups compared to the control group. Conversely, NEP (0.5 and 1 mg/kg, particularly at the dose of 1 mg/kg) counterbalanced all the alterations mentioned above in comparison to the sham groups. The EtB induced learning and memory impairment; however, NEP dose-dependently restored these impairments to normal levels.

Large nesting expression in deer mice remains stable under conditions of visual deprivation despite heightened limbic involvement: Perspectives on compulsive-like behavior

Visual stimuli and limbic activation varyingly influence obsessive-compulsive symptom expression and so impact treatment outcomes. Some symptom phenotypes, for example, covert repugnant thoughts, are likely less sensitive to sensory stimuli compared to symptoms with an extrinsic focus, that is, symptoms related to contamination, safety, and "just-right-perceptions." Toward an improved understanding of the neurocognitive underpinnings of obsessive-compulsive psychobiology, work in naturalistic animal model systems is useful. Here, we explored the impact of visual feedback and limbic processes on 24 normal (NNB) and large (LNB) nesting deer mice, respectively (as far as possible, equally distributed between sexes). Briefly, after behavioral classification into either the NNB or LNB cohorts, mice of each cohort were separated into two groups each and assessed for nesting expression under either standard light conditions or conditions of complete visual deprivation (VD). Nesting outcomes were assessed in terms of size and neatness. After nesting assessment completion, mice were euthanized, and samples of frontal-cortical and hippocampal tissues were collected to determine serotonin and noradrenaline concentrations. Our results show that LNB, as opposed to NNB, represents an inflexible and excessive behavioral phenotype that is not dependent on visually guided action-outcome processing, and that it associates with increased frontal-cortical and hippocampal noradrenaline concentrations, irrespective of lighting condition. Collectively, the current results are informing of the neurocognitive underpinnings of nesting behavior. It also provides a valuable foundation for continued investigations into the noradrenergic mechanisms that may influence the development and promulgation of excessive, rigid, and inflexible behaviors.

Psycho-Neuroendocrinology in the Rehabilitation Field: Focus on the Complex Interplay between Stress and Pain

Chronic stress and chronic pain share neuro-anatomical, endocrinological, and biological features. However, stress prepares the body for challenging situations or mitigates tissue damage, while pain is an unpleasant sensation due to nociceptive receptor stimulation. When pain is chronic, it might lead to an allostatic overload in the body and brain due to the chronic dysregulation of the physiological systems that are normally involved in adapting to environmental challenges. Managing stress and chronic pain (CP) in neurorehabilitation presents a significant challenge for healthcare professionals and researchers, as there is no definitive and effective solution for these issues. Patients suffering from neurological disorders often complain of CP, which significantly reduces their quality of life. The aim of this narrative review is to examine the correlation between stress and pain and their potential negative impact on the rehabilitation process. Moreover, we described the most relevant interventions used to manage stress and pain in the neurological population. In conclusion, this review sheds light on the connection between chronic stress and chronic pain and their impact on the neurorehabilitation pathway. Our results emphasize the need for tailored rehabilitation protocols to effectively manage pain, improve treatment adherence, and ensure comprehensive patient care.

The neuromodulatory role of dopamine in improved reaction time by acute cardiovascular exercise

Acute cardiovascular physical exercise improves cognitive performance, as evidenced by a reduction in reaction time (RT). However, the mechanistic understanding of how this occurs is elusive and has not been rigorously investigated in humans. Here, using positron emission tomography (PET) with [11 C]raclopride, in a multi-experiment study we investigated whether acute exercise releases endogenous dopamine (DA) in the brain. We hypothesized that acute exercise augments the brain DA system, and that RT improvement is correlated with this endogenous DA release. The PET study (Experiment 1: n = 16) demonstrated that acute physical exercise released endogenous DA, and that endogenous DA release was correlated with improvements in RT of the Go/No-Go task. Thereafter, using two electrical muscle stimulation (EMS) studies (Experiments 2 and 3: n = 18 and 22 respectively), we investigated what triggers RT improvement. The EMS studies indicated that EMS with moderate arm cranking improved RT, but RT was not improved following EMS alone or EMS combined with no load arm cranking. The novel mechanistic findings from these experiments are: (1) endogenous DA appears to be an important neuromodulator for RT improvement and (2) RT is only altered when exercise is associated with central signals from higher brain centres. Our findings explain how humans rapidly alter their behaviour using neuromodulatory systems and have significant implications for promotion of cognitive health. KEY POINTS: Acute cardiovascular exercise improves cognitive performance, as evidenced by a reduction in reaction time (RT). However, the mechanistic understanding of how this occurs is elusive and has not been rigorously investigated in humans. Using the neurochemical specificity of [11 C]raclopride positron emission tomography, we demonstrated that acute supine cycling released endogenous dopamine (DA), and that this release was correlated with improved RT. Additional electrical muscle stimulation studies demonstrated that peripherally driven muscle contractions (i.e. exercise) were insufficient to improve RT. The current study suggests that endogenous DA is an important neuromodulator for RT improvement, and that RT is only altered when exercise is associated with central signals from higher brain centres.

Assessing hypo-arousal during reward anticipation with pupillometry in patients with major depressive disorder: replication and correlations with anhedonia

Major depressive disorder (MDD) is a devastating and heterogenous disorder for which there are no approved biomarkers in clinical practice. We recently identified anticipatory hypo-arousal indexed by pupil responses as a candidate mechanism subserving depression symptomatology. Here, we conducted a replication and extension study of these findings. We analyzed a replication sample of 40 unmedicated patients with a diagnosis of depression and 30 healthy control participants, who performed a reward anticipation task while pupil responses were measured. Using a Bayesian modelling approach taking measurement uncertainty into account, we could show that the negative correlation between pupil dilation and symptom load during reward anticipation is replicable within MDD patients, albeit with a lower effect size. Furthermore, with the combined sample of 136 participants (81 unmedicated depressed and 55 healthy control participants), we further showed that reduced pupil dilation in anticipation of reward is inversely associated with anhedonia items of the Beck Depression Inventory in particular. Moreover, using simultaneous fMRI, particularly the right anterior insula as part of the salience network was negatively correlated with depressive symptom load in general and anhedonia items specifically. The present study supports the utility of pupillometry in assessing noradrenergically mediated hypo-arousal during reward anticipation in MDD, a physiological process that appears to subserve anhedonia.

Adrenoceptors: A Focus on Psychiatric Disorders and Their Treatments

Research into the involvement of adrenoceptor subtypes in the cause(s) of psychiatric disorders is particularly challenging. This is partly because of difficulties in developing animal models that recapitulate the human condition but also because no evidence for any causal links has emerged from studies of patients. These, and other obstacles, are outlined in this chapter. Nevertheless, many drugs that are used to treat psychiatric disorders bind to adrenoceptors to some extent. Direct or indirect modulation of the function of specific adrenoceptor subtypes mediates all or part of the therapeutic actions of drugs in various psychiatric disorders. On the other hand, interactions with central or peripheral adrenoceptors can also explain their side effects. This chapter discusses both aspects of the field, focusing on disorders that are prevalent: depression, schizophrenia, anxiety, attention-deficit hyperactivity disorder, binge-eating disorder, and substance use disorder. In so doing, we highlight some unanswered questions that need to be resolved before it will be feasible to explain how changes in the function of any adrenoceptor subtype affect mood and behavior in humans and other animals.

Locus Coeruleus and Noradrenergic Pharmacology in Neurodegenerative Disease

Adrenoceptors (ARs) throughout the brain are stimulated by noradrenaline originating mostly from neurons of the locus coeruleus, a brainstem nucleus that is ostensibly the earliest to show detectable pathology in neurodegenerative diseases such as Alzheimer's and Parkinson's diseases. The α1-AR, α2-AR, and β-AR subtypes expressed in target brain regions and on a range of cell populations define the physiological responses to noradrenaline, which includes activation of cognitive function in addition to modulation of neurometabolism, cerebral blood flow, and neuroinflammation. As these heterocellular functions are critical for maintaining brain homeostasis and neuronal health, combating the loss of noradrenergic tone from locus coeruleus degeneration may therefore be an effective treatment for both cognitive symptoms and disease modification in neurodegenerative indications. Two pharmacologic approaches are receiving attention in recent clinical studies: preserving noradrenaline levels (e.g., via reuptake inhibition) and direct activation of target adrenoceptors. Here, we review the expression and role of adrenoceptors in the brain, the preclinical studies which demonstrate that adrenergic stimulation can support cognitive function and cerebral health by reversing the effects of noradrenaline depletion, and the human data provided by pharmacoepidemiologic analyses and clinical trials which together identify adrenoceptors as promising targets for the treatment of neurodegenerative disease.

Exploring the Role of Locus Coeruleus in Alzheimer's Disease: a Comprehensive Update on MRI Studies and Implications

PURPOSE OF REVIEW

Performing a thorough review of magnetic resonance imaging (MRI) studies assessing locus coeruleus (LC) integrity in ageing and Alzheimer's disease (AD), and contextualizing them with current preclinical and neuropathological literature.

RECENT FINDINGS

MRI successfully detected LC alterations in ageing and AD, identifying degenerative phenomena involving this nucleus even in the prodromal stages of the disorder. The degree of LC disruption was also associated with the severity of AD cortical pathology, cognitive and behavioral impairment, and the risk of clinical progression. Locus coeruleus-MRI has proved to be a useful tool to assess the integrity of the central noradrenergic system in vivo in humans. It allowed to test in patients preclinical and experimental hypothesis, thus confirming the specific and marked involvement of the LC in AD and its key pathogenetic role. Locus coeruleus-MRI-related data might represent the theoretical basis on which to start developing noradrenergic drugs to target AD.

Prostaglandin E2 Induces Long-Lasting Inhibition of Noradrenergic Neurons in the Locus Coeruleus and Moderates the Behavioral Response to Stressors

Neuronal activity is modulated not only by inputs from other neurons but also by various factors, such as bioactive substances. Noradrenergic (NA) neurons in the locus coeruleus (LC-NA neurons) are involved in diverse physiological functions, including sleep/wakefulness and stress responses. Previous studies have identified various substances and receptors that modulate LC-NA neuronal activity through techniques including electrophysiology, calcium imaging, and single-cell RNA sequencing. However, many substances with unknown physiological significance have been overlooked. Here, we established an efficient screening method for identifying substances that modulate LC-NA neuronal activity through intracellular calcium ([Ca2+]i) imaging using brain slices. Using both sexes of mice, we screened 53 bioactive substances, and identified five novel substances: gastrin-releasing peptide, neuromedin U, and angiotensin II, which increase [Ca2+]i, and pancreatic polypeptide and prostaglandin D2, which decrease [Ca2+]i Among them, neuromedin U induced the greatest response in female mice. In terms of the duration of [Ca2+]i change, we focused on prostaglandin E2 (PGE2), since it induces a long-lasting decrease in [Ca2+]i via the EP3 receptor. Conditional knock-out of the receptor in LC-NA neurons resulted in increased depression-like behavior, prolonged wakefulness in the dark period, and increased [Ca2+]i after stress exposure. Our results demonstrate the effectiveness of our screening method for identifying substances that modulate a specific neuronal population in an unbiased manner and suggest that stress-induced prostaglandin E2 can suppress LC-NA neuronal activity to moderate the behavioral response to stressors. Our screening method will contribute to uncovering previously unknown physiological functions of uncharacterized bioactive substances in specific neuronal populations.SIGNIFICANCE STATEMENT Bioactive substances modulate the activity of specific neuronal populations. However, since only a limited number of substances with predicted effects have been investigated, many substances that may modulate neuronal activity have gone unrecognized. Here, we established an unbiased method for identifying modulatory substances by measuring the intracellular calcium signal, which reflects neuronal activity. We examined noradrenergic (NA) neurons in the locus coeruleus (LC-NA neurons), which are involved in diverse physiological functions. We identified five novel substances that modulate LC-NA neuronal activity. We also found that stress-induced prostaglandin E2 (PGE2) may suppress LC-NA neuronal activity and influence behavioral outcomes. Our screening method will help uncover previously overlooked functions of bioactive substances and provide insight into unrecognized roles of specific neuronal populations.

SMN deficiency perturbs monoamine neurotransmitter metabolism in spinal muscular atrophy

Beyond motor neuron degeneration, homozygous mutations in the survival motor neuron 1 (SMN1) gene cause multiorgan and metabolic defects in patients with spinal muscular atrophy (SMA). However, the precise biochemical features of these alterations and the age of onset in the brain and peripheral organs remain unclear. Using untargeted NMR-based metabolomics in SMA mice, we identify cerebral and hepatic abnormalities related to energy homeostasis pathways and amino acid metabolism, emerging already at postnatal day 3 (P3) in the liver. Through HPLC, we find that SMN deficiency induces a drop in cerebral norepinephrine levels in overt symptomatic SMA mice at P11, affecting the mRNA and protein expression of key genes regulating monoamine metabolism, including aromatic L-amino acid decarboxylase (AADC), dopamine beta-hydroxylase (DβH) and monoamine oxidase A (MAO-A). In support of the translational value of our preclinical observations, we also discovered that SMN upregulation increases cerebrospinal fluid norepinephrine concentration in Nusinersen-treated SMA1 patients. Our findings highlight a previously unrecognized harmful influence of low SMN levels on the expression of critical enzymes involved in monoamine metabolism, suggesting that SMN-inducing therapies may modulate catecholamine neurotransmission. These results may also be relevant for setting therapeutic approaches to counteract peripheral metabolic defects in SMA.

Anticipatory attractors, functional neurochemistry and "Throw & Catch" mechanisms as illustrations of constructivism

This review explores several rarely discussed examples illustrating constructivism principles, generative and selective features of neuronal regulation of behaviour. First, the review highlights Walter Freeman's experiments and mathematical analysis that uncovered the existence of anticipatory attractors, i.e. non-random dynamical patterns in neurodynamics. Since Freeman's work did not extend to neurochemistry, this paper then points to the proposed earlier neurochemical framework summarizing the managerial roles of monoaminergic, cholinergic and opioid receptor systems likely contributing to anticipatory attractors in line with functional constructivism. As a third example, neurochemistry's evidence points to the "Throw & Catch" (T&C) principle in neurodynamics. This principle refers to the pro-active, neurochemically expensive, massive but topical increase of potentials ("Throw") within electrodynamics and neurotransmission in the brain whenever there is an uncertainty in selection of degrees of freedom (DFs). The T&C also underlines the relay-like processes during the selection of DFs. The "Throw" works as an internally generated "flashlight" that, contrarily to the expectations of entropy reduction, increases entropy and variance observed in processes related to orientation and action-formation. The discussed examples highlight the deficiency of structures-oriented projects and excitation-inhibition concepts in neuroscience. The neural regulation of behaviour appears to be a fluid, constructive process, constantly upgrading the choice of behavioural DFs, to ensure the compatibility between the environmental and individual's individuals' needs and capacities.

Noradrenergic neuromodulation in ageing and disease

The locus coeruleus (LC) is a small brainstem structure located in the lower pons and is the main source of noradrenaline (NA) in the brain. Via its phasic and tonic firing, it modulates cognition and autonomic functions and is involved in the brain's immune response. The extent of degeneration to the LC in healthy ageing remains unclear, however, noradrenergic dysfunction may contribute to the pathogenesis of Alzheimer's (AD) and Parkinson's disease (PD). Despite their differences in progression at later disease stages, the early involvement of the LC may lead to comparable behavioural symptoms such as preclinical sleep problems and neuropsychiatric symptoms as a result of AD and PD pathology. In this review, we draw attention to the mechanisms that underlie LC degeneration in ageing, AD and PD. We aim to motivate future research to investigate how early degeneration of the noradrenergic system may play a pivotal role in the pathogenesis of AD and PD which may also be relevant to other neurodegenerative diseases.

Possible role of locus coeruleus neuronal loss in age-related memory and attention deficits

Introduction

Aging is associated with a decline in cognitive abilities, including memory and attention. It is generally accepted that age-related histological changes such as increased neuroinflammatory glial activity and a reduction in the number of specific neuronal populations contribute to cognitive aging. Noradrenergic neurons in the locus coeruleus (LC) undergo an approximately 20 % loss during ageing both in humans and mice, but whether this change contributes to cognitive deficits is not known. To address this issue, we asked whether a similar loss of LC neurons in young animals as observed in aged animals impairs memory and attention, cognitive domains that are both influenced by the noradrenergic system and impaired in aging.

Methods

For that, we treated young healthy mice with DSP-4, a toxin that specifically kills LC noradrenergic neurons. We compared the performance of DSP-4 treated young mice with the performance of aged mice in models of attention and memory. To do this, we first determined the dose of DSP-4, which causes a similar 20 % neuronal loss as is typical in aged animals.

Results

Young mice treated with DSP-4 showed impaired attention in the presence of distractor and memory deficits in the 5-choice serial reaction time test (5-CSRTT). Old, untreated mice showed severe deficits in both the 5-CSRTT and in fear extinction tests.

Discussion

Our data now suggest that a reduction in the number of LC neurons contributes to impaired working memory and greater distractibility in attentional tasks but not to deficits in fear extinction. We hypothesize that the moderate loss of LC noradrenergic neurons during aging contributes to attention deficits and working memory impairments.

Neural Progenitor Cells and the Hypothalamus

Neural progenitor cells (NPCs) are multipotent neural stem cells (NSCs) capable of self-renewing and differentiating into neurons, astrocytes and oligodendrocytes. In the postnatal/adult brain, NPCs are primarily located in the subventricular zone (SVZ) of the lateral ventricles (LVs) and subgranular zone (SGZ) of the hippocampal dentate gyrus (DG). There is evidence that NPCs are also present in the postnatal/adult hypothalamus, a highly conserved brain region involved in the regulation of core homeostatic processes, such as feeding, metabolism, reproduction, neuroendocrine integration and autonomic output. In the rodent postnatal/adult hypothalamus, NPCs mainly comprise different subtypes of tanycytes lining the wall of the 3^rd ventricle. In the postnatal/adult human hypothalamus, the neurogenic niche is constituted by tanycytes at the floor of the 3^rd ventricle, ependymal cells and ribbon cells (showing a gap-and-ribbon organization similar to that in the SVZ), as well as suprachiasmatic cells. We speculate that in the postnatal/adult human hypothalamus, neurogenesis occurs in a highly complex, exquisitely sophisticated neurogenic niche consisting of at least four subniches; this structure has a key role in the regulation of extrahypothalamic neurogenesis, and hypothalamic and extrahypothalamic neural circuits, partly through the release of neurotransmitters, neuropeptides, extracellular vesicles (EVs) and non-coding RNAs (ncRNAs).

Vagus nerve stimulation: mechanisms and factors involved in memory enhancement

Vagus nerve stimulation (VNS) has been recognized as a useful neuromodulation tool to target the central nervous system by electrical stimulation of peripheral nerves. Activation of the nucleus of the solitary tract (NTS) in the brainstem by vagal afferent nerve fibers allows for modulation of various higher order brain regions, including limbic and cerebral cortex structures. Along with neurological and psychiatric indications, clinical and preclinical studies suggest that VNS can improve memory. While the underlying mechanisms to improve memory with VNS involve brain areas, such as the prefrontal cortex and processes including alertness and arousal, here we focus on VNS-induced memory improvements related to the hippocampus, the main area implicated in memory acquisition. In addition, we detail research demonstrating that a targeted approach to VNS can modify memory outcomes and delve into the molecular mechanisms associated with these changes. These findings indicate that a greater understanding of VNS mechanisms while also considering stimulation parameters, administration site, timing in relation to training, and sex-specific factors, may allow for optimal VNS application to enhance memory.

Divergent projections from locus coeruleus to the corticobasal ganglia system and ventral tegmental area of the adult male zebra finch

The locus coeruleus (LC) is a small noradrenergic brainstem nucleus that plays a central role in regulating arousal, attention, and performance. In the mammalian brain, individual LC neurons make divergent axonal projections to different brain regions, which are distinguished in part by which noradrenaline (NA) receptor subtypes they express. Here, we sought to determine whether similar organizational features characterize LC projections to corticobasal ganglia (CBG) circuitry in the zebra finch song system, with a focus on the basal ganglia nucleus Area X, the thalamic nucleus DLM, as well as the cortical nuclei HVC, LMAN, and RA. Single and dual retrograde tracer injections reveal that single LC-NA neurons make divergent projections to LMAN and Area X, as well as to the dopaminergic VTA/SNc complex that innervates this CBG circuit. Moreover, in situ hybridization revealed that differential expression of mRNA encoding α2A and α2C adrenoreceptors distinguishes LC-recipient CBG song nuclei. Therefore, LC-NA signaling in the zebra finch CBG circuit employs a similar strategy as in mammals, which could allow a relatively small number of LC neurons to exert widespread yet distinct effects across multiple brain regions.

Distribution of α2-Adrenergic Receptors in the Living Human Brain Using [11C]yohimbine PET

The neurofunctional basis of the noradrenergic (NA) system and its associated disorders is still very incomplete because in vivo imaging tools in humans have been missing up to now. Here, for the first time, we use [¹¹C]yohimbine in a large sample of subjects (46 healthy volunteers, 23 females, 23 males; aged 20-50) to perform direct quantification of regional alpha 2 adrenergic receptors' (α₂-ARs) availability in the living human brain. The global map shows the highest [¹¹C]yohimbine binding in the hippocampus, the occipital lobe, the cingulate gyrus, and the frontal lobe. Moderate binding was found in the parietal lobe, thalamus, parahippocampus, insula, and temporal lobe. Low levels of binding were found in the basal ganglia, the amygdala, the cerebellum, and the raphe nucleus. Parcellation of the brain into anatomical subregions revealed important variations in [¹¹C]yohimbine binding within most structures. Strong heterogeneity was found in the occipital lobe, the frontal lobe, and the basal ganglia, with substantial gender effects. Mapping the distribution of α₂-ARs in the living human brain may prove useful not only for understanding the role of the NA system in many brain functions, but also for understanding neurodegenerative diseases in which altered NA transmission with specific loss of α₂-ARs is suspected.

Sleep disorders affect cognitive function in adults: an overview of systematic reviews and meta-analyses

Sleep disorders frequently result in poor memory, attention deficits, as well as a worse prognosis for neurodegenerative changes, such as Alzheimer's disease. The purpose of this study is to investigate the impact of sleep disorders on cognition. We screened four databases for all meta-analyses and systematic reviews from the establishment through March 2022. We have carried out quality evaluation and review the eligible systematic reviews. Evidence grading and quality assessment were performed on 22 eligible articles. Sleep deprivation primarily affects simple attention, complex attention, and working memory in cognition and alertness. The moderate-to-high-quality evidence proves optimal sleep time as 7-8 h. Sleep time outside this range increases the risk of impaired executive function, non-verbal memory, and working memory. Sleep-related breathing disorders is more likely to cause mild cognitive impairment and affects several cognitive domains. In older adults, insomnia primarily affects working memory, episodic memory, inhibitory control, cognitive flexibility, problem-solving, operational ability, perceptual function, alertness, and complex attention, and maintaining sensitivity. Sleep disturbances significantly impair cognitive function, and early detection and intervention may be critical steps in reducing poor prognosis. A simple neuropsychological memory test could be used to screen people with sleep disorders for cognitive impairment.

Supplementary Information

The online version contains supplementary material available at 10.1007/s41105-022-00439-9.

From pupil to the brain: New insights for studying cortical plasticity through pupillometry

Pupil size variations have been associated with changes in brain activity patterns related with specific cognitive factors, such as arousal, attention, and mental effort. The locus coeruleus (LC), a key hub in the noradrenergic system of the brain, is considered to be a key regulator of cognitive control on pupil size, with changes in pupil diameter corresponding to the release of norepinephrine (NE). Advances in eye-tracking technology and open-source software have facilitated accurate pupil size measurement in various experimental settings, leading to increased interest in using pupillometry to track the nervous system activation state and as a potential biomarker for brain disorders. This review explores pupillometry as a non-invasive and fully translational tool for studying cortical plasticity starting from recent literature suggesting that pupillometry could be a promising technique for estimating the degree of residual plasticity in human subjects. Given that NE is known to be a critical mediator of cortical plasticity and arousal, the review includes data revealing the importance of the LC-NE system in modulating brain plasticity and pupil size. Finally, we will review data suggesting that pupillometry could provide a quantitative and complementary measure of cortical plasticity also in pre-clinical studies.

The Central Noradrenergic System in Neurodevelopmental Disorders: Merging Experimental and Clinical Evidence

The aim of this article is to highlight the potential role of the locus-coeruleus-noradrenergic (LC-NA) system in neurodevelopmental disorders (NdDs). The LC is the main brain noradrenergic nucleus, key in the regulation of arousal, attention, and stress response, and its early maturation and sensitivity to perinatal damage make it an interesting target for translational research. Clinical data shows the involvement of the LC-NA system in several NdDs, suggesting a pathogenetic role in the development of such disorders. In this context, a new neuroimaging tool, LC Magnetic Resonance Imaging (MRI), has been developed to visualize the LC in vivo and assess its integrity, which could be a valuable tool for exploring morphological alterations in NdD in vivo in humans. New animal models may be used to test the contribution of the LC-NA system to the pathogenic pathways of NdD and to evaluate the efficacy of NA-targeting drugs. In this narrative review, we provide an overview of how the LC-NA system may represent a common pathophysiological and pathogenic mechanism in NdD and a reliable target for symptomatic and disease-modifying drugs. Further research is needed to fully understand the interplay between the LC-NA system and NdD.

From circuits to behavior: Amygdala dysfunction in fragile X syndrome

Fragile X syndrome (FXS) is a neurodevelopmental disorder caused by a repeat expansion mutation in the promotor region of the FMR1 gene resulting in transcriptional silencing and loss of function of fragile X messenger ribonucleoprotein 1 protein (FMRP). FMRP has a well-defined role in the early development of the brain. Thus, loss of the FMRP has well-known consequences for normal cellular and synaptic development leading to a variety of neuropsychiatric disorders including an increased prevalence of amygdala-based disorders. Despite our detailed understanding of the pathophysiology of FXS, the precise cellular and circuit-level underpinnings of amygdala-based disorders is incompletely understood. In this review, we discuss the development of the amygdala, the role of neuromodulation in the critical period plasticity, and recent advances in our understanding of how synaptic and circuit-level changes in the basolateral amygdala contribute to the behavioral manifestations seen in FXS.

The integrated brain network that controls respiration

Respiration is a brain function on which our lives essentially depend. Control of respiration ensures that the frequency and depth of breathing adapt continuously to metabolic needs. In addition, the respiratory control network of the brain has to organize muscular synergies that integrate ventilation with posture and body movement. Finally, respiration is coupled to cardiovascular function and emotion. Here, we argue that the brain can handle this all by integrating a brainstem central pattern generator circuit in a larger network that also comprises the cerebellum. Although currently not generally recognized as a respiratory control center, the cerebellum is well known for its coordinating and modulating role in motor behavior, as well as for its role in the autonomic nervous system. In this review, we discuss the role of brain regions involved in the control of respiration, and their anatomical and functional interactions. We discuss how sensory feedback can result in adaptation of respiration, and how these mechanisms can be compromised by various neurological and psychological disorders. Finally, we demonstrate how the respiratory pattern generators are part of a larger and integrated network of respiratory brain regions.

Site-Specific knockdown of microglia in the locus coeruleus regulates hypervigilant responses to social stress in female rats

BACKGROUND

Women are at increased risk for psychosocial stress-related anxiety disorders, yet mechanisms regulating this risk are unknown. Psychosocial stressors activate microglia, and the resulting neuroimmune responses that females exhibit heightened sensitivity to may serve as an etiological factor in their elevated risk. However, studies examining the role of microglia during stress in females are lacking.

METHODS

Microglia were manipulated in the stress-sensitive locus coeruleus (LC) of female rats in the context of social stress in two ways. First, intra-LC lipopolysaccharide (LPS; 0 or 3 μg/side, n = 5-6/group), a potent TLR4 agonist and microglial activator, was administered. One hour later, rats were exposed to control or an aggressive social defeat encounter between two males (WS, 15-min). In a separate study, females were treated with intra-LC or intra-central amygdala mannosylated liposomes containing clodronate (m-CLD; 0 or 25 μg/side, n = 13-14/group), a compound toxic to microglia. WS-evoked burying, cardiovascular responses, and sucrose preference were measured. Brain and plasma cytokines were quantified, and cardiovascular telemetry assessed autonomic balance.

RESULTS

Intra-LC LPS augmented the WS-induced burying response and increased plasma corticosterone and interleukin-1β (IL-1β). Further, the efficacy and selectivity of microinjected m-CLD was fully characterized. In the context of WS, intra-LC m-CLD attenuated the hypervigilant burying response during WS as well as the accumulation of intra-LC IL-1β. Intra-central amygdala m-CLD had no effect on WS-evoked behavior.

CONCLUSIONS

These studies highlight an innovative method for depleting microglia in a brain region specific manner and indicate that microglia in the LC differentially regulate hypervigilant WS-evoked behavioral and autonomic responses.

The development of compulsive coping behaviour is associated with a downregulation of Arc in a Locus Coeruleus neuronal ensemble

Some compulsive disorders have been considered to stem from the loss of control over coping strategies, such as displacement. However, the cellular mechanisms involved in the acquisition of coping behaviours and their subsequent compulsive manifestation in vulnerable individuals have not been elucidated. Considering the role of the locus coeruleus (LC) noradrenaline-dependent system in stress and related excessive behaviours, we hypothesised that neuroplastic changes in the LC may be associated with the acquisition of an adjunctive polydipsic water drinking, a prototypical displacement behaviour, and the ensuing development of compulsion in vulnerable individuals. Thus, male Sprague Dawley rats were characterised for their tendency, or not, to develop compulsive polydipsic drinking in a schedule-induced polydipsia (SIP) procedure before their fresh brains were harvested. A new quantification tool for RNAscope assays revealed that the development of compulsive adjunctive behaviour was associated with a low mRNA copy number of the plasticity marker Arc in the LC which appeared to be driven by specific adaptations in an ensemble of tyrosine hydroxylase (TH)+, zif268- neurons. This ensemble was specifically engaged by the expression of compulsive adjunctive behaviour, not by stress, because its functional recruitment was not observed in individuals that no longer had access to the water bottle before sacrifice, while it consistently correlated with the levels of polydipsic water drinking only when it had become compulsive. Together these findings suggest that downregulation of Arc mRNA levels in a population of a TH+/zif268- LC neurons represents a signature of the tendency to develop compulsive coping behaviours.

Adrenoceptors as potential target for add-on immunomodulatory therapy in multiple sclerosis

This review summarizes recent findings related to the role of the sympathetic nervous system (SNS) in pathogenesis of multiple sclerosis (MS) and its commonly used experimental model - experimental autoimmune encephalomyelitis (EAE). They indicate that noradrenaline, the key end-point mediator of the SNS, acting through β-adrenoceptor, has a contributory role in the early stages of MS/EAE development. This stage is characterized by the SNS hyperactivity (increased release of noradrenaline) reflecting the net effect of different factors, such as the disease-associated inflammation, stress, vitamin D hypovitaminosis, Epstein-Barr virus infection and dysbiosis. Thus, the administration of propranolol, a non-selective β-adrenoceptor blocker, readily crossing the blood-brain barrier, to experimental rats before the autoimmune challenge and in the early (preclinical/prodromal) phase of the disease mitigates EAE severity. This phenomenon has been ascribed to the alleviation of neuroinflammation (due to attenuation of primarily microglial activation/proinflammatory functions) and the diminution of the magnitude of the primary CD4+ T-cell autoimmune response (the effect associated with impaired autoantigen uptake by antigen presenting cells and their migration into draining lymph nodes). The former is partly related to breaking of the catecholamine-dependent self-amplifying microglial feed-forward loop and the positive feedback loop between microglia and the SNS, leading to down-regulation of the SNS hyperactivity and its enhancing influence on microglial activation/proinflammatory functions and the magnitude of autoimmune response. The effects of propranolol are shown to be more prominent in male EAE animals, the phenomenon important as males (like men) are likely to develop clinically more severe disease. Thus, these findings could serve as a firm scientific background for formulation of a new sex-specific immune-intervention strategy for the early phases of MS (characterized by the SNS hyperactivity) exploiting anti-(neuro)inflammatory and immunomodulatory properties of propranolol and other relatively cheap and safe adrenergic drugs with similar therapeutic profile.

Catecholaminergic and cholinergic neuromodulation in autism spectrum disorder: A comparison to attention-deficit hyperactivity disorder

Autism spectrum disorder (ASD) is a heterogeneous neurodevelopmental disorder characterized by social impairments and restricted, repetitive behaviors. Treatment of ASD is notoriously difficult and might benefit from identification of underlying mechanisms that overlap with those disturbed in other developmental disorders, for which treatment options are more obvious. One example of the latter is attention-deficit hyperactivity disorder (ADHD), given the efficacy of especially stimulants in treatment of ADHD. Deficiencies in catecholaminergic systems [dopamine (DA), norepinephrine (NE)] in ADHD are obvious targets for stimulant treatment. Recent findings suggest that dysfunction in catecholaminergic systems may also be a factor in at least a subgroup of ASD. In this review we scrutinize the evidence for catecholaminergic mechanisms underlying ASD symptoms, and also include in this analysis a third classic ascending arousing system, the acetylcholinergic (ACh) network. We complement this with a comprehensive review of DA-, NE-, and ACh-targeted interventions in ASD, and an exploratory search for potential treatment-response predictors (biomarkers) in ASD, genetically or otherwise. Based on this review and analysis we propose that (1) stimulant treatment may be a viable option for an ASD subcategory, possibly defined by genetic subtyping; (2) cerebellar dysfunction is pronounced for a relatively small ADHD subgroup but much more common in ASD and in both cases may point toward NE- or ACh-directed intervention; (3) deficiency of the cortical salience network is sizable in subgroups of both disorders, and biomarkers such as eye blink rate and pupillometric data may predict the efficacy of targeting this underlying deficiency via DA, NE, or ACh in both ASD and ADHD.

Cerebral amyloid angiopathy-related cardiac injury: Focus on cardiac cell death

Cerebral amyloid angiopathy (CAA) is a kind of disease in which amyloid β (Aβ) and other amyloid protein deposits in the cerebral cortex and the small blood vessels of the brain, causing cerebrovascular and brain parenchymal damage. CAA patients are often accompanied by cardiac injury, involving Aβ, tau and transthyroxine amyloid (ATTR). Aβ is the main injury factor of CAA, which can accelerate the formation of coronary artery atherosclerosis, aortic valve osteogenesis calcification and cardiomyocytes basophilic degeneration. In the early stage of CAA (pre-stroke), the accompanying locus coeruleus (LC) amyloidosis, vasculitis and circulating Aβ will induce first hit to the heart. When the CAA progresses to an advanced stage and causes a cerebral hemorrhage, the hemorrhage leads to autonomic nervous function disturbance, catecholamine surges, and systemic inflammation reaction, which can deal the second hit to the heart. Based on the brain-heart axis, CAA and its associated cardiac injury can create a vicious cycle that accelerates the progression of each other.

Effects of comorbid posttraumatic stress disorder on cognitive dysfunction in Chinese male methamphetamine patients

OBJECTIVES

Cognitive dysfunction and posttraumatic stress disorder (PTSD) are common in methamphetamine patients. However, few studies have investigated the cognitive performance of methamphetamine patients with PTSD. The purpose of this study was to investigate the impact of comorbid PTSD on cognitive function in Chinese male methamphetamine patients.

METHODS

We analyzed 464 methamphetamine patients and 156 healthy volunteers. The PTSD Screening Scale (PCL-5) was used to assess PTSD and the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) was used to assess cognitive function.

RESULTS

Compared with healthy controls, methamphetamine patients had more cognitive dysfunction in immediate memory, visuospatial/constructional, language, attention and delayed memory. Moreover, methamphetamine patients with PTSD had less cognitive dysfunction in immediate memory, attention, and delayed memory than methamphetamine patients without PTSD. Further stepwise regression analysis showed that PTSD alterations in arousal and reactivity cluster were risk predictors for language, and PTSD negative alteration in cognition and mood cluster were risk predictors for delayed memory.

CONCLUSIONS

Our results indicate that methamphetamine patients without PTSD have poorer cognitive dysfunction than those with PTSD. Some demographic and PTSD symptom clusters are protective or risk factors for cognitive dysfunction in methamphetamine patients.

Measures of tonic and phasic activity of the locus coeruleus-norepinephrine system in children with autism spectrum disorder: An event-related potential and pupillometry study

A growing body of research suggests that locus coeruleus-norepinephrine (LC-NE) system may function differently in individuals with autism spectrum disorder (ASD). Understanding the dynamics of both tonic (resting pupil diameter) and phasic (pupil dilation response [PDR] and event-related potential [ERP]) indices may provide meaningful insights about the nature of LC-NE function in ASD. Twenty-four children with ASD and 27 age- and nonverbal-IQ matched typically developing (TD) children completed two experiments: (1) a resting eye-tracking task to measure tonic pupil diameter, and (2) a three-stimulus oddball paradigm to measure phasic responsivity using PDR and ERP. Consistent with prior reports, our results indicate that children with ASD exhibit increased tonic (resting pupil diameter) and reduced phasic (PDR and ERP) activity of the LC-NE system compared to their TD peers. For both groups, decreased phasic responsivity was associated with increased resting pupil diameter. Lastly, tonic and phasic LC-NE indices were primarily related to measures of attention-deficit/hyperactivity disorder (ADHD), and not ASD, symptomatology. These findings expand our understanding of neurophysiological differences present in ASD and demonstrate that aberrant LC-NE activation may be associated with atypical arousal and decreased responsivity to behaviorally-relevant information in ASD.

Pupil diameter tracked during motor adaptation in humans

Pupil diameter, under constant illumination, is known to reflect individuals' internal states, such as surprise about observation and environmental uncertainty. Despite the growing use of pupillometry in cognitive learning studies as an additional measure for examining internal states, few studies have used pupillometry in human motor learning studies. Here, we provide the first detailed characterization of pupil diameter changes in a short-term reach adaptation paradigm. We measured pupil changes in 121 human participants while they adapted to abrupt, gradual, or switching force field conditions. Sudden increases in movement error caused by the introduction/reversal of the force field resulted in strong phasic pupil dilation during movement accompanied by a transient increase in tonic premovement baseline pupil diameter in subsequent trials. In contrast, pupil responses were reduced when the force field was gradually introduced, indicating that large, unexpected errors drove the changes in pupil responses. Interestingly, however, error-induced pupil responses gradually became insensitive after experiencing multiple force field reversals. We also found an association between baseline pupil diameter and incidental knowledge of the gradually introduced perturbation. Finally, in all experiments, we found a strong co-occurrence of larger baseline pupil diameter with slower reaction and movement times after each rest break. Collectively, these results suggest that tonic baseline pupil diameter reflects one's belief about environmental uncertainty, whereas phasic pupil dilation during movement reflects surprise about a sensory outcome (i.e., movement error), and both effects are modulated by novelty. Our results provide a new approach for nonverbally assessing participants' internal states during motor learning.NEW & NOTEWORTHY Pupil diameter is known as a noninvasive window into individuals' internal states. Despite the growing use of pupillometry in cognitive learning studies, it receives little attention in motor learning studies. Here, we characterized the pupil responses in a short-term reach adaptation paradigm by measuring pupil diameter of human participants while they adapted to abrupt, gradual, or switching force field conditions. Our results demonstrate how surprise and uncertainty reflected in pupil diameter develop during motor adaptation.

Yohimbine as a pharmacological probe for alcohol research: a systematic review of rodent and human studies

Alcohol use disorder (AUD) is a significant public health concern, contributing to a myriad of social, psychological, and physiological issues. Despite substantial efforts within the alcohol research field, promising preclinical findings have failed to translate to clinical use, highlighting the necessity to develop safe and effective pharmacological probes with the ability to be used in preclinical and clinical research. Yohimbine, an α2 adrenergic receptor antagonist, is a well-validated pharmacological tool that has been widely employed in alcohol studies to evaluate noradrenergic activation. This scoping systematic review examines published literature in rodent and human studies involving the use of yohimbine relevant to alcohol research. We conducted a systematic literature review of MEDLINE, Embase, Web of Science Core Collection, CINAHL, PsycInfo, and Cochrane Central Register of Controlled Trials to identify: (1) Experimental Characteristics and Methodology, (2) Sex Differences, (3) Neurochemical Systems and Brain Regions, and (4) Discussion of Applications for Medication Development. Sixty-seven (62 preclinical and 5 clinical) studies were identified meeting the stated criteria, comprising extensive evidence supporting the use of yohimbine as a safe, titratable pharmacological agent for translational alcohol research. Support for the use of yohimbine as a fully translational tool, however, is hindered by limited available findings from human laboratory studies, as well as a dearth of studies examining sex differences in yohimbine's mechanistic actions. Additional consideration should be given to further translational modeling, ideally allowing for parallel preclinical and clinical assessment of yohimbine, methodological assessment of neurochemical systems and brain regions.

The Role of the Paraventricular-Coerulear Network on the Programming of Hypertension by Prenatal Undernutrition

A crucial etiological component in fetal programming is early nutrition. Indeed, early undernutrition may cause a chronic increase in blood pressure and cardiovascular diseases, including stroke and heart failure. In this regard, current evidence has sustained several pathological mechanisms involving changes in central and peripheral targets. In the present review, we summarize the neuroendocrine and neuroplastic modifications that underlie maladaptive mechanisms related to chronic hypertension programming after early undernutrition. First, we analyzed the role of glucocorticoids on the mechanism of long-term programming of hypertension. Secondly, we discussed the pathological plastic changes at the paraventricular nucleus of the hypothalamus that contribute to the development of chronic hypertension in animal models of prenatal undernutrition, dissecting the neural network that reciprocally communicates this nucleus with the locus coeruleus. Finally, we propose an integrated and updated view of the main neuroendocrine and central circuital alterations that support the occurrence of chronic increases of blood pressure in prenatally undernourished animals.

Influence of age and cognitive performance on resting-state functional connectivity of dopaminergic and noradrenergic centers

Aging is associated with structural and functional changes in the brain, with a decline in cognitive functions observed as its inevitable concomitant. The body of literature suggests dopamine and noradrenaline as prominent candidate neuromodulators to mediate these effects; however, knowledge regarding the underlying mechanisms is scarce. To fill this gap, we compared resting-state functional connectivity (FC) patterns of ventral tegmental area (VTA), substantia nigra pars compacta (SNc) and locus coeruleus (LC) in healthy young (20-35 years; N = 37) and older adults (55-80 years; N = 27). Additionally, we sought FC patterns of these structures associated with performance in tasks probing executive, attentional and reward functioning, and we compared the functional coupling of the bilateral SNc. The results showed that individual SNc had stronger coupling with ipsilateral cortical and subcortical areas along with the contralateral cerebellum in the whole sample, and that the strength of connections of this structure with angular gyrus and lateral orbitofrontal cortex predicted visuomotor search abilities. In turn, older age was associated with greater local synchronization within VTA, its lower FC with caudate, mediodorsal thalamus, and SNc, as well as higher FC of both midbrain dopaminergic seeds with red nuclei. LC functional coupling showed no differences between the groups and was not associated with any of the behavioral functions. To the best of our knowledge, this work is the first to report the age-related effects on VTA local synchronization and its connectivity with key recipients of dopaminergic innervation, such as striatum and mediodorsal thalamus.

Mapping the vocal circuitry of Alston's singing mouse with pseudorabies virus

Vocalizations are often elaborate, rhythmically structured behaviors. Vocal motor patterns require close coordination of neural circuits governing the muscles of the larynx, jaw, and respiratory system. In the elaborate vocalization of Alston's singing mouse (Scotinomys teguina) each note of its rapid, frequency-modulated trill is accompanied by equally rapid modulation of breath and gape. To elucidate the neural circuitry underlying this behavior, we introduced the polysynaptic retrograde neuronal tracer pseudorabies virus (PRV) into the cricothyroid and digastricus muscles, which control frequency modulation and jaw opening, respectively. Each virus singly labels ipsilateral motoneurons (nucleus ambiguus for cricothyroid, and motor trigeminal nucleus for digastricus). We find that the two isogenic viruses heavily and bilaterally colabel neurons in the gigantocellular reticular formation, a putative central pattern generator. The viruses also show strong colabeling in compartments of the midbrain including the ventrolateral periaqueductal gray and the parabrachial nucleus, two structures strongly implicated in vocalizations. In the forebrain, regions important to social cognition and energy balance both exhibit extensive colabeling. This includes the paraventricular and arcuate nuclei of the hypothalamus, the lateral hypothalamus, preoptic area, extended amygdala, central amygdala, and the bed nucleus of the stria terminalis. Finally, we find doubly labeled neurons in M1 motor cortex previously described as laryngeal, as well as in the prelimbic cortex, which indicate these cortical regions play a role in vocal production. The progress of both viruses is broadly consistent with vertebrate-general patterns of vocal circuitry, as well as with circuit models derived from primate literature.

The Neuromodulatory Role of the Noradrenergic and Cholinergic Systems and Their Interplay in Cognitive Functions: A Focused Review

The noradrenergic and cholinergic modulation of functionally distinct regions of the brain has become one of the primary organizational principles behind understanding the contribution of each system to the diversity of neural computation in the central nervous system. Decades of work has shown that a diverse family of receptors, stratified across different brain regions, and circuit-specific afferent and efferent projections play a critical role in helping such widespread neuromodulatory systems obtain substantial heterogeneity in neural information processing. This review briefly discusses the anatomical layout of both the noradrenergic and cholinergic systems, as well as the types and distributions of relevant receptors for each system. Previous work characterizing the direct and indirect interaction between these two systems is discussed, especially in the context of higher order cognitive functions such as attention, learning, and the decision-making process. Though a substantial amount of work has been done to characterize the role of each neuromodulator, a cohesive understanding of the region-specific cooperation of these two systems is not yet fully realized. For the field to progress, new experiments will need to be conducted that capitalize on the modular subdivisions of the brain and systematically explore the role of norepinephrine and acetylcholine in each of these subunits and across the full range of receptors expressed in different cell types in these regions.

Spike-Dependent Dynamic Partitioning of the Locus Coeruleus Network through Noradrenergic Volume Release in a Simulation of Nucleus Core

The Locus coeruleus (LC) modulates various neuronal circuits throughout the brain. Its unique architectural organization encompasses a net of axonal innervation that spans the entire brain, while its somatic core is highly compact. Recent research revealed an unexpected cellular input specificity within the nucleus that can give rise to various network states that either broadcast norepinephrine signals throughout the brain or pointedly modulate specific brain areas. Such adaptive input–output functions likely surpass our existing network models that build upon a given synaptic wiring configuration between neurons. As the distances between noradrenergic neurons in the core of the LC are unusually small, neighboring neurons could theoretically impact each other via volume transmission of NE. We therefore set out to investigate if such interaction could be mediated through noradrenergic alpha2-receptors in a spiking neuron model of the LC. We validated our model of LC neurons through comparison with experimental patch-clamp data and identified key variables that impact alpha2-mediated inhibition of neighboring LC neurons. Our simulation confirmed a reliable autoinhibition of LC neurons after episodes of high neuronal activity that continue even after neuronal activity subsided. Additionally, dendro-somatic synapses inhibited spontaneous spiking in the somatic compartment of connected neurons in our model. We determined the exact position of hundreds of LC neurons in the mouse brain stem via a tissue clearing approach and, based on this, further determined that 25 percent of noradrenergic neurons have a neighboring LC neuron within less than a 25-micrometer radius. By modeling NE diffusion, we estimated that more than 15 percent of the alpha2-adrenergic receptors fraction can bind NE within such a diffusion radius. Our spiking neuron model of LC neurons predicts that repeated or long-lasting episodes of high neuronal activity induce partitioning of the gross LC network and reduce the spike rate in neighboring neurons at distances smaller than 25 μm. As these volume-mediating neighboring effects are challenging to test with the current methodology, our findings can guide future experimental approaches to test this phenomenon and its physiological consequences.

Stellate ganglion intervention for chronic pain: A review

Stellate ganglion (SG) intervention is currently widely being studied in many kinds of chronic pain. As one of the convenient ways to treat the sympathetic nervous system, the indications for stellate ganglion intervention (SGI) include complex regional pain syndrome, postherpetic neuralgia, cancer pain of different origins, orofacial pain, and so forth. SGI refers to the reversible or irreversible blocking of the cervical sympathetic trunk, cervical sympathetic ganglion, and their innervation range through noninvasive or minimally invasive treatment. Current treatment options include stellate ganglion block (SGB), SG pulsed radiofrequency, continuous radiofrequency treatment, and noninvasive SGB. In particular, SGB continues to be one of the most studied methods in chronic pain management. However, a single SGB usually provides only short-term effects; repeated SGB may result in complications such as hoarseness, light-headedness, and vessel or nerve injury. Meanwhile, the mechanism of SGI is still unclear. This review discusses the research progress of SGI methods, effectiveness, complications, and possible mechanisms in the management of chronic pain.

Noradrenergic deficits contribute to apathy in Parkinson's disease through the precision of expected outcomes

Apathy is a debilitating feature of many neuropsychiatric diseases, that is typically described as a reduction of goal-directed behaviour. Despite its prevalence and prognostic importance, the mechanisms underlying apathy remain controversial. Degeneration of the locus coeruleus-noradrenaline system is known to contribute to motivational deficits, including apathy. In healthy people, noradrenaline has been implicated in signalling the uncertainty of expectations about the environment. We proposed that noradrenergic deficits contribute to apathy by modulating the relative weighting of prior beliefs about action outcomes. We tested this hypothesis in the clinical context of Parkinson's disease, given its associations with apathy and noradrenergic dysfunction. Participants with mild-to-moderate Parkinson's disease (N = 17) completed a randomised double-blind, placebo-controlled, crossover study with 40 mg of the noradrenaline reuptake inhibitor atomoxetine. Prior weighting was inferred from psychophysical analysis of performance in an effort-based visuomotor task, and was confirmed as negatively correlated with apathy. Locus coeruleus integrity was assessed in vivo using magnetisation transfer imaging at ultra-high field 7T. The effect of atomoxetine depended on locus coeruleus integrity: participants with a more degenerate locus coeruleus showed a greater increase in prior weighting on atomoxetine versus placebo. The results indicate a contribution of the noradrenergic system to apathy and potential benefit from noradrenergic treatment of people with Parkinson's disease, subject to stratification according to locus coeruleus integrity. More broadly, these results reconcile emerging predictive processing accounts of the role of noradrenaline in goal-directed behaviour with the clinical symptom of apathy and its potential pharmacological treatment.