Locus coeruleus-norepinephrine: basic functions and insights into Parkinson's disease

Individual-specific metabolic network based on 18F-FDG PET revealing multi-level aberrant metabolisms in Parkinson's disease

Metabolic network analysis in Parkinson's disease (PD) based on 18F-FDG PET has revealed PD-related metabolic patterns. However, alterations at the systemic metabolic network level and at the connection level between different brain regions still remain unknown. This study aimed to explore metabolic network alterations at multiple network levels among PD patients using an individual-specific metabolic network (ISMN) approach. 18F-FDG-PET images of patients with PD (n = 34) and healthy subjects (n = 47) were collected. Healthy subjects were further separated into reference group (n = 28) and control group (n = 19) randomly. Standardized uptake value normalized by lean body mass ratio (SULr) maps was calculated from the PET images. ISMNs were constructed based on SULr maps for PD patients and controls with reference to the reference group. Comparisons of nodal and edge features were performed between PD and control groups. Correlation analysis was conducted between multilevel network properties and clinical scales in PD group. A linear classifier was trained based on nodal or edge features to distinguish PD from controls. The distance from each patient's ISMN to the group-level difference network showed a negative correlation with Hoehn and Yahr stage (r = -0.390, p = .023). Eight nodes from ISMN were identified which exhibited significantly increased nodal degree in PD patients compared to controls (p < .05). Eleven edges were observed which demonstrated significant distinctions in Z-score values in comparisons to the control group (p < .05). Furthermore, the nodal and edge features showed comparable performances in PD diagnosis compared to the traditional SULr values, with area under the receiver operating characteristic curve larger than 0.91. The proposed ISMN approach revealed systemic metabolic deviations, as well as nodal and edge distinctions in PD, which might be supplementary to the existing findings on PD-related metabolic patterns.

Banisteriopsis caapi extract: Implications for neuroinflammatory pathways in Locus coeruleus lesion rodent model

ETHNOPHARMACOLOGY RELEVANCE

Ayahuasca is a beverage obtained from the decoctions of Banisteriopsis caapi (Spruce ex Griseb.) Morton and Psychotria viridis Ruiz & Pav., used throughout the Amazon as a medicinal beverage for healing and spiritual exploration. The Banisteriopsis caapi extract consists of harmine, harmaline, and tetrahydroharmine (THH); which inhibit the isoforms of monoamine oxidase A and B. In the central nervous system (CNS), it can increase the norepinephrine (NE) concentration, produced in the Locus coeruleus (LC), reducing inflammation that is associated with some neurological disease, such as Parkinson's disease and Alzheimer's disease.

AIM OF THE STUDY

evaluate the effects of treatment with B. caapi extract on the neuroinflammatory profile in animals with selective LC lesions.

MATERIAL AND METHODS

male Wistar rats with LC lesions induced by 6-hydroxydopamine were treated with B. caapi extract. Subsequently, behavioral tests were conducted, including the elevated plus maze, rotarod, and open field. Tyrosine hydroxylase positive (TH+) neurons and IBA-1 positive microglia were quantified from the LC inflammatory markers and free radical products were assessed.

RESULTS

Both 6-Hydroxydopamine hydrochloride and the Banisteriopsis caapi extract causes reduction of LC neurons, at the concentration and frequency used. The LC depletion and the treatment of B. caapi extract interfere with locomotion. B. caapi extract and the LC lesion increased the number and activation of inflammatory cells, such as microglia. B. caapi extract decreases IL-10 in the hippocampus and BDNF gene expression.

CONCLUSION

This study suggests that B. caapi extract (at the concentration and frequency used) promotes noradrenergic neuron depletion and creates a proinflammatory environment in the CNS.

Changes in Noradrenergic Synthesis and Dopamine Beta-Hydroxylase Activity in Response to Oxidative Stress after Iron-induced Brain Injury

Noradrenaline (NA) levels are altered during the first hours and several days after cortical injury. NA modulates motor functional recovery. The present study investigated whether iron-induced cortical injury modulated noradrenergic synthesis and dopamine beta-hydroxylase (DBH) activity in response to oxidative stress in the brain cortex, pons and cerebellum of the rat. Seventy-eight rats were divided into two groups: (a) the sham group, which received an intracortical injection of a vehicle solution; and (b) the injured group, which received an intracortical injection of ferrous chloride. Motor deficits were evaluated for 20 days post-injury. On the 3rd and 20th days, the rats were euthanized to measure oxidative stress indicators (reactive oxygen species (ROS), reduced glutathione (GSH) and oxidized glutathione (GSSG)) and catecholamines (NA, dopamine (DA)), plus DBH mRNA and protein levels. Our results showed that iron-induced brain cortex injury increased noradrenergic synthesis and DBH activity in the brain cortex, pons and cerebellum at 3 days post-injury, predominantly on the ipsilateral side to the injury, in response to oxidative stress. A compensatory increase in contralateral noradrenergic activity was observed, but without changes in the DBH mRNA and protein levels in the cerebellum and pons. In conclusion, iron-induced cortical injury increased the noradrenergic response in the brain cortex, pons and cerebellum, particularly on the ipsilateral side, accompanied by a compensatory response on the contralateral side. The oxidative stress was countered by antioxidant activity, which favored functional recovery following motor deficits.

Early life stress, literacy and dyslexia: an evolutionary perspective

Stress and learning co-evolved in parallel, with their interdependence critical to the survival of the species. Even today, the regulation of moderate levels of stress by the central autonomic network (CAN), especially during pre- and post-natal periods, facilitates biological adaptability and is an essential precursor for the cognitive requisites of learning to read. Reading is a remarkable evolutionary achievement of the human brain, mysteriously unusual, because it is not pre-wired with a genetic address to facilitate its acquisition. There is no gene for reading. The review suggests that reading co-opts a brain circuit centered in the left hemisphere ventral occipital cortex that evolved as a domain-general visual processor. Its adoption by reading depends on the CAN's coordination of the learning and emotional requirements of learning to read at the metabolic, cellular, synaptic, and network levels. By stabilizing a child's self-control and modulating the attention network's inhibitory controls over the reading circuit, the CAN plays a key role in school readiness and learning to read. In addition, the review revealed two beneficial CAN evolutionary adjustments to early-life stress "overloads" that come with incidental costs of school under-performance and dyslexia. A short-term adaptation involving methylation of the FKBP5 and NR3C1 genes is a liability for academic achievement in primary school. The adaptation leading to dyslexia induces alterations in BDNF trafficking, promoting long-term adaptive fitness by protecting against excessive glucocorticoid toxicity but risks reading difficulties by disruptive signaling from the CAN to the attention networks and the reading circuit.

Dose-Ranging Effects of the Intracerebral Administration of Atsttrin in Experimental Model of Parkinson's Disease Induced by 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in Mice

Parkinson's disease is one of the most common neurodegenerative disorders characterized by a multitude of motor and non-motor clinical symptoms resulting from the progressive and long-lasting abnormal loss of nigrostriatal dopaminergic neurons. Currently, the available treatments for patients with Parkinson's disease are limited and exert only symptomatic effects, without adequate signs of delaying or stopping the progression of the disease. Atsttrin constitutes the bioengineered protein which ultrastructure is based on the polypeptide chain frame of the progranulin (PGRN), which exerts anti-inflammatory effects through the inhibition of TNFα. The conducted preclinical studies suggest that the therapeutic implementation of Atsttrin may be potentially effective in the treatment of neurodegenerative diseases that are associated with the occurrence of neuroinflammatory processes. The aim of the proposed study was to investigate the effect of direct bilateral intracerebral administration of Atsttrin using stereotactic methods in the preclinical C57BL/6 mouse model of Parkinson's disease inducted by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) intoxication. The analysis of the dose dependency effects of the increasing doses of Atsttrin has covered a number of parameters and markers regarding neurodegenerative processes and inflammatory responses including IL-1α, TNFα, IL-6, TH, and TG2 mRNA expressions. Accordingly, the evaluation of the changes in the neurochemical profile included DA, DOPAC, 3-MT, HVA, NA, MHPG, 5-HT, and 5-HIAA concentration levels. The intracerebral administration of Atsttrin into the striatum effectively attenuated the neuroinflammatory reaction in evaluated neuroanatomical structures. Furthermore, the partial restoration of monoamine content and its metabolic turnover were observed. In this case, taking into account the previously described pharmacokinetic profile and extrapolated bioavailability as well as the stability characteristics of Atsttrin, an attempt was made to describe as precisely as possible the quantitative and qualitative effects of increasing doses of the compound within the brain tissue microenvironment in the presented preclinical model of the disease. Collectively, this findings demonstrated that the intracerebral administration of Atsttrin may represent a potential novel therapeutic method for the treatment of Parkinson's disease.

Alterations of Cortical Structure and Neurophysiology in Parkinson's Disease Are Aligned with Neurochemical Systems

OBJECTIVE

Parkinson's disease (PD) affects the structural integrity and neurophysiological signaling of the cortex. These alterations are related to the motor and cognitive symptoms of the disease. How these changes are related to the neurochemical systems of the cortex is unknown.

METHODS

We used T1-weighted magnetic resonance imaging (MRI) and magnetoencephalography (MEG) to measure cortical thickness and task-free neurophysiological activity in patients with idiopathic PD (nMEG = 79, nMRI = 65) and matched healthy controls (nMEG = 65, nMRI = 37). Using linear mixed-effects models, we examined the topographical alignment of cortical structural and neurophysiological alterations in PD with cortical atlases of 19 neurotransmitter receptor and transporter densities.

RESULTS

We found that neurophysiological alterations in PD occur primarily in brain regions rich in acetylcholinergic, serotonergic, and glutamatergic systems, with protective implications for cognitive and psychiatric symptoms. In contrast, cortical thinning occurs preferentially in regions rich in noradrenergic systems, and the strength of this alignment relates to motor deficits.

INTERPRETATION

This study shows that the spatial organization of neurophysiological and structural alterations in PD is relevant for nonmotor and motor impairments. The data also advance the identification of the neurochemical systems implicated. The approach uses novel nested atlas modeling methodology that is transferrable to research in other neurological and neuropsychiatric diseases and syndromes. ANN NEUROL 2024;95:802-816.

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.

Exploring Parkinson's Disease-Associated Depression: Role of Inflammation on the Noradrenergic and Serotonergic Pathways

Parkinson's disease (PD) is a multifactorial disease, with genetic and environmental factors contributing to the disease onset. Classically, PD is a movement disorder characterized by the loss of dopaminergic neurons in the nigrostriatal pathway and intraneuronal aggregates mainly constituted of the protein α-synuclein. However, PD patients also display non-motor symptoms, including depression, which have been linked to functional abnormalities of non-dopaminergic neurons, including serotonergic and noradrenergic ones. Thus, through this comprehensive literature review, we shed light on the noradrenergic and serotonergic impairment linked to depression in PD, focusing on the putative involvement of inflammatory mechanisms.

Health phenome of Parkinson's patients reveals prominent mood-sleep cluster

Background

Associations between phenotypic traits, environmental exposures, and Parkinson's disease have largely been evaluated one-by-one, piecemeal, and pre-selections. A comprehensive picture of comorbidities, phenotypes, exposures, and polypharmacy characterizing the complexity and heterogeneity of real-world patients presenting to academic movement disorders clinics in the US is missing.

Objectives

To portrait the complexity of features associated with patients with Parkinson's disease in a study of 933 cases and 291 controls enrolled in the Harvard Biomarkers Study.

Methods

The primary analysis evaluated 64 health features for associations with Parkinson's using logistic regression adjusting for age and sex. We adjusted for multiple testing using the false discovery rate (FDR) with £ 0.05 indicating statistical significance. Exploratory analyses examined feature correlation clusters and feature combinations.

Results

Depression (OR = 3.11, 95% CI 2.1 to 4.71), anxiety (OR = 3.31, 95% CI 2.01-5.75), sleep apnea (OR 2.58, 95% CI 1.47-4.92), and restless leg syndrome (RLS; OR 4.12, 95% CI 1.81-12.1) were significantly more common in patients with Parkinson's than in controls adjusting for age and sex with FDR £ 0.05. The prevalence of depression, anxiety, sleep apnea, and RLS were correlated, and these diseases formed part of a larger cluster of mood traits and sleep traits linked to PD. Exposures to pesticides (OR 1.87, 95% CI 1.37-2.6), head trauma (OR 2.33, 95% CI 1.51-3.73), and smoking (OR 0.57, 95% CI 0.43-0.75) were significantly associated with the disease consistent with previous studies. Vitamin supplementation with cholecalciferol (OR 2.18, 95% CI 1.4-3.45) and coenzyme Q10 (OR 2.98, 95% CI 1.89-4.92) was more commonly used by patients than controls. Cumulatively, 43% (398 of 933) of Parkinson's patients had at least one psychiatric or sleep disorder, compared to 21% (60 of 291) of healthy controls.

Conclusions

43% of Parkinson's patients seen at Harvard-affiliated teaching hospitals have depression, anxiety, and disordered sleep. This syndromic cluster of mood and sleep traits may be pathophysiologically linked and clinically important.

The Gut-Brain Axis in Schizophrenia: The Implications of the Gut Microbiome and SCFA Production

Schizophrenia, a severe mental illness affecting about 1% of the population, manifests during young adulthood, leading to abnormal mental function and behavior. Its multifactorial etiology involves genetic factors, experiences of adversity, infection, and gene-environment interactions. Emerging research indicates that maternal infection or stress during pregnancy may also increase schizophrenia risk in offspring. Recent research on the gut-brain axis highlights the gut microbiome's potential influence on central nervous system (CNS) function and mental health, including schizophrenia. The gut microbiota, located in the digestive system, has a significant role to play in human physiology, affecting immune system development, vitamin synthesis, and protection against pathogenic bacteria. Disruptions to the gut microbiota, caused by diet, medication use, environmental pollutants, and stress, may lead to imbalances with far-reaching effects on CNS function and mental health. Of interest are short-chain fatty acids (SCFAs), metabolic byproducts produced by gut microbes during fermentation. SCFAs can cross the blood-brain barrier, influencing CNS activity, including microglia and cytokine modulation. The dysregulation of neurotransmitters produced by gut microbes may contribute to CNS disorders, including schizophrenia. This review explores the potential relationship between SCFAs, the gut microbiome, and schizophrenia. Our aim is to deepen the understanding of the gut-brain axis in schizophrenia and to elucidate its implications for future research and therapeutic approaches.

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.

The toxic metal hypothesis for neurological disorders

Multiple sclerosis and the major sporadic neurogenerative disorders, amyotrophic lateral sclerosis, Parkinson disease, and Alzheimer disease are considered to have both genetic and environmental components. Advances have been made in finding genetic predispositions to these disorders, but it has been difficult to pin down environmental agents that trigger them. Environmental toxic metals have been implicated in neurological disorders, since human exposure to toxic metals is common from anthropogenic and natural sources, and toxic metals have damaging properties that are suspected to underlie many of these disorders. Questions remain, however, as to how toxic metals enter the nervous system, if one or combinations of metals are sufficient to precipitate disease, and how toxic metal exposure results in different patterns of neuronal and white matter loss. The hypothesis presented here is that damage to selective locus ceruleus neurons from toxic metals causes dysfunction of the blood-brain barrier. This allows circulating toxicants to enter astrocytes, from where they are transferred to, and damage, oligodendrocytes, and neurons. The type of neurological disorder that arises depends on (i) which locus ceruleus neurons are damaged, (ii) genetic variants that give rise to susceptibility to toxic metal uptake, cytotoxicity, or clearance, (iii) the age, frequency, and duration of toxicant exposure, and (iv) the uptake of various mixtures of toxic metals. Evidence supporting this hypothesis is presented, concentrating on studies that have examined the distribution of toxic metals in the human nervous system. Clinicopathological features shared between neurological disorders are listed that can be linked to toxic metals. Details are provided on how the hypothesis applies to multiple sclerosis and the major neurodegenerative disorders. Further avenues to explore the toxic metal hypothesis for neurological disorders are suggested. In conclusion, environmental toxic metals may play a part in several common neurological disorders. While further evidence to support this hypothesis is needed, to protect the nervous system it would be prudent to take steps to reduce environmental toxic metal pollution from industrial, mining, and manufacturing sources, and from the burning of fossil fuels.

Substantia nigral dopamine transporter uptake in dementia with Lewy bodies

Nigrostriatal dopaminergic degeneration is a pathological hallmark of dementia with Lewy bodies (DLB). To identify the subregional dopamine transporter (DAT) uptake patterns that improve the diagnostic accuracy of DLB, we analyzed N-(3-[18F] fluoropropyl)-2β-carbomethoxy-3β-(4-iodophenyl)-nortropane (FP-CIT) PET in 51 patients with DLB, in 36 patients with mild cognitive impairment with Lewy body (MCI-LB), and in 40 healthy controls (HCs). In addition to a high affinity for DAT, FP-CIT show a modest affinity to serotonin or norepinephrine transporters. Specific binding ratios (SBRs) of the nigrostriatal subregions were transformed to age-adjusted z-scores (zSBR) based on HCs. The diagnostic accuracy of subregional zSBRs were tested using receiver operating characteristic (ROC) curve analyses separately for MCI-LB and DLB versus HCs. Then, the effect of subregional zSBRs on the presence of clinical features and gray matter (GM) density were evaluated in all patients with MCI-LB or DLB as a group. ROC curve analyses showed that the diagnostic accuracy of DLB based on the zSBR of substantia nigra (area under the curve [AUC], 0.90) or those for MCI-LB (AUC, 0.87) were significantly higher than that based on the zSBR of posterior putamen for DLB (AUC, 0.72) or MCI-LB (AUC, 0.65). Lower zSBRs in nigrostriatal regions were associated with visual hallucination, severe parkinsonism, and cognitive dysfunction, while lower zSBR of substantia nigra was associated with widespread GM atrophy in DLB and MCI-LB patients. Taken together, our results suggest that evaluation of nigral DAT uptake may increase the diagnostic accuracy of DLB and MCI-LB than other striatal regions.

Disruption of locus coeruleus-related functional networks in Parkinson's disease

Locus coeruleus (LC) is severely affected in Parkinson's Disease (PD). However, alterations in LC-related resting-state networks (RSNs) in PD remain unclear. We used resting-state functional MRI to investigate the alterations in functional connectivity (FC) of LC-related RSNs and the associations between RSNs changes and clinical features in idiopathic rapid eye movement sleep behavior disorder (iRBD) and PD patients with (PD^RBD+) and without RBD (PD^RBD-). There was a similarly disrupted FC pattern of LC-related RSNs in iRBD and PD^RBD+ patients, whereas LC-related RSNs were less damaged in PD^RBD- patients than that in patients with iRBD and PD^RBD+. The FC of LC-related RSNs correlated with cognition and duration in iRBD, depression in PD^RBD-, and cognition and severity of RBD in patients with PD^RBD+. Our findings demonstrate that LC-related RSNs are significantly disrupted in the prodromal stage of α-synucleinopathies and proposed body-first PD (PD^RBD+), but are less affected in brain-first PD (PD^RBD-).

Orexin pathway in Parkinson's disease: a review

Parkinson's disease (PD) is a progressive neurodegenerative disease (NDD) caused by dopaminergic neuron degeneration in the substantia nigra (SN). Orexin is a neuropeptide that plays a role in the pathogenesis of PD. Orexin has neuroprotective properties in dopaminergic neurons. In PD neuropathology, there is also degeneration of orexinergic neurons in the hypothalamus, in addition to dopaminergic neurons. However, the loss of orexinergic neurons in PD began after the degeneration of dopaminergic neurons. Reduced activity of orexinergic neurons has been linked to developing and progressing motor and non-motor symptoms in PD. In addition, the dysregulation of the orexin pathway is linked to the development of sleep disorders. The hypothalamic orexin pathway regulates various aspects of PD neuropathology at the cellular, subcellular, and molecular levels. Finally, non-motor symptoms, particularly insomnia and disturbed sleep, promote neuroinflammation and the accumulation of neurotoxic proteins as a result of defects in autophagy, endoplasmic reticulum (ER) stress, and the glymphatic system. As a result, this review aimed to highlight the potential role of orexin in PD neuropathology.

Locus coeruleus ablation in mice: protocol optimization, stereology and behavioral impact

The Locus Coeruleus (LC) is in the brainstem and supplies key brain structures with noradrenaline, including the forebrain and hippocampus. The LC impacts specific behaviors such as anxiety, fear, and motivation, as well as physiological phenomena that impact brain functions in general, including sleep, blood flow regulation, and capillary permeability. Nevertheless, the short- and long-term consequences of LC dysfunction remain unclear. The LC is among the brain structures first affected in patients suffering from neurodegenerative diseases such as Parkinson's disease and Alzheimer's Disease, hinting that LC dysfunction may play a central role in disease development and progression. Animal models with modified or disrupted LC function are essential to further our understanding of LC function in the normal brain, the consequences of LC dysfunction, and its putative roles in disease development. For this, well-characterized animal models of LC dysfunction are needed. Here, we establish the optimal dose of selective neurotoxin N-(2-chloroethyl)-N-ethyl-bromo-benzylamine (DSP-4) for LC ablation. Using histology and stereology, we compare LC volume and neuron number in LC ablated (LCA) mice and controls to assess the efficacy of LC ablation with different numbers of DSP-4 injections. All LCA groups show a consistent decrease in LC cell count and LC volume. We then proceed to characterize the behavior of LCA mice using a light-dark box test, Barnes maze test, and non-invasive sleep-wakefulness monitoring. Behaviorally, LCA mice differ subtly from control mice, with LCA mice generally being more curious and less anxious compared to controls consistent with known LC function and projections. We note an interesting contrast in that control mice have varying LC size and neuron count but consistent behavior whereas LCA mice (as expected) have consistently sized LC but erratic behavior. Our study provides a thorough characterization of an LC ablation model, firmly consolidating it as a valid model system for the study of LC dysfunction.

Structural and neurophysiological alterations in Parkinson's disease are aligned with cortical neurochemical systems

Parkinson's disease (PD) affects cortical structures and neurophysiology. How these deviations from normative variants relate to the neurochemical systems of the cortex in a manner corresponding to motor and cognitive symptoms is unknown. We measured cortical thickness and spectral neurophysiological alterations from structural magnetic resonance imaging and task-free magnetoencephalography in patients with idiopathic PD (NMEG = 79; NMRI = 65), contrasted with similar data from matched healthy controls (NMEG = 65; NMRI = 37). Using linear mixed-effects models and cortical atlases of 19 neurochemical systems, we found that the structural and neurophysiological alterations of PD align with several receptor and transporter systems (acetylcholine, serotonin, glutamate, and noradrenaline) albeit with different implications for motor and non-motor symptoms. Some neurophysiological alignments are protective of cognitive functions: the alignment of broadband power increases with acetylcholinergic systems is related to better attention function. However, neurochemical alignment with structural and other neurophysiological alterations is associated with motor and psychiatric impairments, respectively. Collectively, the present data advance understanding of the association between the nature of neurophysiological and structural cortical alterations in PD and the symptoms that are characteristic of the disease. They also demonstrate the value of a new nested atlas modeling approach to advance research on neurological and neuropsychiatric diseases.

The Relationships Among Metal Homeostasis, Mitochondria, and Locus Coeruleus in Psychiatric and Neurodegenerative Disorders: Potential Pathogenetic Mechanism and Therapeutic Implications

While alterations in the locus coeruleus-noradrenergic system are present during early stages of neuropsychiatric disorders, it is unclear what causes these changes and how they contribute to other pathologies in these conditions. Data suggest that the onset of major depressive disorder and schizophrenia is associated with metal dyshomeostasis that causes glial cell mitochondrial dysfunction and hyperactivation in the locus coeruleus. The effect of the overactive locus coeruleus on the hippocampus, amygdala, thalamus, and prefrontal cortex can be responsible for some of the psychiatric symptoms. Although locus coeruleus overactivation may diminish over time, neuroinflammation-induced alterations are presumably ongoing due to continued metal dyshomeostasis and mitochondrial dysfunction. In early Alzheimer's and Parkinson's diseases, metal dyshomeostasis and mitochondrial dysfunction likely induce locus coeruleus hyperactivation, pathological tau or α-synuclein formation, and neurodegeneration, while reduction of glymphatic and cerebrospinal fluid flow might be responsible for β-amyloid aggregation in the olfactory regions before the onset of dementia. It is possible that the overactive noradrenergic system stimulates the apoptosis signaling pathway and pathogenic protein formation, leading to further pathological changes which can occur in the presence or absence of locus coeruleus hypoactivation. Data are presented in this review indicating that although locus coeruleus hyperactivation is involved in pathological changes at prodromal and early stages of these neuropsychiatric disorders, metal dyshomeostasis and mitochondrial dysfunction are critical factors in maintaining ongoing neuropathology throughout the course of these conditions. The proposed mechanistic model includes multiple pharmacological sites that may be targeted for the treatment of neuropsychiatric disorders commonly.

Zebrafish Larvae Position Tracker (Z-LaP Tracker): a high-throughput deep-learning behavioral approach for the identification of calcineurin pathway-modulating drugs using zebrafish larvae

Brain function studies greatly depend on quantification and analysis of behavior. While behavior can be imaged efficiently, the quantification of specific aspects of behavior is labor-intensive and may introduce individual biases. Recent advances in deep learning and artificial intelligence-based tools have made it possible to precisely track individual features of freely moving animals in diverse environments without any markers. In the current study, we developed Zebrafish Larvae Position Tracker (Z-LaP Tracker), a modification of the markerless position estimation software DeepLabCut, to quantify zebrafish larval behavior in a high-throughput 384-well setting. We utilized the high-contrast features of our model animal, zebrafish larvae, including the eyes and the yolk for our behavioral analysis. Using this experimental setup, we quantified relevant behaviors with similar accuracy to the analysis performed by humans. The changes in behavior were organized in behavioral profiles, which were examined by K-means and hierarchical cluster analysis. Calcineurin inhibitors exhibited a distinct behavioral profile characterized by increased activity, acoustic hyperexcitability, reduced visually guided behaviors, and reduced habituation to acoustic stimuli. The developed methodologies were used to identify 'CsA-type' drugs that might be promising candidates for the prevention and treatment of neurological disorders.

Acute Hypobaric Hypoxia Exposure Causes Neurobehavioral Impairments in Rats: Role of Brain Catecholamines and Tetrahydrobiopterin Alterations

Hypoxia is a state in which the body or a specific part of the body is deprived of adequate oxygen supply at the tissue level. Sojourners involved in different activities at high altitudes (> 2500 m) face hypobaric hypoxia (HH) due to low oxygen in the atmosphere. HH is an example of generalized hypoxia, where the homeostasis of the entire body of an organism is affected and results in neurochemical changes. It is known that lower O₂ levels affect catecholamines (CA), severely impairing cognitive and locomotor behavior. However, there is less evidence on the effect of HH-mediated alteration in brain Tetrahydrobiopterin (BH4) levels and its role in neurobehavioral impairments. Hence, this study aimed to shed light on the effect of acute HH on CA and BH4 levels with its neurobehavioral impact on Wistar rat models. After HH exposure, significant alteration of the CA levels in the discrete brain regions, viz., frontal cortex, hippocampus, midbrain, and cerebellum was observed. HH exposure significantly reduced spontaneous motor activity, motor coordination, and spatial memory. The present study suggests that the HH-induced behavioral changes might be related to the alteration of the expression pattern of CA and BH4-related genes and proteins in different rat brain regions. Overall, this study provides novel insights into the role of BH4 and CA in HH-induced neurobehavioral impairments.

A whole-brain monosynaptic input connectome to neuron classes in mouse visual cortex

Identification of structural connections between neurons is a prerequisite to understanding brain function. Here we developed a pipeline to systematically map brain-wide monosynaptic input connections to genetically defined neuronal populations using an optimized rabies tracing system. We used mouse visual cortex as the exemplar system and revealed quantitative target-specific, layer-specific and cell-class-specific differences in its presynaptic connectomes. The retrograde connectivity indicates the presence of ventral and dorsal visual streams and further reveals topographically organized and continuously varying subnetworks mediated by different higher visual areas. The visual cortex hierarchy can be derived from intracortical feedforward and feedback pathways mediated by upper-layer and lower-layer input neurons. We also identify a new role for layer 6 neurons in mediating reciprocal interhemispheric connections. This study expands our knowledge of the visual system connectomes and demonstrates that the pipeline can be scaled up to dissect connectivity of different cell populations across the mouse brain.

Potentially toxic elements in the brains of people with multiple sclerosis

Potentially toxic elements such as lead and aluminium have been proposed to play a role in the pathogenesis of multiple sclerosis (MS), since their neurotoxic mechanisms mimic many of the pathogenetic processes in MS. We therefore examined the distribution of several potentially toxic elements in the autopsied brains of people with and without MS, using two methods of elemental bio-imaging. Toxicants detected in the locus ceruleus were used as indicators of past exposures. Autometallography of paraffin sections from multiple brain regions of 21 MS patients and 109 controls detected inorganic mercury, silver, or bismuth in many locus ceruleus neurons of both groups, and in widespread blood vessels, oligodendrocytes, astrocytes, and neurons of four MS patients and one control. Laser ablation-inductively coupled plasma-mass spectrometry imaging of pons paraffin sections from all MS patients and 12 controls showed that combinations of iron, silver, lead, aluminium, mercury, nickel, and bismuth were present more often in the locus ceruleus of MS patients and were located predominantly in white matter tracts. Based on these results, we propose that metal toxicants in locus ceruleus neurons weaken the blood-brain barrier, enabling multiple interacting toxicants to pass through blood vessels and enter astrocytes and oligodendroglia, leading to demyelination.

Early-life low-level lead exposure alters anxiety-like behavior, voluntary alcohol consumption and AC5 protein content in adult male and female C57BL/6 J mice

Despite efforts to eradicate sources of environmental lead (Pb), children, predominately in lower socioeconomic areas, are still frequently exposed to unsafe levels of Pb from soils, dust, and water. Human studies suggest that Pb exposure is associated with altered drug consumption in adults; however, there is limited research at comparable exposure levels (blood Pb levels <10 μg/dL). To model how early-life, low-level Pb exposure affects alcohol consumption in adulthood, we exposed postnatal day (PND) 21 C57Bl/6 J mice to either 30 ppm or 0 ppm Lead (IV) Acetate in distilled water until PND 42, and testing began in adulthood. We predicted that mice with early-life Pb exposure would exhibit greater anxiety-like behavior and consume more alcohol in a three-week Drinking-in-the-Dark procedure (20% v/v) and a 24-h two-bottle choice procedure (10% v/v). We also predicted that Pb exposure would decrease whole-brain content of Adenylate Cyclase-5 (AC5), a protein linked to anxiety-like behaviors and alcohol drinking. There was no difference in limited-access binge-like consumption between exposure groups; however, Pb-exposed mice displayed higher two-bottle choice alcohol intake and preference. Furthermore, Pb-exposed mice exhibited greater anxiety-like behaviors in experiments conducted before an alcohol drinking history but not after. Finally, Pb-exposed mice exhibited an upregulation of whole-brain AC5 protein content. However, this difference was not found in the nucleus accumbens, dorsomedial or dorsolateral striatum. These findings conclude that early-life Pb exposure alters voluntary alcohol consumption and whole-brain AC5 protein content in adulthood. Future studies are necessary to further understand the mechanism behind how Pb exposure alters alcohol intake.

Locus coeruleus and the defensive activation theory of rapid eye movement sleep: A mechanistic perspective

The defensive activation theory (DAT) was recently proposed to explain the biological function of dreaming. Briefly, DAT states that dreams are primarily visual to prevent plastic take-over of an otherwise inactive visual cortex during sleep. Evidence to support the DAT revolve around the interplay between dream activity (REM%) and cortical plasticity found in evolutionary history, primate studies, and coinciding decline in human cortical plasticity and REM% with age. As the DAT may prove difficult to test experimentally, we investigate whether further support for the DAT can be found in the literature. Plasticity and REM sleep are closely linked to functions of the Locus Coeruleus (LC). We therefore review existing knowledge about the LC covering LC stability with age, and the role of the LC in the plasticity of the visual cortex. Recent studies show the LC to be more stable than previously believed and therefore, the LC likely supports the REM% and plasticity in the same manner throughout life. Based on this finding, we review the effect of aging on REM% and visual cortex plasticity. Here, we find that recent, weighty studies are not in complete agreement with the data originally provided as support for DAT. Results from these studies, however, are not in themselves irreconcilable with the DAT. Our findings therefore do not disprove the DAT. Importantly, we show that the LC is involved in all mechanisms central to the DAT. The LC may therefore provide an experimental window to further explore and test the DAT.

High resolution 16S rRNA gene Next Generation Sequencing study of brain areas associated with Alzheimer's and Parkinson's disease

Introduction

Alzheimer's (AD) and Parkinson's disease (PD) are neurodegenerative conditions characterized by incremental deposition of β-amyloid (Aβ) and α-synuclein in AD and PD brain, respectively, in relatively conserved patterns. Both are associated with neuroinflammation, with a proposed microbial component for disease initiation and/or progression. Notably, Aβ and α-synuclein have been shown to possess antimicrobial properties. There is evidence for bacterial presence within the brain, including the oral pathobiont Porphyromonas gingivalis, with cognitive impairment and brain pathology being linked to periodontal (gum) disease and gut dysbiosis.

Methods

Here, we use high resolution 16S rRNA PCR-based Next Generation Sequencing (16SNGS) to characterize bacterial composition in brain areas associated with the early, intermediate and late-stage of the diseases.

Results and discussion

This study reveals the widespread presence of bacteria in areas of the brain associated with AD and PD pathology, with distinctly different bacterial profiles in blood and brain. Brain area profiles were overall somewhat similar, predominantly oral, with some bacteria subgingival and oronasal in origin, and relatively comparable profiles in AD and PD brain. However, brain areas associated with early disease development, such as the locus coeruleus, were substantially different in bacterial DNA content compared to areas affected later in disease etiology.

The Neurodegenerative Elderly Syndrome (NES) hypothesis: Alzheimer and Parkinson are two faces of the same disease

Increasing evidence suggests that Alzheimer's disease (AD) and Parkinson's disease (PD) share monoamine and alpha-synuclein (αSyn) dysfunctions, often beginning years before clinical manifestations onset. The triggers for these impairments and the causes leading these early neurodegenerative processes to become AD or PD remain unclear. We address these issues by proposing a radically new perspective to frame AD and PD: they are different manifestations of one only disease we call "Neurodegenerative Elderly Syndrome (NES)". NES goes through three phases. The seeding stage, which starts years before clinical signs, and where the part of the brain-body affected by the initial αSyn and monoamine dysfunctions, influences the future possible progression of NES towards PD or AD. The compensatory stage, where the clinical symptoms are still silent thanks to compensatory mechanisms keeping monoamine concentrations homeostasis. The bifurcation stage, where NES becomes AD or PD. We present recent literature supporting NES and discuss how this hypothesis could radically change the comprehension of AD and PD comorbidities and the design of novel system-level diagnostic and therapeutic actions.

Temporal model for central sensitization: A hypothesis for mechanism and treatment using systemic manual therapy, a focused review

The purpose of this focused review is to develop a consolidated hypothesis as to the causes and mechanisms of central sensitization and a related model for a treatment approach using Systemic Manual Therapy (SMT). The key to understanding central sensitization is a firm grasp on structure and function of the Locus-coeruleus noradrenaline system (LC-NA). This system uses an elaborate switching mechanism to control the level and rate of activation of multiple systems. This review evaluates the mechanisms and temporal relationships behind four components: salient stimuli, threat coding, aberrant afferent input, and oxidative stress. The five-stage temporal model for central sensitization includes phasic activation of the LC-NA system, salient stimuli, threat coding of salient stimuli, central sensitization, and neural degeneration. The three components of treatment include temporarily reducing afferent visceral input, shifting humoral inflammatory activity away from the brain and outside the body, and reducing oxidative stress by making oxygenated blood more available around the LC and other stressed areas in the brain. The SMT protocols that could help in reduction of visceral afferent input are GUOU, Barral and LAUG. Protocols that should shift humoral inflammatory activity away from the brain or completely out of the body include UD and DCS. One protocol that can potentially reduce oxidative stress by making oxygenated blood more available around the LC is CCCV. Future research and hypothesis-testing strategies as well as limitations are further discussed.

In vivo structural connectome of arousal and motor brainstem nuclei by 7 Tesla and 3 Tesla MRI

Brainstem nuclei are key participants in the generation and maintenance of arousal, which is a basic function that modulates wakefulness/sleep, autonomic responses, affect, attention, and consciousness. Their mechanism is based on diffuse pathways ascending from the brainstem to the thalamus, hypothalamus, basal forebrain and cortex. Several arousal brainstem nuclei also participate in motor functions that allow humans to respond and interact with the surrounding through a multipathway motor network. Yet, little is known about the structural connectivity of arousal and motor brainstem nuclei in living humans. This is due to the lack of appropriate tools able to accurately visualize brainstem nuclei in conventional imaging. Using a recently developed in vivo probabilistic brainstem nuclei atlas and 7 Tesla diffusion‐weighted images (DWI), we built the structural connectome of 18 arousal and motor brainstem nuclei in living humans (n = 19). Furthermore, to investigate the translatability of our findings to standard clinical MRI, we acquired 3 Tesla DWI on the same subjects, and measured the association of the connectome across scanners. For both arousal and motor circuits, our results showed high connectivity within brainstem nuclei, and with expected subcortical and cortical structures based on animal studies. The association between 3 Tesla and 7 Tesla connectivity values was good, especially within the brainstem. The resulting structural connectome might be used as a baseline to better understand arousal and motor functions in health and disease in humans.

Carving the senescent phenotype by the chemical reactivity of catecholamines: An integrative review

Macromolecules damaged by covalent modifications produced by chemically reactive metabolites accumulate in the slowly renewable components of living bodies and compromise their functions. Among such metabolites, catecholamines (CA) are unique, compared with the ubiquitous oxygen, ROS, glucose and methylglyoxal, in that their high chemical reactivity is confined to a limited set of cell types, including the dopaminergic and noradrenergic neurons and their direct targets, which suffer from CA propensities for autoxidation yielding toxic quinones, and for Pictet-Spengler reactions with carbonyl-containing compounds, which yield mitochondrial toxins. The functions progressively compromised because of that include motor performance, cognition, reward-driven behaviors, emotional tuning, and the neuroendocrine control of reproduction. The phenotypic manifestations of the resulting disorders culminate in such conditions as Parkinson's and Alzheimer's diseases, hypertension, sarcopenia, and menopause. The reasons to suspect that CA play some special role in aging accumulated since early 1970-ies. Published reviews address the role of CA hazardousness in the development of specific aging-associated diseases. The present integrative review explores how the bizarre discrepancy between CA hazardousness and biological importance could have emerged in evolution, how much does the chemical reactivity of CA contribute to the senescent phenotype in mammals, and what can be done with it.

Locus Coeruleus in Non-Mammalian Vertebrates

The locus coeruleus (LC) is a vertebrate-specific nucleus and the primary source of norepinephrine (NE) in the brain. This nucleus has conserved properties across species: highly homogeneous cell types, a small number of cells but extensive axonal projections, and potent influence on brain states. Comparative studies on LC benefit greatly from its homogeneity in cell types and modularity in projection patterns, and thoroughly understanding the LC-NE system could shed new light on the organization principles of other more complex modulatory systems. Although studies on LC are mainly focused on mammals, many of the fundamental properties and functions of LC are readily observable in other vertebrate models and could inform mammalian studies. Here, we summarize anatomical and functional studies of LC in non-mammalian vertebrate classes, fish, amphibians, reptiles, and birds, on topics including axonal projections, gene expressions, homeostatic control, and modulation of sensorimotor transformation. Thus, this review complements mammalian studies on the role of LC in the brain.

Locus coeruleus degeneration is associated with disorganized functional topology in Parkinson's disease

Degeneration of the locus coeruleus (LC) is recognized as a critical hallmark of Parkinson's disease (PD). Recent studies have reported that noradrenaline produced from the LC has critical effects on brain functional organization. However, it is unknown if LC degeneration in PD contributes to cognitive/motor manifestations through modulating brain functional organization. This study enrolled 94 PD patients and 68 healthy controls, and LC integrity was measured using the contrast-to-noise ratio of the LC (CNR_LC) calculated from T1-weighted magnetic resonance imaging. We used graph-theory-based network analysis to characterize brain functional organization. The relationships among LC degeneration, network disruption, and cognitive/motor manifestations in PD were assessed. Whether network disruption was a mediator between LC degeneration and cognitive/motor impairments was assessed further. In addition, an independent PD subgroup (n = 35) having functional magnetic resonance scanning before and after levodopa administration was enrolled to evaluate whether LC degeneration-related network deficiencies were independent of dopamine deficiency. We demonstrated that PD patients have significant LC degeneration compared to healthy controls. CNR_LC was positively correlated with Montreal Cognitive Assessment score and the nodal efficiency (NE) of several cognitive-related regions. Lower NE of the superior temporal gyrus was a mediator between LC degeneration and cognitive impairment in PD. However, levodopa treatment could not normalize the reduced NE of the superior temporal gyrus (mediator). In conclusion, we provided evidence for the relationship between LC degeneration and extensive network disruption in PD, and highlight the role of network disorganization in LC degeneration-related cognitive impairment.

Correlations with REM sleep behavior disorder severity in isolated rapid eye movement sleep behavior disorders patients

OBJECTIVES

The pathogenesis of isolated rapid eye movement sleep behavior disorders (iRBD) is poorly understood. The severity of RBD may reflect its pathogenesis.

METHODS

We compared motor function and non-motor symptoms (NMSs) between iRBD patients and healthy volunteers. We correlated motor function, NMSs, and striatal dopaminergic activity with RBD severity using video-polysomnography.

RESULTS

Twenty-one iRBD patients and 17 controls participated. The Unified Parkinson's Disease Rating Scale part III scores were higher in patients compared to controls (p < 0.001). There was no difference in upper extremity function between patients and controls (right, p = 0.220; left, p = 0.209), but gait was slower in iRBD patients (walking time, p < 0.001; number of steps, p < 0.001). The mean value of the Korean version of the Mini-Mental State Exam and Clinical Dementia Rating were lower in patients (p = 0.006, p = 0.003, respectively). Patients with were also more depressed (p = 0.002), had decreased olfactory function (p < 0.001), reported more frequent sleep/fatigue episodes (p < 0.001), worse attention/memory capacity (p < 0.001), gastrointestinal problems (p = 0.009), urinary problems (p = 0.007), and pain (p = 0.083). Further, iRBD patients reported more frequent sleep-related disturbances (p = 0.004), but no difference in daytime sleepiness (p = 0.663). Disease severity was correlated with pain (r = 0.686, p = 0.002) and visuospatial function (r= -0.507, p = 0.038). There were no correlations between RBD severity and striatal dopaminergic activities (p > 0.09).

CONCLUSIONS

iRBD is a multisystem neurodegenerative disorder, and gait abnormalities may be a disease characteristic, possibly related to the akinetic-rigid phenotype of Parkinson's disease. The correlation between pain/visuospatial dysfunction and RBD severity may be related to its pathogenesis.

Autonomic dysfunction and cardiovascular risk in post-traumatic stress disorder

BACKGROUND

Patients with post-traumatic stress disorder (PTSD) have an increased risk for cardiovascular disease. The underlying mechanisms are unclear but impaired autonomic function may contribute. However, research in this field has shown contradictory results and the causal links between PTSD, autonomic dysfunction, and cardiovascular risk remain unknown. This brief review summarizes the current knowledge on alterations in autonomic function and cardiovascular risk in patients with PTSD.

LITERATURE SEARCH STRATEGY

A PubMed search of the literature was performed using the following keywords: autonomic function, heart rate variability, blood pressure variability, sympathetic activity, baroreflex function, and cardiovascular risk in combination with PTSD. Evidence-based studies conducted between 2000 and 2021 were selected.

RESULTS

In total 1221 articles were identified and of these, 61 (48 original research papers, 13 review articles) were included in this review. Many, though not all, studies have reported increased activity of the sympathetic nervous system and decreased activity of the parasympathetic nervous system (namely, autonomic imbalance) in PTSD patients. There seems to be enough evidence to suggest impairments in baroreflex function in PTSD, leading to blood pressure dysregulation. It appears that the chronicity of PTSD diagnosis and symptom severity are independent risk factors for cardiovascular disease, which may be linked with impaired autonomic function.

CONCLUSIONS

Increased cardiovascular risk may be associated with autonomic dysfunction in PTSD. Whether autonomic dysfunction can serve as a biomarker for the onset and progression of PTSD remains to be determined. It also needs to determine if autonomic imbalance increases the risk of developing PTSD.

What substance P might tell us about the prognosis and mechanism of Parkinson's disease?

The neuropeptide substance P (SP) plays an important role in neurodegenerative disorders, among which Parkinson's disease (PD). In the present work we have reviewed the involvement of SP and its preferred receptor (NK1-R) in motor and non-motor PD symptoms, in both PD animal models and patients. Despite PD is primarily a motor disorder, non-motor abnormalities, including olfactory deficits and gastrointestinal dysfunctions, can represent diagnostic PD predictors, according to the hypothesis that the olfactory and the enteric nervous system represent starting points of neurodegeneration, ascending to the brain via the sympathetic fibers and the vagus nerve. In PD patients, the α-synuclein aggregates in the olfactory bulb and the gastrointestinal tract, as well as in the dorsal motor nucleus of the vagus nerve often co-localize with SP, indicating SP-positive neurons as highly vulnerable sites of degeneration. Considering the involvement of the SP/NK1-R in both the periphery and specific brain areas, this system might represent a neuronal substrate for the symptom and disease progression, as well as a therapeutic target for PD.

Methamphetamine abuse disturbs the dopaminergic system to impair hippocampal-based learning and memory: An overview of animal and human investigations

Diverse intellectual functions including memory are some important aspects of cognition. Dopamine is a neurotransmitter of the catecholamine family, which contributes to the experience of pleasure and/or emotional states but also plays crucial roles in learning and memory. Methamphetamine is an illegal drug, the abuse of which leads to long lasting pathological manifestations in the brain. Chronic methamphetamine-induced neurotoxicity results in an alteration of various parts of the memory systems by affecting learning processes, an effect attributed to the structural similarities of this drug with dopamine. An evolving field of research established how cognitive deficits in abusers arise and how they could possibly trigger neurodegenerative disorders. Thus, the drugs-induced tenacious neurophysiological changes of the dopamine system trigger cognitive deficits, thereby affirming the influence of this addictive drug on learning, memory and executive function in human abusers. Here we present an overview of the effects of methamphetamine abuse on cognitive functions, dopaminergic transmission and hippocampal integrity as they have been validated in animals and in humans during the past 20 years.

A Multisubcellular Compartment Model of AMPA Receptor Trafficking for Neuromodulation of Hebbian Synaptic Plasticity

Neuromodulation can profoundly impact the gain and polarity of postsynaptic changes in Hebbian synaptic plasticity. An emerging pattern observed in multiple central synapses is a pull–push type of control in which activation of receptors coupled to the G-protein Gs promote long-term potentiation (LTP) at the expense of long-term depression (LTD), whereas receptors coupled to Gq promote LTD at the expense of LTP. Notably, coactivation of both Gs- and Gq-coupled receptors enhances the gain of both LTP and LTD. To account for these observations, we propose a simple kinetic model in which AMPA receptors (AMPARs) are trafficked between multiple subcompartments in and around the postsynaptic spine. In the model AMPARs in the postsynaptic density compartment (PSD) are the primary contributors to synaptic conductance. During LTP induction, AMPARs are trafficked to the PSD primarily from a relatively small perisynaptic (peri-PSD) compartment. Gs-coupled receptors promote LTP by replenishing peri-PSD through increased AMPAR exocytosis from a pool of endocytic AMPAR. During LTD induction AMPARs are trafficked in the reverse direction, from the PSD to the peri-PSD compartment, and Gq-coupled receptors promote LTD by clearing the peri-PSD compartment through increased AMPAR endocytosis. We claim that the model not only captures essential features of the pull–push neuromodulation of synaptic plasticity, but it is also consistent with other actions of neuromodulators observed in slice experiments and is compatible with the current understanding of AMPAR trafficking.

Mental Resilience and Coping With Stress: A Comprehensive, Multi-level Model of Cognitive Processing, Decision Making, and Behavior

Aversive events can evoke strong emotions that trigger cerebral neuroactivity to facilitate behavioral and cognitive shifts to secure physiological stability. However, upon intense and/or chronic exposure to such events, the neural coping processes can be maladaptive and disrupt mental well-being. This maladaptation denotes a pivotal point when psychological stress occurs, which can trigger subconscious, "automatic" neuroreactivity as a defence mechanism to protect the individual from potential danger including overwhelming unpleasant feelings and disturbing or threatening thoughts.The outcomes of maladaptive neural activity are cognitive dysfunctions such as altered memory, decision making, and behavior that impose a risk for mental disorders. Although the neurocognitive phenomena associated with psychological stress are well documented, the complex neural activity and pathways related to stressor detection and stress coping have not been outlined in detail. Accordingly, we define acute and chronic stress-induced pathways, phases, and stages in relation to novel/unpredicted, uncontrollable, and ambiguous stressors. We offer a comprehensive model of the stress-induced alterations associated with multifaceted pathophysiology related to cognitive appraisal and executive functioning in stress.

Locus Coeruleus Degeneration Correlated with Levodopa Resistance in Parkinson's Disease: A Retrospective Analysis

Background:

The widely divergent responsiveness of Parkinson’s disease (PD) patients to levodopa is an important clinical issue because of its relationship with quality of life and disease prognosis. Preliminary animal experiments have suggested that degeneration of the locus coeruleus (LC) attenuates the efficacy of levodopa treatment.

Objective:

To explore the relationship between LC degeneration and levodopa responsiveness in PD patients in vivo.

Methods:

Neuromelanin-sensitive magnetic resonance imaging (NM-MRI), a good indicator of LC and substantia nigra (SN) degeneration, and levodopa challenge tests were conducted in 57 PD patients. Responsiveness to levodopa was evaluated by the rates of change of the Unified Parkinson’s Disease Rating Scale Part III score and somatomotor network synchronization calculated from resting-state functional MRI before and after levodopa administration. Next, we assessed the relationship between the contrast-to-noise ratio of LC (CNR_LC) and levodopa responsiveness. Multiple linear regression analysis was conducted to rule out the potential influence of SN degeneration on levodopa responsiveness.

Results:

A significant positive correlation was found between CNR_LC and the motor improvement after levodopa administration (R = 0.421, p = 0.004). CNR_LC also correlated with improvement in somatomotor network synchronization (R = –0.323, p = 0.029). Furthermore, the relationship between CNR_LC and levodopa responsiveness was independent of SN degeneration.

Conclusion:

LC degeneration might be an essential factor for levodopa resistance. LC evaluation using NM-MRI might be an alternative tool for predicting levodopa responsiveness and for helping to stratify patients into clinical trials aimed at improving the efficacy of levodopa.

Neurochemistry of Visual Attention

Visual attention is the cognitive process that mediates the selection of important information from the environment. This selection is usually controlled by bottom-up and top-down attentional biasing. Since for most humans vision is the dominant sense, visual attention is critically important for higher-order cognitive functions and related deficits are a core symptom of many neuropsychiatric and neurological disorders. Here, we summarize the importance and relative contributions of different neuromodulators and neurotransmitters to the neural mechanisms of top-down and bottom-up attentional control. We will not only review the roles of widely accepted neuromodulators, such as acetylcholine, dopamine and noradrenaline, but also the contributions of other modulatory substances. In doing so, we hope to shed some light on the current understanding of the role of neurochemistry in shaping neuron properties contributing to the allocation of attention in the visual field.

Associations of Alzheimer's Disease Neuropathologic Changes with Clinical Presentations of Parkinson's Disease

BACKGROUND

Parkinson's disease (PD) and Alzheimer's disease (AD) are the two most prevalent neurodegenerative diseases associated with age. Pathological studies have shown that these two diseases share a certain degree of neuropathological overlap. AD neuropathologic change contributes to cognitive impairment in PD. However, the impact of AD pathology on other clinical phenotypes in PD remains largely unknown.

OBJECTIVE

Herein we aimed to assess the impact of co-occurring AD neuropathologic change on the clinical phenotypes of PD.

METHODS

We examined 46 autopsy brains of PD patients and available clinical information to retrospectively assess the effects of comorbid AD pathology on dementia, hallucinations, and dyskinesia commonly seen in advanced PD.

RESULTS

AD neuropathology significantly increased the risk of hallucinations and dementia, but not dyskinesia in PD patients. Surprisingly, diffuse Lewy body pathology, but not AD pathology, was associated with the occurrence of dementia and hallucinations. Most importantly, we reported that the severity of neuronal loss in the locus coeruleus (LC), but not the severity of neuronal loss in the substantia nigra (SN), was associated with the occurrence of dyskinesia in advanced PD patients, while neither Lewy body scores in SN nor LC had significant effects.

CONCLUSION

We show for the first time that neuronal loss in LC contributes to dyskinesia. Understanding the relationships between the two distinct pathologies and their relevant clinical phenotypes will be crucial in the development of effective disease-modifying therapies for PD.

Optimized Parameters for Transducing the Locus Coeruleus Using Canine Adenovirus Type 2 (CAV2) Vector in Rats for Chemogenetic Modulation Research

Introduction

The locus coeruleus noradrenergic (LC-NA) system is studied for its role in various neurological and psychiatric disorders such as epilepsy and Major Depression Dissorder. Chemogenetics is a powerful technique for specific manipulation of the LC to investigate its functioning. Local injection of AAV2/7 viral vectors has limitations with regards to efficiency and specificity of the transduction, potentially due to low tropism of AAV2/7 for LC neurons. In this study we used a canine adenovirus type 2 (CAV2) vector with different volumes and viral particle numbers to achieve high and selective expression of hM3Dq, an excitatory Designer Receptor Exclusively Activated by Designer Drugs (DREADD), for chemogenetic modulation of LC neurons.

Methods

Adult male Sprague-Dawley rats were injected in the LC with different absolute numbers of CAV2-PRSx8-hM3Dq-mCherry physical particles (0.1E9, 1E9, 5E9,10E9, or 20E9 pp) using different volumes (LowV = 3 nl × 300 nl, MediumV = 3 × 600 nl, HighV = 3 × 1200 nl). Two weeks post-injection, double-labeling immunohistochemistry for dopamine β hydroxylase (DBH) and mCherry was performed to determine hM3Dq expression and its specificity for LC neurons. The size of the transduced LC was compared to the contralateral LC to identify signs of toxicity.

Results

Administration of Medium volume (3 × 600 nl) and 1E9 particles resulted in high expression levels with 87.3 ± 9.8% of LC neurons expressing hM3Dq, but low specificity with 36.2 ± 17.3% of hM3Dq expression in non-LC neurons. The most diluted conditions (Low volume_0.1E pp and Medium Volume_0.1E pp) presented similar high transduction of LC neurons (70.9 ± 12.7 and 77.2 ± 9.8%) with lower aspecificity (5.5 ± 3.5 and 4.0 ± 1.9%, respectively). Signs of toxicity were observed in all undiluted conditions as evidenced by a decreased size of the transduced LC.

Conclusion

This study identified optimal conditions (Low and Medium Volume with 0.1E9 particles of CAV2-PRSx8-hM3Dq-mCherry) for safe and specific transduction of LC neurons with excitatory DREADDs to study the role of the LC-NA system in health and disease.

The Effect of Foot Reflexology on Amnesia in Patients Undergoing Electroconvulsive Therapy: A Randomized Clinical Trial

Introduction: Electroconvulsive therapy (ECT) is the oldest procedure among the early biological treatments introduced in psychiatry. However, the most debated and treatment-limiting adverse effect of ECT is amnesia. Therefore, due to the restriction of the use of drugs to manage amnesia in patients undergoing ECT, the present study investigated the effect of reflexology on amnesia.

Methods: In this randomized controlled trial, 68 patients who met the inclusion criteria were randomly allocated to intervention and control groups. The intervention group received foot reflexology with olive oil 20 minutes a day for 3 days, while the control group was given a gentle foot rub with olive oil 20 minutes a day for 3 days. The amnesia rate of all patients was measured by the Galveston Orientation and Amnesia Test (GOAT) 30 minutes after the end of ECT. The data were analyzed using SPSS software version 11.5 and t-test, chi-squared test, and repeated measures ANOVA.

Results: The results showed that reflexology significantly increased recalling scores in the intervention group compared to the control group. Foot reflexology seems to be effective in managing amnesia in patients after ECT.

Conclusion: Foot reflexology, as a relatively simple, inexpensive, and non-invasive technique with few side effects, can be used to manage amnesia in patients after ECT.

Fixation Duration and Pupil Size as Diagnostic Tools in Parkinson's Disease

BACKGROUND

Visual and oculomotor problems are very common in Parkinson's disease (PD) and by using eye-tracking such problems could be characterized in more detail. However, eye-tracking is not part of the routine clinical investigation of parkinsonism.

OBJECTIVE

To evaluate gaze stability and pupil size in stable light conditions, as well as eye movements during sustained fixation in a population of PD patients and healthy controls (HC).

METHODS

In total, 50 PD patients (66% males) with unilateral to mild-to-moderate disease (Hoehn & Yahr 1-3, Schwab and England 70-90%) and 43 HC (37% males) were included in the study. Eye movements were recorded with Tobii Pro Spectrum, a screen-based eye tracker with a sampling rate of 1200 Hz. Logistic regression analysis was applied to investigate the strength of association of eye-movement measures with diagnosis.

RESULTS

Median pupil size (OR 0.811; 95% CI 0.666-0.987; p = 0.037) and longest fixation period (OR 0.798; 95% CI 0.691-0.921; p = 0.002), were the eye-movement parameters that were independently associated with diagnosis, after adjustment for sex (OR 4.35; 95% CI 1.516-12.483; p = 0.006) and visuospatial/executive score in Montreal Cognitive Assessment (OR 0.422; 95% CI 0.233-0.764; p = 0.004). The area under the ROC curve was determined to 0.817; 95% (CI) 0.732-0.901.

CONCLUSION

Eye-tracking based measurements of gaze fixation and pupil reaction may be useful biomarkers of PD diagnosis. However, larger studies of eye-tracking parameters integrated into the screening of patients with suspected PD are necessary, to further investigate and confirm their diagnostic value.

Elevated norepinephrine metabolism is linked to cortical thickness in the context of Alzheimer's disease pathology

Advanced Alzheimer's disease (AD) is characterized by higher noradrenaline metabolite levels that may be associated with AD pathology. The locus coeruleus (LC) is the main site for cerebral noradrenaline synthesis and LC volume loss occurs as early as Braak stage 1. This study investigates the association between noradrenergic turnover and brain morphology, and the modifying effect of AD pathology. The study sample included 77 memory clinic patients (37 cognitively unimpaired and 40 cognitively impaired (mild cognitive impairment or AD dementia)). Cortical thickness and volumetric analyses were performed using FreeSurfer. Cerebrospinal fluid was analyzed for noradrenergic metabolite 3-methoxy-4-hydroxyphenylethyleneglycol (MHPG), Aβ42 and phosphorylated tau. Higher MHPG was associated with lower cortical thickness and hippocampal volume at lower, but subthreshold, levels of Aβ42 and at higher p-tau levels. These associations remained significant after adding APOE-E4 or cognitive status as covariates. Our results suggest that greater MHPG together with worse AD pathology contributes to neurodegeneration, possibly before significant amyloidosis. The noradrenergic system may play an important role in early detection of AD-related processes.

Efficacy of short-term multidisciplinary intensive rehabilitation in patients with different Parkinson's disease motor subtypes: a prospective pilot study with 3-month follow-up

Parkinson's disease (PD) can be classified into three motor-based subtypes: postural instability/gait difficulty (PIGD), tremor dominant (TD), and indeterminate. The neuropathophysiological mechanisms of the three motor subtypes are different, which may lead to different responses to therapy. Sixty-nine patients with idiopathic Parkinson's disease (Hoehn-Yahr stage ≤ 3) were screened from 436 patients with Parkinsonism recruited through outpatient services and the internet. According to the Movement Disorder Society Unified Parkinson's Disease Rating Scale (MDS-UPDRS) TD/PIGD ratio, the patients were divided into PIGD (TD/PIGD ≤ 0.09; n = 36), TD (TD/PIGD ≥1.15; n = 19), and indeterminate (TD/PIGD = 0.90-1.15; n = 14) groups. All patients received 2 weeks of multidisciplinary intensive rehabilitation treatment (MIRT) during hospitalization, as well as a remote home rehabilitation health education class. Compared with the scores at admission, all patients showed significant improvements in their MDS-UPDRS III score, walking ability, balance, and posture control at discharge. Moreover, the MDS-UPDRS III score improvement was greater in the PIGD group than in the TD group. The follow-up data, collected for 3 months after discharge, showed that overall symptom improvement in each group was maintained for 1-3 months. Furthermore, there were no significant differences in the duration or grade effects of symptom improvement among the three groups. These findings suggest that 2 weeks of MIRT is effective for improving motor performance in all three motor subtypes. Patients in the PIGD group had a better response after hospitalization than those in the TD group. This study was approved by the Institutional Ethics Committee of Beijing Rehabilitation Hospital of Capital Medical University of China (approval No. 2018bkky022) on May 7, 2018 and registered with the Chinese Clinical Trial Registry (registration No. ChiCTR1900020771) on January 19, 2019.

Uncovering the locus coeruleus: Comparison of localization methods for functional analysis

Functional neuroimaging of small brainstem structures in humans is gaining interest due to their potential importance in aging and many clinical conditions. Researchers have used different methods to measure activity in the locus coeruleus (LC), the main noradrenergic nucleus in the brain. However, the extent to which these different LC localization methods yield similar results is unclear. In the present article, we compared four different approaches to estimate localization of the LC in a large sample (N = 98): 1) a probabilistic map from a previous study, 2) masks segmented from neuromelanin-sensitive scans, both manually and semi-automatically, 3) components from a masked-independent components analysis of the functional data, and 4) a mask from pupil regression of the functional data. The four methods have all been used previously in the imaging community to localize the LC in vivo in humans. We report several measures of similarity between the LC masks obtained from the different methods. In addition, we compare functional connectivity maps obtained from the different masks. We conclude that sample-specific masks appear more suitable than masks obtained from an independent sample, that masks based on structural versus functional methods may capture different portions of LC, and that, at the group level, the creation of a "consensus" mask using more than one approach may give a better estimate of LC localization.