Acetylcholine-dopamine interactions in the pathophysiology and treatment of CNS disorders

Free water imaging reveals asynchronous dopaminergic degeneration in substantia nigra and ventral tegmental area in prodromal and early Parkinson's disease

PURPOSE

The ventral tegmental area (VTA), which is rich in dopaminergic neurons, may play a role in influencing clinical symptoms in Parkinson's Disease (PD). However, the degeneration dynamics of the VTA during the early and prodromal stages of PD remain unclear. This study aims to explore microstructural changes in the VTA among prodromal PD patients with idiopathic REM sleep behavior disorder (iRBD) and early-stage PD patients using free water imaging (FWI) to assess free water (FW) and its correlation with clinical symptoms.

METHOD

Diffusion tensor imaging data from 238 participants, including 69 healthy controls (HC), 54 iRBD patients, and 115 PD patients. FW values were computed using a bi-tensor model, and comparisons were done between the HC, iRBD, and PD groups. Additionally, the relationship between FW values in the VTA and substantia nigra pars compacta (SNc) and clinical symptoms was explored through baseline assessments and longitudinal tracking of iRBD patients.

RESULTS

FW values in the SNc significantly increased in iRBD and PD patients compared to HC, with the PD group exhibiting even higher FW values. Initially, the FW values in the VTA in iRBD patients did not significantly differ from those of HC but increased in early PD, correlating with anxiety and motor deficits. Longitudinal tracking revealed FW increases in the SNc and VTA in iRBD patients over time.

CONCLUSION

The present findings revealed a desynchronized degeneration pattern between the VTA and SNc, with no degeneration observed in the prodromal phase but gradual changes over time, leading to pronounced VTA degeneration in early PD. This underscores the impact of early VTA changes on PD symptoms, contributing to understanding of PD pathophysiology.

Effect of hexyloxy position on antagonistic properties of KH-5 (1-{2-[4-(hexyloxy)benzoyloxy]ethyl}-1-methyl-1,2,3,6-tetrahydropyridin-1-ium iodide) at muscarinic acetylcholine receptors

Antagonists with a long residence time at the receptors are desired for the possibility of reducing daily doses and side effects. KH-5 (1-{2-[4-(hexyloxy)benzoyloxy]ethyl}-1-methyl-1,2,3,6-tetrahydropyridin-1-ium iodide) is the long-acting M1-preferring bitopic muscarinic antagonist with a half-life at muscarinic receptors of up to five hours. The binding of 2-hexyloxy and 3-hexyloxy analogues of KH-5 was simulated in silico, compounds were synthesized and their binding and antagonistic properties were measured experimentally in CHO cells expressing individual subtypes of muscarinic acetylcholine receptors. The overall binding affinities of the new compounds were similar to their respective parent compounds. Shifting the hexyloxy chain to ortho and meta positions led to a decrease in potency at the M1 receptor but an increase in potency at the M2 receptor and abolition of long-term antagonism. Preservation of the para position of the hexyloxy chain is essential for the further development of M1-preferring antagonists. Modifications of the basic centre may be the way to improve the geometry of antagonists towards long residence times to obtain the desired long-acting muscarinic antagonists in the future. The additional challenge for further development is the low metabolic stability of compounds.

Efficacy and acceptability of pharmacological interventions for tardive dyskinesia in people with schizophrenia or mood disorders: a systematic review and network meta-analysis

Tardive Dyskinesia (TD) can occur in people exposed to dopamine receptor antagonists (DRAs). Its clinical management remains challenging. We conducted a systematic review/random-effects network meta-analysis (NMA) searching PubMed/MEDLINE/PsycINFO/ClinicalTrials.gov/Cochrane Central Register (22/05/2023, pre-defined protocol https://osf.io/b52ae/ ), for randomized controlled trials (RCTs) of pharmacological/brain stimulation interventions for DRA-induced TD in adults with schizophrenia or mood disorders. Primary outcomes were TD symptom change (standardized mean difference/SMD) and all-cause discontinuation (acceptability-risk ratio/RR). Sensitivity analyses were conducted. Global, local inconsistencies, risk of bias (RoB-2 tool), and confidence in evidence (CINeMA) were measured. We included 46 trials (n = 2844, age = 52.89 ± 9.94 years, males = 59.8%, schizophrenia = 84.6%, mood disorders = 15.4%), all testing pharmacological interventions versus placebo. We identified three subnetworks. In network 1, several treatments outperformed placebo on TD symptoms with large effect sizes (k = 34, n = 2269), encompassing 22 interventions versus placebo, but 18 had 1 RCTs only, and 15 had n ≤ 20. High heterogeneity (I2 = 57.1%; tau2 = 0.0797), and global inconsistency (Q = 32.64; df = 14; p = 0.0032) emerged. No significant differences emerged in acceptability. When restricting analyses to treatments with trials with n > 20 and >1 RCT, only valbenazine (k = 5, SMD = -0.69; 95% CI = -1.00, -0.37) and vitamin E (k = 7, SMD = -0.49; 95% CI = -0.87, -0.11) were superior to placebo. Deutetrabenazine outperformed placebo considering AIMS score and in low risk of bias trials only and with a moderate effect size for 24/36 mg (k = 2, SMD = -0.57/-0.60). Confidence in findings was low for deutetrabenazine and valbenazine, very low for all others. In network 2 (k = 2, n = 63), switch to molindone (k = 1, n = 9) versus switch to haloperidol worsened TD (SMD = 1.68; 95% CI = 0.61,2.76). In network 3 (k = 3, n = 194), antipsychotic wash-out+placebo (k = 1, n = 25) versus TAU+placebo (k = 1, n = 27) worsened TD (SMD = 1.30; 95% CI = 0.36,2.23). Despite large effect sizes for some treatments with very low quality/confidence, when considering higher quality evidence only valbenazine or deutetrabenazine are evidence-based first-line treatments for TD, and potentially vitamin E as second-line. Switching to molindone and antipsychotic washout should be avoided. More treatment options and higher-quality trials are needed.

Effects of kratom alkaloids on mesolimbic dopamine release

Kratom is derived from the leaves of a plant (Mitragyna speciosa) native to Southeast Asia that has been consumed for its complex stimulant-like effects at low doses, opiate-like effects at high doses, to treat mood related issues like anxiety or depression, or to help ameliorate opioid withdrawal symptoms. However, the neural mechanisms of its major psychoactive alkaloids, mitragynine (MG) and 7-hydroxymitragynine (7-HMG), are still not clear. Given that the effects of kratom are often compared to drugs with abuse liabilities, the current study examined the effects of MG and 7-HMG on reward-related neurotransmission. Fixed potential amperometry was used to quantify stimulation-evoked phasic dopamine release in the nucleus accumbens (NAc) of anesthetized male and female mice before and after MG (1, 15, or 30 mg/kg i.p.), 7-HMG (0.5, 1, or 2 mg/kg i.p.), or vehicle. MG reduced dopamine release over the recording period (90 min) in a dose dependent manner, and the low dose of MG significantly increased dopamine autoreceptor functioning in males. Both sexes responded similarly to 7-HMG with the low dose of 7-HMG increasing dopamine release while the high dose decreased dopamine release. 7-HMG did not alter dopamine autoreceptor functioning for either sex. Neither MG nor 7-HMG altered the clearance rate of stimulation-evoked dopamine. Findings suggest that these kratom alkaloids do alter dopamine functioning, although potentially not in a way consistent with classic drugs of abuse. Further investigation of the neural mechanisms of kratom's alkaloids will provide crucial and urgent insight into their therapeutic uses or potential abuse liability.

In-silico Studies and Antioxidant and Neuroprotective Assessment of Microencapsulated Celecoxib against Scopolamine-induced Alzheimer's Disease

BACKGROUND AND OBJECTIVE

Alzheimer's disease (AD) is an enervating and chronic progressive neurodegenerative disorder. Celecoxib (CXB) possesses efficacious antioxidants and has neuroprotective, anti-inflammatory, and immunomodulatory properties. However, the poor bioavailability of CXB limits its therapeutic utility. Thus, this study aimed to evaluate the microencapsulated celecoxib MCXB for neuroprotection.

METHODOLOGY

CXB was screened by molecular docking study using AutoDock (version 5.2), and the following proteins, such as 4EY7, 2HM1, 2Z5X, and 1PBQ were selected for predicting its neuroprotective effect. Scopolamine 20 mg/kg/day for approximately 7 days was administered to albino rats. Pure CXB 100 mg/kg/- day and 200 mg/kg/day, and MCXB 100 mg/kg/day and 200 mg/kg/day were administered, respectively. Further, to assess the oxidative stress, the nitric oxide (NO), superoxide dismutase (SOD), catalase, and lipid peroxidation (LPO) were evaluated using chemical methods. The neurochemical biomarkers like AChE, glutamate, and dopamine were evaluated using the ELISA method. Further, the histopathology of brain cells was carried out to assess the neuro-regeneration and neurodegeneration of the neurons.

RESULTS

There was a significant binding interaction of CXB (score -6.3, -6.5, -5.1, -9.1) and donepezil (score- 5.5, -7.6, -7.0, and -8.6) with AchE (4EY7), β-secretase (2HM1, monoamine oxidase (2Z5X), and glutamate (1PBQ), respectively. MCXB-treated rats (100 mg/kg/day, 200 mg/kg/day) showed increased SOD levels (p < 0.001), whereas NO, catalase, and LPO levels were significantly (p < 0.001) decreased as compared to scopolamine-treated rats. Further, MCXB-treated rats showed a modulatory effect in the level of dopamine and AchE. However, the glutamate level was significantly (p < 0.001) decreased.

CONCLUSION

In addition to that, histopathological examination of the hippocampus part showed remarkable improvement in brain cells. So, the findings of the results revealed that MCXB, in a dose-dependent manner, showed a neuroprotective effect against scopolamine-induced AD. This effect may be attributed to the activation of cholinergic pathways.

Striatal Cholinergic Interneurons Control Physical Nicotine Withdrawal via Muscarinic Receptor Signaling

Striatal cholinergic interneurons (ChIs) provide acetylcholine tone to the striatum and govern motor functions. Nicotine withdrawal elicits physical symptoms that dysregulate motor behavior. Here, the role of striatal ChIs in physical nicotine withdrawal is investigated. Mice under RNAi-dependent genetic inhibition of striatal ChIs (ChIGI) by suppressing the sodium channel subunit NaV1.1, lessening action potential generation and activity-dependent acetylcholine release is first generated. ChIGI markedly reduced the somatic signs of nicotine withdrawal without affecting other nicotine-dependent or striatum-associated behaviors. Multielectrode array (MEA) recording revealed that ChIGI reversed ex vivo nicotine-induced alterations in the number of neural population spikes in the dorsal striatum. Notably, the drug repurposing strategy revealed that a clinically-approved antimuscarinic drug, procyclidine, fully mimicked the therapeutic electrophysiological effects of ChIGI. Furthermore, both ChIGI and procyclidine prevented the nicotine withdrawal-induced reduction in striatal dopamine release in vivo. Lastly, therapeutic intervention with procyclidine dose-dependently diminished the physical signs of nicotine withdrawal. The data demonstrated that the striatal ChIs are a critical substrate of physical nicotine withdrawal and that muscarinic antagonism holds therapeutic potential against nicotine withdrawal.

p-Coumaric acid potential in restoring neuromotor function and oxidative balance through the Parkin pathway in a Parkinson disease-like model in Drosophila melanogaster

p-Coumaric acid is a significant phenolic compound known for its potent antioxidant activity. Thus, this study investigated the effects of p-coumaric acid on the behavioral and neurochemical changes induced in Drosophila melanogaster by exposure to rotenone in a Parkinson disease (PD)-like model. The flies were divided into four groups and maintained for seven days on different diets: a standard diet (control), a diet containing rotenone (500 μM), a control diet to which p-coumaric acid was added on the fourth day (0.3 μM), and a diet initially containing rotenone (500 μM) with p-coumaric acid added on the fourth day (0.3 μM). Exposure to p-coumaric acid ameliorated locomotor impairment and reduced mortality induced by rotenone. Moreover, p-coumaric acid normalized oxidative stress markers (ROS, TBARS, SOD, CAT, GST, and NPSH), mitigated oxidative damage, and reflected in the recovery of dopamine levels, AChE activity, and cellular viability post-rotenone exposure. Additionally, p-coumaric acid restored the immunoreactivity of Parkin and Nrf2. The results affirm that p-coumaric acid effectively mitigates PD-like model-induced damage, underscoring its antioxidant potency and potential neuroprotective effect.

Influence of terahertz waves on the binding of choline to choline acetyltransferase: insights from molecular dynamics simulations

Acetylcholine (Ach) is a common neurotransmitter in the central nervous system (CNS) and peripheral nervous system (PNS). It is one of the neurotransmitters in the autonomic nervous system and the main neurotransmitter in all autonomic ganglia. Experiments have confirmed that electromagnetic waves can affect the synthesis of animal neurotransmitters, but the microscopic effects of electromagnetic waves in the terahertz (THz) frequency band are still unclear. Based on density functional theory (DFT) and molecular dynamics (MD) simulation methods, this paper studies the effect of THz electromagnetic waves on the binding of choline to choline acetyltransferase (ChAT). By emitting THz waves that resonate with the characteristic vibration mode of choline near the active site, it was found that THz waves with a frequency of 45.3 THz affected the binding of choline to ChAT, especially the binding of the active site histidine His324 to choline. The main evidence is that under the action of THz waves, the binding free energy of choline to histidine His324 and ChAT at the active site was significantly reduced compared to noE, which may have a potential impact on the enzymatic synthesis of Ach. It is expected to achieve the purpose of regulating the synthesis of the neurotransmitter Ach under the action of THz waves and treat certain nervous system diseases.

Emotional vocalizations alter behaviors and neurochemical release into the amygdala

The basolateral amygdala (BLA), a brain center of emotional expression, contributes to acoustic communication by first interpreting the meaning of social sounds in the context of the listener's internal state, then organizing the appropriate behavioral responses. We propose that modulatory neurochemicals such as acetylcholine (ACh) and dopamine (DA) provide internal-state signals to the BLA while an animal listens to social vocalizations. We tested this in a vocal playback experiment utilizing highly affective vocal sequences associated with either mating or restraint, then sampled and analyzed fluids within the BLA for a broad range of neurochemicals and observed behavioral responses of adult male and female mice. In male mice, playback of restraint vocalizations increased ACh release and usually decreased DA release, while playback of mating sequences evoked the opposite neurochemical release patterns. In non-estrus female mice, patterns of ACh and DA release with mating playback were similar to males. Estrus females, however, showed increased ACh, associated with vigilance, as well as increased DA, associated with reward-seeking. Experimental groups that showed increased ACh release also showed the largest increases in an aversive behavior. These neurochemical release patterns and several behavioral responses depended on a single prior experience with the mating and restraint behaviors. Our results support a model in which ACh and DA provide contextual information to sound analyzing BLA neurons that modulate their output to downstream brain regions controlling behavioral responses to social vocalizations.

The mesopontine tegmentum in reward and aversion: From cellular heterogeneity to behaviour

The mesopontine tegmentum, comprising the pedunculopontine tegmentum (PPN) and the laterodorsal tegmentum (LDT), is intricately connected to various regions of the basal ganglia, motor systems, and limbic systems. The PPN and LDT can regulate the activity of different brain regions of these target systems, and in this way are in a privileged position to modulate motivated behaviours. Despite recent findings, the PPN and LDT have been largely overlooked in discussions about the neural circuits associated with reward and aversion. This review aims to provide a timely and comprehensive resource on past and current research, highlighting the PPN and LDT's connectivity and influence on basal ganglia and limbic, and motor systems. Seminal studies, including lesion, pharmacological, and optogenetic/chemogenetic approaches, demonstrate their critical roles in modulating reward/aversive behaviours. The review emphasizes the need for further investigation into the associated cellular mechanisms, in order to clarify their role in behaviour and contribution for different neuropsychiatric disorders.

Normative modelling of molecular-based functional circuits captures clinical heterogeneity transdiagnostically in psychiatric patients

Advanced methods such as REACT have allowed the integration of fMRI with the brain's receptor landscape, providing novel insights transcending the multiscale organisation of the brain. Similarly, normative modelling has allowed translational neuroscience to move beyond group-average differences and characterise deviations from health at an individual level. Here, we bring these methods together for the first time. We used REACT to create functional networks enriched with the main modulatory, inhibitory, and excitatory neurotransmitter systems and generated normative models of these networks to capture functional connectivity deviations in patients with schizophrenia, bipolar disorder (BPD), and ADHD. Substantial overlap was seen in symptomatology and deviations from normality across groups, but these could be mapped into a common space linking constellations of symptoms through to underlying neurobiology transdiagnostically. This work provides impetus for developing novel biomarkers that characterise molecular- and systems-level dysfunction at the individual level, facilitating the transition towards mechanistically targeted treatments.

Drug Development for Alzheimer's and Parkinson's Disease: Where Do We Go Now?

Neurodegenerative diseases (NDs) are a set of progressive, chronic, and incurable diseases characterized by the gradual loss of neurons, culminating in the decline of cognitive and/or motor functions. Alzheimer's disease (AD) and Parkinson's disease (PD) are the most common NDs and represent an enormous burden both in terms of human suffering and economic cost. The available therapies for AD and PD only provide symptomatic and palliative relief for a limited period and are unable to modify the diseases' progression. Over the last decades, research efforts have been focused on developing new pharmacological treatments for these NDs. However, to date, no breakthrough treatment has been discovered. Hence, the development of disease-modifying drugs able to halt or reverse the progression of NDs remains an unmet clinical need. This review summarizes the major hallmarks of AD and PD and the drugs available for pharmacological treatment. It also sheds light on potential directions that can be pursued to develop new, disease-modifying drugs to treat AD and PD, describing as representative examples some advances in the development of drug candidates targeting oxidative stress and adenosine A2A receptors.

eIF2α phosphorylation evokes dystonia-like movements with D2-receptor and cholinergic origin and abnormal neuronal connectivity

Dystonia is the 3rd most common movement disorder. Dystonia is acquired through either injury or genetic mutations, with poorly understood molecular and cellular mechanisms. Eukaryotic initiation factor alpha (eIF2α) controls cell state including neuronal plasticity via protein translation control and expression of ATF4. Dysregulated eIF2α phosphorylation (eIF2α-P) occurs in dystonia patients and models including DYT1, but the consequences are unknown. We increased/decreased eIF2α-P and tested motor control and neuronal properties in a Drosophila model. Bidirectionally altering eIF2α-P produced dystonia-like abnormal posturing and dyskinetic movements in flies. These movements were also observed with expression of the DYT1 risk allele. We identified cholinergic and D2-receptor neuroanatomical origins of these dyskinetic movements caused by genetic manipulations to dystonia molecular candidates eIF2α-P, ATF4, or DYT1, with evidence for decreased cholinergic release. In vivo, increased and decreased eIF2α-P increase synaptic connectivity at the NMJ with increased terminal size and bouton synaptic release sites. Long-term treatment of elevated eIF2α-P with ISRIB restored adult longevity, but not performance in a motor assay. Disrupted eIF2α-P signaling may alter neuronal connectivity, change synaptic release, and drive motor circuit changes in dystonia.

Insights into Calpain Activation and Rho-ROCK Signaling in Parkinson's Disease and Aging

Parkinson's disease (PD), a progressive neurodegenerative disease, has no cure, and current therapies are not effective at halting disease progression. The disease affects mid-brain dopaminergic neurons and, subsequently, the spinal cord, contributing to many debilitating symptoms associated with PD. The GTP-binding protein, Rho, plays a significant role in the cellular pathology of PD. The downstream effector of Rho, Rho-associated kinase (ROCK), plays multiple functions, including microglial activation and induction of inflammatory responses. Activated microglia have been implicated in the pathology of many neurodegenerative diseases, including PD, that initiate inflammatory responses, leading to neuron death. Calpain expression and activity is increased following glial activation, which triggers the Rho-ROCK pathway and induces inflammatory T cell activation and migration as well as mediates toxic α-synuclein (α-syn) aggregation and neuron death, indicating a pivotal role for calpain in the inflammatory and degenerative processes in PD. Increased calpain activity and Rho-ROCK activation may represent a new mechanism for increased oxidative damage in aging. This review will summarize calpain activation and the role of the Rho-ROCK pathway in oxidative stress and α-syn aggregation, their influence on the neurodegenerative process in PD and aging, and possible strategies and research directions for therapeutic intervention.

Updating functional brain units: Insights far beyond Luria

This paper reviews Luria's model of the three functional units of the brain. To meet this objective, several issues were reviewed: the theory of functional systems and the contributions of phylogenesis and embryogenesis to the brain's functional organization. This review revealed several facts. In the first place, the relationship/integration of basic homeostatic needs with complex forms of behavior. Secondly, the multi-scale hierarchical and distributed organization of the brain and interactions between cells and systems. Thirdly, the phylogenetic role of exaptation, especially in basal ganglia and cerebellum expansion. Finally, the tripartite embryogenetic organization of the brain: rhinic, limbic/paralimbic, and supralimbic zones. Obviously, these principles of brain organization are in contradiction with attempts to establish separate functional brain units. The proposed new model is made up of two large integrated complexes: a primordial-limbic complex (Luria's Unit I) and a telencephalic-cortical complex (Luria's Units II and III). As a result, five functional units were delineated: Unit I. Primordial or preferential (brainstem), for life-support, behavioral modulation, and waking regulation; Unit II. Limbic and paralimbic systems, for emotions and hedonic evaluation (danger and relevance detection and contribution to reward/motivational processing) and the creation of cognitive maps (contextual memory, navigation, and generativity [imagination]); Unit III. Telencephalic-cortical, for sensorimotor and cognitive processing (gnosis, praxis, language, calculation, etc.), semantic and episodic (contextual) memory processing, and multimodal conscious agency; Unit IV. Basal ganglia systems, for behavior selection and reinforcement (reward-oriented behavior); Unit V. Cerebellar systems, for the prediction/anticipation (orthometric supervision) of the outcome of an action. The proposed brain units are nothing more than abstractions within the brain's simultaneous and distributed physiological processes. As function transcends anatomy, the model necessarily involves transition and overlap between structures. Beyond the classic approaches, this review includes information on recent systemic perspectives on functional brain organization. The limitations of this review are discussed.

Tyrosine Hydroxylase Inhibitors and Dopamine Receptor Agonists Combination Therapy for Parkinson's Disease

There are currently no disease-modifying therapies for Parkinson's disease (PD), a progressive neurodegenerative disorder associated with dopaminergic neuronal loss. There is increasing evidence that endogenous dopamine (DA) can be a pathological factor in neurodegeneration in PD. Tyrosine hydroxylase (TH) is the key rate-limiting enzyme for DA generation. Drugs that inhibit TH, such as alpha-methyltyrosine (α-MT), have recently been shown to protect against neurodegeneration in various PD models. DA receptor agonists can activate post-synaptic DA receptors to alleviate DA-deficiency-induced PD symptoms. However, DA receptor agonists have no therapeutic effects against neurodegeneration. Thus, a combination therapy with DA receptor agonists plus TH inhibitors may be an attractive therapeutic approach. TH inhibitors can protect and promote the survival of remaining dopaminergic neurons in PD patients' brains, whereas DA receptor agonists activate post-synaptic DA receptors to alleviate PD symptoms. Additionally, other PD drugs, such as N-acetylcysteine (NAC) and anticholinergic drugs, may be used as adjunctive medications to improve therapeutic effects. This multi-drug cocktail may represent a novel strategy to protect against progressive dopaminergic neurodegeneration and alleviate PD disease progression.

Unraveling the role of Slc10a4 in auditory processing and sensory motor gating: Implications for neuropsychiatric disorders?

BACKGROUND

Psychiatric disorders, such as schizophrenia, are complex and challenging to study, partly due to the lack of suitable animal models. However, the absence of the Slc10a4 gene, which codes for a monoaminergic and cholinergic associated vesicular transporter protein, in knockout mice (Slc10a4-/-), leads to the accumulation of extracellular dopamine. A major challenge for studying schizophrenia is the lack of suitable animal models that accurately represent the disorder. We sought to overcome this challenge by using Slc10a4-/- mice as a potential model, considering their altered dopamine levels. This makes them a potential animal model for schizophrenia, a disorder known to be associated with altered dopamine signaling in the brain.

METHODS

The locomotion, auditory sensory filtering and prepulse inhibition (PPI) of Slc10a4-/- mice were quantified and compared to wildtype (WT) littermates. Intrahippocampal electrodes were used to record auditory event-related potentials (aERPs) for quantifying sensory filtering in response to paired-clicks. The channel above aERPs phase reversal was chosen for reliably comparing results between animals, and aERPs amplitude and latency of click responses were quantified. WT and Slc10a4-/- mice were also administered subanesthetic doses of ketamine to provoke psychomimetic behavior.

RESULTS

Baseline locomotion during auditory stimulation was similar between Slc10a4-/- mice and WT littermates. In WT animals, normal auditory processing was observed after i.p saline injections, and it was maintained under the influence of 5 mg/kg ketamine, but disrupted by 20 mg/kg ketamine. On the other hand, Slc10a4-/- mice did not show significant differences between N40 S1 and S2 amplitude responses in saline or low dose ketamine treatment. Auditory gating was considered preserved since the second N40 peak was consistently suppressed, but with increased latency. The P80 component showed higher amplitude, with shorter S2 latency under saline and 5 mg/kg ketamine treatment in Slc10a4-/- mice, which was not observed in WT littermates. Prepulse inhibition was also decreased in Slc10a4-/- mice when the longer interstimulus interval of 100 ms was applied, compared to WT littermates.

CONCLUSION

The Slc10a4-/- mice responses indicate that cholinergic and monoaminergic systems participate in the PPI magnitude, in the temporal coding (response latency) of the auditory sensory gating component N40, and in the amplitude of aERPs P80 component. These results suggest that Slc10a4-/- mice can be considered as potential models for neuropsychiatric conditions.

Treatment of Apathy in Parkinson's Disease and Implications for Underlying Pathophysiology

Apathy is a prevalent and highly debilitating non-motor symptom of Parkinson's disease (PD) that is often overlooked in clinical practice due to its subtle nature. This review aims to provide a comprehensive overview of the current evidence for the treatment of apathy in PD, highlighting recent advancements and emerging therapeutic avenues. In this review, we analyse a diverse array of treatment strategies for apathy in PD, including pharmacological interventions, non-pharmacological approaches, and emerging neuromodulation techniques. We evaluate the efficacy, safety, and limitations of established pharmacotherapies, such as dopaminergic agents, antidepressants, and cognitive enhancers. Additionally, we examine the promising role of non-pharmacological interventions, encompassing psychotherapies and behavioural interventions, in ameliorating apathetic symptoms. Furthermore, this review explores the effects of neuromodulation techniques on apathy, including the modulation of apathy via deep brain stimulation and emerging data on the potential influence of transcranial magnetic stimulation (TMS) on apathy in PD. Ultimately, a deeper understanding of effective treatment strategies for apathy has the potential to significantly improve the quality of life and overall well-being of individuals living with PD.

An Evidence-Based Update on Anticholinergic Use for Drug-Induced Movement Disorders

Drug-induced movement disorders (DIMDs) are associated with use of dopamine receptor blocking agents (DRBAs), including antipsychotics. The most common forms are drug-induced parkinsonism (DIP), dystonia, akathisia, and tardive dyskinesia (TD). Although rare, neuroleptic malignant syndrome (NMS) is a potentially life-threatening consequence of DRBA exposure. Recommendations for anticholinergic use in patients with DIMDs were developed on the basis of a roundtable discussion with healthcare professionals with extensive expertise in DIMD management, along with a comprehensive literature review. The roundtable agreed that "extrapyramidal symptoms" is a non-specific term that encompasses a range of abnormal movements. As such, it contributes to a misconception that all DIMDs can be treated in the same way, potentially leading to the misuse and overprescribing of anticholinergics. DIMDs are neurobiologically and clinically distinct, with different treatment paradigms and varying levels of evidence for anticholinergic use. Whereas evidence indicates anticholinergics can be effective for DIP and dystonia, they are not recommended for TD, akathisia, or NMS; nor are they supported for preventing DIMDs except in individuals at high risk for acute dystonia. Anticholinergics may induce serious peripheral adverse effects (e.g., urinary retention) and central effects (e.g., impaired cognition), all of which can be highly concerning especially in older adults. Appropriate use of anticholinergics therefore requires careful consideration of the evidence for efficacy (e.g., supportive for DIP but not TD) and the risks for serious adverse events. If used, anticholinergic medications should be prescribed at the lowest effective dose and for limited periods of time. When discontinued, they should be tapered gradually.

Sunset Yellow induced biochemical and histopathological alterations in rat brain sub-regions

Sunset Yellow, a synthetic orange azo food dye was examined in this study for its impact on the Wistar rat brain sub-regions. The dye was administered orally to weanling rats at the Acceptable Daily Intake level (4 mg/kg/bw) for 40 days, and brain sub-regions viz., frontal cortex, cerebellum and hippocampus were examined for biochemical and histopathological changes. The results showed a significant decrease in tissue protein levels, superoxide dismutase, and catalase activity, as well as a significant increase in lipid peroxide levels in all brain sub-regions. Glutathione-S-transferase and Glutathione Reductase activities decreased, while Glutathione peroxidase activity increased. The biogenic amine levels and Acetylcholinesterase activity were also altered, with the frontal cortex and hippocampus being the most affected. Additionally, the dye caused histopathological damage in all brain sub-regions examined. This study indicates that the ADI level of Sunset Yellow may adversely affect brain tissue by causing oxidative damage.

Impaired cerebral microvascular endothelial cells integrity due to elevated dopamine in myasthenic model

Myasthenia gravis is an autoimmune disease characterized by pathogenic antibodies that target structures of the neuromuscular junction. However, some patients also experience autonomic dysfunction, anxiety, depression, and other neurological symptoms, suggesting the complex nature of the neurological manifestations. With the aim of explaining the symptoms related to the central nervous system, we utilized a rat model to investigate the impact of dopamine signaling in the central nervous and peripheral circulation. We adopted several screening methods, including western blot, quantitative PCR, mass spectrum technique, immunohistochemistry, immunofluorescence staining, and flow cytometry. In this study, we observed increased and activated dopamine signaling in both the central nervous system and peripheral circulation of myasthenia gravis rats. Furthermore, changes in the expression of two key molecules, Claudin5 and CD31, in endothelial cells of the blood-brain barrier were also examined in these rats. We also confirmed that dopamine incubation reduced the expression of ZO1, Claudin5, and CD31 in endothelial cells by inhibiting the Wnt/β-catenin signaling pathway. Overall, this study provides novel evidence suggesting that pathologically elevated dopamine in both the central nervous and peripheral circulation of myasthenia gravis rats impair brain-blood barrier integrity by inhibiting junction protein expression in brain microvascular endothelial cells through the Wnt/β-catenin pathway.

Interplay of G-proteins and Serotonin in the Neuroimmunoinflammatory Model of Chronic Stress and Depression: A Narrative Review

INTRODUCTION

This narrative review addresses the clinical challenges in stress-related disorders such as depression, focusing on the interplay between neuron-specific and pro-inflammatory mechanisms at the cellular, cerebral, and systemic levels.

OBJECTIVE

We aim to elucidate the molecular mechanisms linking chronic psychological stress with low-grade neuroinflammation in key brain regions, particularly focusing on the roles of G proteins and serotonin (5-HT) receptors.

METHODS

This comprehensive review of the literature employs systematic, narrative, and scoping review methodologies, combined with systemic approaches to general pathology. It synthesizes current research on shared signaling pathways involved in stress responses and neuroinflammation, including calcium-dependent mechanisms, mitogen-activated protein kinases, and key transcription factors like NF-κB and p53. The review also focuses on the role of G protein-coupled neurotransmitter receptors (GPCRs) in immune and pro-inflammatory responses, with a detailed analysis of how 13 of 14 types of human 5-HT receptors contribute to depression and neuroinflammation.

RESULTS

The review reveals a complex interaction between neurotransmitter signals and immunoinflammatory responses in stress-related pathologies. It highlights the role of GPCRs and canonical inflammatory mediators in influencing both pathological and physiological processes in nervous tissue.

CONCLUSION

The proposed Neuroimmunoinflammatory Stress Model (NIIS Model) suggests that proinflammatory signaling pathways, mediated by metabotropic and ionotropic neurotransmitter receptors, are crucial for maintaining neuronal homeostasis. Chronic mental stress can disrupt this balance, leading to increased pro-inflammatory states in the brain and contributing to neuropsychiatric and psychosomatic disorders, including depression. This model integrates traditional theories on depression pathogenesis, offering a comprehensive understanding of the multifaceted nature of the condition.

Transcranial photobiomodulation ameliorates midbrain and striatum neurochemical impairments and behavioral deficits in reserpine-induced parkinsonism in rats

Photobiomodulation (PBM) of deep brain structures through transcranial infrared irradiation might be an effective treatment for Parkinson's disease (PD). However, the mechanisms underlying this intervention should be elucidated to optimize the therapeutic outcome and maximize therapeutic efficacy. The present study aimed at investigating the oxidative stress-related parameters of malondialdehyde (MDA), nitric oxide (NO), and reduced glutathione (GSH) and the enzymatic activities of sodium-potassium-ATPase (Na+, K+-ATPase), Acetylcholinesterase (AChE), and monoamine oxidase (MAO) and monoamine levels (dopamine (DA), norepinephrine (NE) and serotonin (5-HT) in the midbrain and striatum of reserpine-induced PD in an animal model treated with PBM. Furthermore, the locomotor behavior of the animals has been determined by the open field test. Animals were divided into three groups; the control group, the PD-induced model group, and the PD-induced model treated with the PBM group. Non-invasive treatment of animals for 14 days with 100 mW, 830 nm laser has demonstrated successful attainment in the recovery of oxidative stress, and enzymatic activities impairments induced by reserpine (0.2 mg/kg) in both midbrain and striatum of adult male Wistar rats. PBM also improved the decrease in DA, NE, and 5-HT in the investigated brain regions. On a behavioral level, animals showed improvement in their locomotion activity. These findings have shed more light on some mechanisms underlying the treatment potential of PBM and displayed the safety, easiness, and efficacy of PBM treatment as an alternative to pharmacological treatment for PD.

Repeated Intravenous Administration of Human Neural Stem Cells Producing Choline Acetyltransferase Exerts Anti-Aging Effects in Male F344 Rats

Major features of aging might be progressive decreases in cognitive function and physical activity, in addition to withered appearance. Previously, we reported that the intracerebroventricular injection of human neural stem cells (NSCs named F3) encoded the choline acetyltransferase gene (F3.ChAT). The cells secreted acetylcholine and growth factors (GFs) and neurotrophic factors (NFs), thereby improving learning and memory function as well as the physical activity of aged animals. In this study, F344 rats (10 months old) were intravenously transplanted with F3 or F3.ChAT NSCs (1 × 106 cells) once a month to the 21st month of age. Their physical activity and cognitive function were investigated, and brain acetylcholine (ACh) and cholinergic and dopaminergic system markers were analyzed. Neuroprotective and neuroregenerative activities of stem cells were also confirmed by analyzing oxidative damages, neuronal skeletal protein, angiogenesis, brain and muscle weights, and proliferating host stem cells. Stem cells markedly improved both cognitive and physical functions, in parallel with the elevation in ACh levels in cerebrospinal fluid and muscles, in which F3.ChAT cells were more effective than F3 parental cells. Stem cell transplantation downregulated CCL11 and recovered GFs and NFs in the brain, leading to restoration of microtubule-associated protein 2 as well as functional markers of cholinergic and dopaminergic systems, along with neovascularization. Stem cells also restored muscular GFs and NFs, resulting in increased angiogenesis and muscle mass. In addition, stem cells enhanced antioxidative capacity, attenuating oxidative damage to the brain and muscles. The results indicate that NSCs encoding ChAT improve cognitive function and physical activity of aging animals by protecting and recovering functions of multiple organs, including cholinergic and dopaminergic systems, as well as muscles from oxidative injuries through secretion of ACh and GFs/NFs, increased antioxidant elements, and enhanced blood flow.

Omega 3 fatty acid improves sexual and erectile function in BPF-treated rats by upregulating NO/cGMP signaling and steroidogenic enzymes activities

Bisphenol F (BPF) is an environmental pollutant that has been implicated in sexual dysfunction. Omega 3 fatty acid (O3FA), on the other hand, is an antioxidant with the ability to improve fertility indices. However, no study has explored the possible ameliorative effect of O3FA on BPF-induced sexual dysfunction. Thus, the effect of BPF and/or O3FA on male sexual performance was investigated. Male Wistar rats were randomized into 6 groups, corn oil-treated, O3FA low and high dose (100 and 300 mg/kg), BPF-treated, BPF + O3FA low and BPF + O3FA high dose. BPF significantly impaired male sexual competence, evidenced by a reduction in motivation to mate, prolonged mount, intromission and ejaculation latency, and post-ejaculatory index. Furthermore, a reduction in mount, intromission, and ejaculation frequency were observed. Also, BPF caused a decrease in gonadotropin releasing hormone, follicle stimulating hormone, luteinizing hormone, testosterone, nitric oxide (NO) cyclic guanosine monophosphate (cGMP), 3beta-hydroxysteroid dehydrogenase (3β-HSD), 17beta-hydroxysteroid dehydrogenase (17β-HSD), dopamine, and acetylcholine esterase. Furthermore, it was accompanied by a significant increase in prolactin and estrogen and poor pregnancy outcomes. These observed BPF-led alterations were abolished by O3FA administration. This study showed that O3FA ameliorates BPF-induced sexual dysfunction by upregulating NO/cGMP signaling and steroidogenic enzymes activities.

Deep brain stimulation alleviates tics in Tourette syndrome via striatal dopamine transmission

Tourette syndrome is a childhood-onset neuropsychiatric disorder characterized by intrusive motor and vocal tics that can lead to self-injury and deleterious mental health complications. While dysfunction in striatal dopamine neurotransmission has been proposed to underlie tic behaviour, evidence is scarce and inconclusive. Deep brain stimulation (DBS) of the thalamic centromedian parafascicular complex (CMPf), an approved surgical interventive treatment for medical refractory Tourette syndrome, may reduce tics by affecting striatal dopamine release. Here, we use electrophysiology, electrochemistry, optogenetics, pharmacological treatments and behavioural measurements to mechanistically examine how thalamic DBS modulates synaptic and tonic dopamine activity in the dorsomedial striatum. Previous studies demonstrated focal disruption of GABAergic transmission in the dorsolateral striatum of rats led to repetitive motor tics recapitulating the major symptom of Tourette syndrome. We employed this model under light anaesthesia and found CMPf DBS evoked synaptic dopamine release and elevated tonic dopamine levels via striatal cholinergic interneurons while concomitantly reducing motor tic behaviour. The improvement in tic behaviour was found to be mediated by D2 receptor activation as blocking this receptor prevented the therapeutic response. Our results demonstrate that release of striatal dopamine mediates the therapeutic effects of CMPf DBS and points to striatal dopamine dysfunction as a driver for motor tics in the pathoneurophysiology of Tourette syndrome.

Patient-specific models link neurotransmitter receptor mechanisms with motor and visuospatial axes of Parkinson's disease

Parkinson's disease involves multiple neurotransmitter systems beyond the classical dopaminergic circuit, but their influence on structural and functional alterations is not well understood. Here, we use patient-specific causal brain modeling to identify latent neurotransmitter receptor-mediated mechanisms contributing to Parkinson's disease progression. Combining the spatial distribution of 15 receptors from post-mortem autoradiography with 6 neuroimaging-derived pathological factors, we detect a diverse set of receptors influencing gray matter atrophy, functional activity dysregulation, microstructural degeneration, and dendrite and dopaminergic transporter loss. Inter-individual variability in receptor mechanisms correlates with symptom severity along two distinct axes, representing motor and psychomotor symptoms with large GABAergic and glutamatergic contributions, and cholinergically-dominant visuospatial, psychiatric and memory dysfunction. Our work demonstrates that receptor architecture helps explain multi-factorial brain re-organization, and suggests that distinct, co-existing receptor-mediated processes underlie Parkinson's disease.

Advances in targeting neurotransmitter systems in dystonia

Dystonia is characterised as uncontrolled, often painful involuntary muscle contractions that cause abnormal postures and repetitive or twisting movements. These movements can be continuous or sporadic and affect different parts of the body and range in severity. Dystonia and its related conditions present a huge cause of neurological morbidity worldwide. Although therapies are available, achieving optimal symptom control without major unwanted effects remains a challenge. Most pharmacological treatments for dystonia aim to modulate the effects of one or more neurotransmitters in the central nervous system, but doing so effectively and with precision is far from straightforward. In this chapter we discuss the physiology of key neurotransmitters, including dopamine, noradrenaline, serotonin (5-hydroxytryptamine), acetylcholine, GABA, glutamate, adenosine and cannabinoids, and their role in dystonia. We explore the ways in which existing pharmaceuticals as well as novel agents, currently in clinical trial or preclinical development, target dystonia, and their respective advantages and disadvantages. Finally, we discuss current and emerging genetic therapies which may be used to treat genetic forms of dystonia.

Oxycodone-induced dopaminergic and respiratory effects are modulated by deep brain stimulation

Introduction: Opioids are the leading cause of overdose death in the United States, accounting for almost 70,000 deaths in 2020. Deep brain stimulation (DBS) is a promising new treatment for substance use disorders. Here, we hypothesized that VTA DBS would modulate both the dopaminergic and respiratory effect of oxycodone. Methods: Multiple-cyclic square wave voltammetry (M-CSWV) was used to investigate how deep brain stimulation (130 Hz, 0.2 ms, and 0.2 mA) of the rodent ventral segmental area (VTA), which contains abundant dopaminergic neurons, modulates the acute effects of oxycodone administration (2.5 mg/kg, i.v.) on nucleus accumbens core (NAcc) tonic extracellular dopamine levels and respiratory rate in urethane-anesthetized rats (1.5 g/kg, i.p.). Results: I.V. administration of oxycodone resulted in an increase in NAcc tonic dopamine levels (296.9 ± 37.0 nM) compared to baseline (150.7 ± 15.5 nM) and saline administration (152.0 ± 16.1 nM) (296.9 ± 37.0 vs. 150.7 ± 15.5 vs. 152.0 ± 16.1, respectively, p = 0.022, n = 5). This robust oxycodone-induced increase in NAcc dopamine concentration was associated with a sharp reduction in respiratory rate (111.7 ± 2.6 min-1 vs. 67.9 ± 8.3 min-1; pre- vs. post-oxycodone; p < 0.001). Continuous DBS targeted at the VTA (n = 5) reduced baseline dopamine levels, attenuated the oxycodone-induced increase in dopamine levels to (+39.0% vs. +95%), and respiratory depression (121.5 ± 6.7 min-1 vs. 105.2 ± 4.1 min-1; pre- vs. post-oxycodone; p = 0.072). Discussion: Here we demonstrated VTA DBS alleviates oxycodone-induced increases in NAcc dopamine levels and reverses respiratory suppression. These results support the possibility of using neuromodulation technology for treatment of drug addiction.

FAST (Flexible Acetylcholine Sensing Thread): Real-Time Detection of Acetylcholine with a Flexible Solid-Contact Potentiometric Sensor

Acetylcholine (ACh) is involved in memory and learning and has implications in neurodegenerative diseases; it is therefore important to study the dynamics of ACh in the brain. This work creates a flexible solid-contact potentiometric sensor for in vitro and in vivo recording of ACh in the brain and tissue homogenate. We fabricate this sensor using a 250 μm diameter cotton yarn coated with a flexible conductive ink and an ACh sensing membrane that contains a calix[4]arene ionophore. The exposed ion-to-electron transducer was sealed with a 2.5 μm thick Parylene C coating to maintain the flexibility of the sensor. The resulting diameter of the flexible ACh sensing thread (FAST) was 400 μm. The FAST showed a linear response range from 1.0 μM to 10.0 mM in deionized water, with a near-Nernstian slope of 56.11 mV/decade and a limit of detection of 2.6 μM. In artificial cerebrospinal fluid, the limit of detection increased to 20 μM due to the background signal of ionic content of the cerebrospinal fluid. The FAST showed a signal stability of 226 μV/h over 24 h. We show that FAST can measure ACh dynamics in sheep brain tissue and sheep brain homogenate after ACh spiking. FAST is the first flexible electrochemical sensor for monitoring ACh dynamics in the brain.

High frequency deep brain stimulation can mitigate the acute effects of cocaine administration on tonic dopamine levels in the rat nucleus accumbens

Cocaine's addictive properties stem from its capacity to increase tonic extracellular dopamine levels in the nucleus accumbens (NAc). The ventral tegmental area (VTA) is a principal source of NAc dopamine. To investigate how high frequency stimulation (HFS) of the rodent VTA or nucleus accumbens core (NAcc) modulates the acute effects of cocaine administration on NAcc tonic dopamine levels multiple-cyclic square wave voltammetry (M-CSWV) was used. VTA HFS alone decreased NAcc tonic dopamine levels by 42%. NAcc HFS alone resulted in an initial decrease in tonic dopamine levels followed by a return to baseline. VTA or NAcc HFS following cocaine administration prevented the cocaine-induced increase in NAcc tonic dopamine. The present results suggest a possible underlying mechanism of NAc deep brain stimulation (DBS) in the treatment of substance use disorders (SUDs) and the possibility of treating SUD by abolishing dopamine release elicited by cocaine and other drugs of abuse by DBS in VTA, although further studies with chronic addiction models are required to confirm that. Furthermore, we demonstrated the use of M-CSWV can reliably measure tonic dopamine levels in vivo with both drug administration and DBS with minimal artifacts.

Applications of Induced Pluripotent Stem Cell-Derived Glia in Brain Disease Research and Treatment

Glia are integral components of neural networks and are crucial in both physiological functions and pathological processes of the brain. Many brain diseases involve glial abnormalities, including inflammatory changes, mitochondrial damage, calcium signaling disturbance, hemichannel opening, and loss of glutamate transporters. Induced pluripotent stem cell (iPSC)-derived glia provide opportunities to study the contributions of glia in human brain diseases. These cells have been used for human disease modeling as well as generating new therapies. This chapter introduces glial involvement in brain diseases, then summarizes different methods of generating iPSC-derived glia disease models of these cells. Finally, strategies for treating disease using iPSC-derived glia are discussed. The goal of this chapter is to provide an overview and shed light on the applications of iPSC-derived glia in brain disease research and treatment.

Drug repurposing: Clemastine fumarate and neurodegeneration

Neurodegenerative diseases have been a weighty problem in elder people who might be stricken with motor or/and cognition defects with lower life quality urging for effective treatment. Drugs are costly from development to market, so that drug repurposing, exploration of existing drugs for novel therapeutic purposes, becomes a wise and popular strategy to raise new treatment options. Clemastine fumarate, different from anti-allergic effect as H1 histamine antagonist, was screened and identified as promising drug for remyelination and autophagy enhancement. Surprisingly, fumarate salt also has similar effect. Hence, whether clemastine fumarate would make a protective impact on neurodegenerative diseases and what contribution fumarate probably makes are intriguing to us. In this review, we summarize the potential mechanism surrounding clemastine fumarate in current literature, and try to distinguish independent or synergistic effect between clemastine and fumarate, aiming to find worthwhile research direction for neurodegeneration diseases.

Relapse of first-episode schizophrenia patients and neurocognitive impairment: The role of dopaminergic and anticholinergic burden

BACKGROUND

The prevention of relapse may be a key factor to diminish the cognitive impairment of first-episode schizophrenia (FES) patients. We aimed to ascertain the effects of relapse, and dopaminergic and anticholinergic treatment burdens on cognitive functioning in the follow-up.

METHODS

Ninety-nine FES patients participated in this study. Cognitive assessments were performed at baseline and after 3 years of follow-up or, in those patients who relapsed, after &gt;2 months of stabilization of the new acute psychotic episode. The primary outcomes were final cognitive dimensions.

RESULTS

Repeated measures MANOVA analyses showed improvements in the whole sample on the end-point assessments in processing speed and social cognition. However, only impairment in social cognition showed a significant interaction with relapse by time in this sample. Relapse in FES patients was significantly associated with poor performance on end-point assessments of working memory, social cognition and global cognitive score. Anticholinergic burden, but not dopaminergic burden, was associated with verbal memory impairment. These significant associations resulted after controlling for baseline cognitive functioning, relapse and dopaminergic burden.

CONCLUSIONS

The relationship between relapse and cognitive impairment in recovered FES patients seems to be particularly complex at the short-term follow-up of these patients. While relapse was associated with working memory, social cognition impairments and global cognitive score, anticholinergic burden might play an additional worsening effect on verbal memory. Thus, tailoring or changing antipsychotics and other drugs to reduce their anticholinergic burden may be a potential modifiable factor to diminish cognitive impairment at this stage of the illness.

Age-dependent effects of social isolation on mesolimbic dopamine release

In humans, social isolation is a known risk factor for disorders such as substance use disorder and depression. In rodents, social isolation is a commonly used environmental manipulation that increases the occurrence of behaviors related to these disorders. Age is thought to influence the effects of social isolation, but this predictive relationship is not well-understood. The present study aimed to determine the effects of social isolation on mesolimbic dopamine release at different developmental age points in mice. The experimental ages and their corresponding comparison to human age stages are as follows: 1 month = adolescence, 4 months = mature adulthood, 12 months = middle adulthood, and 18 months = older adult. Mice were socially isolated for 6 weeks during these developmental stages, then in vivo fixed potential amperometry with recording electrodes in the nucleus accumbens was used to measure stimulation-evoked dopamine release, the synaptic half-life of dopamine, dopamine autoreceptor functioning, and the dopaminergic response to cocaine. Isolation altered dopamine functioning in an age-dependent manner. Specifically, isolation increased dopamine release in the adult ages, but not adolescence, potentially due to increased inhibitory effects of dopamine autoreceptors following adolescent social isolation. Regarding the cocaine challenge, isolation increased dopaminergic responses to cocaine in adolescent mice, but not the adult mice. These findings have implications for clinical and experimental settings. Elucidating the relationship between age, social isolation, and neurochemical changes associated with substance use disorder and depression may lead to improvements in preventing and treating these disorders.

A review on pathology, mechanism, and therapy for cerebellum and tremor in Parkinson's disease

Tremor is one of the core symptoms of Parkinson’s disease (PD), but its mechanism is poorly understood. The cerebellum is a growing focus in PD-related researches and is reported to play an important role in tremor in PD. The cerebellum may participate in the modulation of tremor amplitude via cerebello-thalamo-cortical circuits. The cerebellar excitatory projections to the ventral intermediate nucleus of the thalamus may be enhanced due to PD-related changes, including dopaminergic/non-dopaminergic system abnormality, white matter damage, and deep nuclei impairment, which may contribute to dysregulation and resistance to levodopa of tremor. This review summarized the pathological, structural, and functional changes of the cerebellum in PD and discussed the role of the cerebellum in PD-related tremor, aiming to provide an overview of the cerebellum-related mechanism of tremor in PD.

Biological Potential, Gastrointestinal Digestion, Absorption, and Bioavailability of Algae-Derived Compounds with Neuroprotective Activity: A Comprehensive Review

Currently, there is no known cure for neurodegenerative disease. However, the available therapies aim to manage some of the symptoms of the disease. Human neurodegenerative diseases are a heterogeneous group of illnesses characterized by progressive loss of neuronal cells and nervous system dysfunction related to several mechanisms such as protein aggregation, neuroinflammation, oxidative stress, and neurotransmission dysfunction. Neuroprotective compounds are essential in the prevention and management of neurodegenerative diseases. This review will focus on the neurodegeneration mechanisms and the compounds (proteins, polyunsaturated fatty acids (PUFAs), polysaccharides, carotenoids, phycobiliproteins, phenolic compounds, among others) present in seaweeds that have shown in vivo and in vitro neuroprotective activity. Additionally, it will cover the recent findings on the neuroprotective effects of bioactive compounds from macroalgae, with a focus on their biological potential and possible mechanism of action, including microbiota modulation. Furthermore, gastrointestinal digestion, absorption, and bioavailability will be discussed. Moreover, the clinical trials using seaweed-based drugs or extracts to treat neurodegenerative disorders will be presented, showing the real potential and limitations that a specific metabolite or extract may have as a new therapeutic agent considering the recent approval of a seaweed-based drug to treat Alzheimer’s disease.

The Mesoscopic Connectome of the Cholinergic Pontomesencephalic Tegmentum

The pontomesencephalic tegmentum, comprising the pedunculopontine nucleus and laterodorsal tegmental nucleus, is involved in various functions via complex connections; however, the organizational structure of these circuits in the whole brain is not entirely clear. Here, combining viral tracing with fluorescent micro-optical sectional tomography, we comprehensively investigated the input and output circuits of two cholinergic subregions in a continuous whole-brain dataset. We found that these nuclei receive abundant input with similar spatial distributions but with different quantitative measures and acquire similar neuromodulatory afferents from the ascending reticular activation system. Meanwhile, these cholinergic nuclei project to similar targeting areas throughout multiple brain regions and have different spatial preferences in 3D. Moreover, some cholinergic connections are unidirectional, including projections from the pedunculopontine nucleus and laterodorsal tegmental nucleus to the ventral posterior complex of the thalamus, and have different impacts on locomotion and anxiety. These results reveal the integrated cholinergic connectome of the midbrain, thus improving the present understanding of the organizational structure of the pontine-tegmental cholinergic system from its anatomical structure to its functional modulation.

Similarities and differences between nigral and enteric dopaminergic neurons unravel distinctive involvement in Parkinson's disease

In addition to the well-known degeneration of midbrain dopaminergic neurons, enteric neurons can also be affected in neurodegenerative disorders such as Parkinson's disease (PD). Dopaminergic neurons have recently been identified in the enteric nervous system (ENS). While ENS dopaminergic neurons have been shown to degenerate in genetic mouse models of PD, analyses of their survival in enteric biopsies of PD patients have provided inconsistent results to date. In this context, this review seeks to highlight the distinctive and shared factors and properties that control the evolution of these two sets of dopaminergic neurons from neuronal precursors to aging neurons. Although their cellular sources and developmental times of origin differ, midbrain and ENS dopaminergic neurons express many transcription factors in common and their respective environments express similar neurotrophic molecules. For example, Foxa2 and Sox6 are expressed by both populations to promote the specification, differentiation, and long-term maintenance of the dopaminergic phenotype. Both populations exhibit sustained patterns of excitability that drive intrinsic vulnerability over time. In disorders such as PD, colon biopsies have revealed aggregation of alpha-synuclein in the submucosal plexus where dopaminergic neurons reside and lack blood barrier protection. Thus, these enteric neurons may be more susceptible to neurotoxic insults and aggregation of α-synuclein that spreads from gut to midbrain. Under sustained stress, inefficient autophagy leads to neurodegeneration, GI motility dysfunction, and PD symptoms. Recent findings suggest that novel neurotrophic factors such as CDNF have the potential to be used as neuroprotective agents to prevent and treat ENS symptoms of PD.

From hallucinations to synaesthesia: A circular inference account of unimodal and multimodal erroneous percepts in clinical and drug-induced psychosis

Psychedelics distort perception and induce visual and multimodal hallucinations as well as synaesthesia. This is in contradiction with the high prevalence of distressing voices in schizophrenia. Here we introduce a unifying account of unimodal and multimodal erroneous percepts based on circular inference. We show that amplification of top-down predictions (descending loops) leads to an excessive reliance on priors and aberrant levels of integration of the sensory representations, resulting in crossmodal percepts and stronger illusions. By contrast, amplification of bottom-up information (ascending loops) results in overinterpretation of unreliable sensory inputs and high levels of segregation between sensory modalities, bringing about unimodal hallucinations and reduced vulnerability to illusions. We delineate a canonical microcircuit in which layer-specific inhibition controls the propagation of information across hierarchical levels: inhibitory interneurons in the deep layers exert control over priors, removing descending loops. Conversely, inhibition in the supragranular layers counterbalances the effects of the ascending loops. Overall, we put forward a multiscale and transnosographic account of erroneous percepts with important theoretical, conceptual and clinical implications.

Anodal Transcranial Direct Current Stimulation Could Modulate Cortical Excitability and the Central Cholinergic System in Akinetic Rigid-Type Parkinson's Disease: Pilot Study

Background

Transcranial direct current stimulation (tDCS) is a non-invasive technique that has been widely studied as an alternative treatment for Parkinson's disease (PD). However, its clinical benefit remains unclear. In this study, we aimed to investigate the effect of tDCS on the central cholinergic system and cortical excitability in mainly akinetic rigid-type patients with PD.

Methods

In total, 18 patients with PD were prospectively enrolled and underwent 5 sessions of anodal tDCS on the M1 area, which is on the contralateral side of the dominant hand. We excluded patients with PD who had evident resting tremor of the hand to reduce the artifact of electrophysiologic findings. We compared clinical scales reflecting motor, cognitive, and mood symptoms between pre- and post-tDCS. Additionally, we investigated the changes in electrophysiologic parameters, such as short latency afferent inhibition (SAI) (%), which reflects the central cholinergic system.

Results

The United Parkinson's Disease Rating Scale Part 3 (UPDRS-III), the Korean-Montreal Cognitive Assessment (MoCA-K), and Beck Depression Inventory (BDI) scores were significantly improved after anodal tDCS (p < 0.01, p < 0.01, and p < 0.01). Moreover, motor evoked potential amplitude ratio (MEPAR) (%) and integrated SAI showed significant improvement after tDCS (p < 0.01 and p < 0.01). The mean values of the change in integrated SAI (%) were significantly correlated with the changes in UPDRS-III scores; however, the MoCA-K and BDI scores did not show differences.

Conclusions

Anodal tDCS could influence the central cholinergic system, such as frontal cortical excitability and depression in PD. This mechanism could underlie the clinical benefit of tDCS in patients with PD.

Modeling and Targeting Neuroglial Interactions with Human Pluripotent Stem Cell Models

Generation of relevant and robust models for neurological disorders is of main importance for both target identification and drug discovery. The non-cell autonomous effects of glial cells on neurons have been described in a broad range of neurodegenerative and neurodevelopmental disorders, pointing to neuroglial interactions as novel alternative targets for therapeutics development. Interestingly, the recent breakthrough discovery of human induced pluripotent stem cells (hiPSCs) has opened a new road for studying neurological and neurodevelopmental disorders “in a dish”. Here, we provide an overview of the generation and modeling of both neuronal and glial cells from human iPSCs and a brief synthesis of recent work investigating neuroglial interactions using hiPSCs in a pathophysiological context.

Neuroprotective effects of curcumin on the cerebellum in a rotenone‐induced Parkinson’s Disease Model

Aims

Methods

Results

Conclusion

The PET tracer [11C]MK-6884 quantifies M4 muscarinic receptor in rhesus monkeys and patients with Alzheimer's disease

[Figure: see text].

Markers of muscarinic deficit for individualized treatment in schizophrenia

Recent clinical studies have shown that agonists at muscarinic acetylcholine receptors effectively reduce schizophrenia symptoms. It is thus conceivable that, for the first time, a second substance class of procholinergic antipsychotics could become established alongside the usual antidopaminergic antipsychotics. In addition, various basic science studies suggest that there may be a subgroup of schizophrenia in which hypofunction of muscarinic acetylcholine receptors is of etiological importance. This could represent a major opportunity for individualized treatment of schizophrenia if markers can be identified that predict response to procholinergic vs. antidopaminergic interventions. In this perspective, non-response to antidopaminergic antipsychotics, specific symptom patterns like visual hallucinations and strong disorganization, the presence of antimuscarinic antibodies, ERP markers such as mismatch negativity, and radiotracers are presented as possible in vivo markers of muscarinic deficit and thus potentially of response to procholinergic therapeutics. Finally, open questions and further research steps are outlined.

Amyloid Beta Dynamics in Biological Fluids-Therapeutic Impact

Despite the significant impact of Alzheimer's disease (AD) at individual and socioeconomic levels and the numerous research studies carried out on this topic over the last decades, the treatments available in daily clinical practice remain less than satisfactory. Among the accepted etiopathogenic hypotheses, the amyloidogenic pathway theory, although intensively studied and even sometimes controversial, is still providing relevant theoretical elements for understanding the etiology of AD and for the further development of possible therapeutic tools. In this sense, this review aims to offer new insights related to beta amyloid (Aβ), an essential biomarker in AD. First the structure and function of Aβ in normal and pathological conditions are presented in detail, followed by a discussion on the dynamics of Aβ at the level of different biological compartments. There is focus on Aβ elimination modalities at central nervous system (CNS) level, and clearance via the blood-brain barrier seems to play a crucial/dominant role. Finally, different theoretical and already-applied therapeutic approaches for CNS Aβ elimination are presented, including the recent "peripheral sink therapeutic strategy" and "cerebrospinal fluid sinks therapeutic strategy". These data outline the need for a multidisciplinary approach designed to deliver a solution to stimulate Aβ clearance in more direct ways, including from the cerebrospinal fluid level.

Corticostriatal Circuit Models of Cognitive Impairments Induced by Fetal Exposure to Alcohol

The term fetal alcohol spectrum disorder includes a group of diseases caused by fetal alcohol exposure (FAE). Patients with fetal alcohol spectrum disorder display heterogeneous socioemotional and cognitive deficits, particularly in the domain of executive function, that share symptoms with other neuropsychiatric disorders. Despite the availability of several preclinical models, the developmental brain defects causally linked to behavioral deficits induced by FAE remain poorly understood. Here, we first review the effects of FAE on corticostriatal development and its impact on both corticostriatal pathway function and cognitive abilities. We propose three non-mutually exclusive circuit models of corticostriatal dysfunctions to account for some of the FAE-induced cognitive deficits. One model posits that associative-sensorimotor imbalance causes hyper goal-directed behavior, and a second model implies that alteration of prefrontal-striatal behavioral suppression circuits results in loss of behavioral inhibition. A third model suggests that local striatal circuit deficits affect striatal neuronal ensemble function to impair action selection and performance. Finally, we discuss how preclinical approaches applied to these circuit models could offer potential rescue strategies for executive function deficits in patients with fetal alcohol spectrum disorder.

Neuromodulation of Hippocampal-Prefrontal Cortical Synaptic Plasticity and Functional Connectivity: Implications for Neuropsychiatric Disorders

The hippocampus-prefrontal cortex (HPC-PFC) pathway plays a fundamental role in executive and emotional functions. Neurophysiological studies have begun to unveil the dynamics of HPC-PFC interaction in both immediate demands and long-term adaptations. Disruptions in HPC-PFC functional connectivity can contribute to neuropsychiatric symptoms observed in mental illnesses and neurological conditions, such as schizophrenia, depression, anxiety disorders, and Alzheimer's disease. Given the role in functional and dysfunctional physiology, it is crucial to understand the mechanisms that modulate the dynamics of HPC-PFC communication. Two of the main mechanisms that regulate HPC-PFC interactions are synaptic plasticity and modulatory neurotransmission. Synaptic plasticity can be investigated inducing long-term potentiation or long-term depression, while spontaneous functional connectivity can be inferred by statistical dependencies between the local field potentials of both regions. In turn, several neurotransmitters, such as acetylcholine, dopamine, serotonin, noradrenaline, and endocannabinoids, can regulate the fine-tuning of HPC-PFC connectivity. Despite experimental evidence, the effects of neuromodulation on HPC-PFC neuronal dynamics from cellular to behavioral levels are not fully understood. The current literature lacks a review that focuses on the main neurotransmitter interactions with HPC-PFC activity. Here we reviewed studies showing the effects of the main neurotransmitter systems in long- and short-term HPC-PFC synaptic plasticity. We also looked for the neuromodulatory effects on HPC-PFC oscillatory coordination. Finally, we review the implications of HPC-PFC disruption in synaptic plasticity and functional connectivity on cognition and neuropsychiatric disorders. The comprehensive overview of these impairments could help better understand the role of neuromodulation in HPC-PFC communication and generate insights into the etiology and physiopathology of clinical conditions.

Cholinergic Receptor Modulation as a Target for Preventing Dementia in Parkinson's Disease

Parkinson’s disease (PD) is a neurodegenerative condition characterized by the loss of dopaminergic neurons in the substantia nigra pars compacta (SNpc) in the midbrain resulting in progressive impairment in cognitive and motor abilities. The physiological and molecular mechanisms triggering dopaminergic neuronal loss are not entirely defined. PD occurrence is associated with various genetic and environmental factors causing inflammation and mitochondrial dysfunction in the brain, leading to oxidative stress, proteinopathy, and reduced viability of dopaminergic neurons. Oxidative stress affects the conformation and function of ions, proteins, and lipids, provoking mitochondrial DNA (mtDNA) mutation and dysfunction. The disruption of protein homeostasis induces the aggregation of alpha-synuclein (α-SYN) and parkin and a deficit in proteasome degradation. Also, oxidative stress affects dopamine release by activating ATP-sensitive potassium channels. The cholinergic system is essential in modulating the striatal cells regulating cognitive and motor functions. Several muscarinic acetylcholine receptors (mAChR) and nicotinic acetylcholine receptors (nAChRs) are expressed in the striatum. The nAChRs signaling reduces neuroinflammation and facilitates neuronal survival, neurotransmitter release, and synaptic plasticity. Since there is a deficit in the nAChRs in PD, inhibiting nAChRs loss in the striatum may help prevent dopaminergic neurons loss in the striatum and its pathological consequences. The nAChRs can also stimulate other brain cells supporting cognitive and motor functions. This review discusses the cholinergic system as a therapeutic target of cotinine to prevent cognitive symptoms and transition to dementia in PD.

Increased Endogenous GDNF in Mice Protects Against Age-Related Decline in Neuronal Cholinergic Markers

Gradual decline in cholinergic transmission and cognitive function occurs during normal aging, whereas pathological loss of cholinergic function is a hallmark of different types of dementia, including Alzheimer’s disease (AD), Lewy body dementia (LBD), and Parkinson’s disease dementia (PDD). Glial cell line-derived neurotrophic factor (GDNF) is known to modulate and enhance the dopamine system. However, how endogenous GDNF influences brain cholinergic transmission has remained elusive. In this study, we explored the effect of a twofold increase in endogenous GDNF (Gdnf hypermorphic mice, Gdnf^wt/hyper) on cholinergic markers and cognitive function upon aging. We found that Gdnf^wt/hyper mice resisted an overall age-associated decline in the cholinergic index observed in the brain of Gdnf^wt/wt animals. Biochemical analysis revealed that the level of nerve growth factor (NGF), which is important for survival and function of central cholinergic neurons, was significantly increased in several brain areas of old Gdnf^wt/hyper mice. Analysis of expression of genes involved in cholinergic transmission in the cortex and striatum confirmed modulation of cholinergic pathways by GDNF upon aging. In line with these findings, Gdnf^wt/hyper mice did not undergo an age-related decline in cognitive function in the Y-maze test, as observed in the wild type littermates. Our results identify endogenous GDNF as a potential modulator of cholinergic transmission and call for future studies on endogenous GDNF function in neurodegenerative disorders characterized by cognitive impairments, including AD, LBD, and PDD.