Dopamine

L-DOPA ameliorates hippocampus-based mitochondria respiratory dysfunction caused by GCI/R injury

Mitochondrial dysmorphology/dysfunction follow global cerebral ischemia-reperfusion (GCI/R) injury, leading to neuronal death. Our previous researches demonstrated that Levodopa (L-DOPA) improves learning and memory impairment in GCI/R rats by increasing synaptic plasticity of hippocampal neurons. This study investigates if L-DOPA, used in Parkinson's disease treatment, alleviates GCI/R-induced cell death by enhancing mitochondrial quality. Metabolomics and transcriptomic results showed that GCI/R damage affected the Tricarboxylic acid (TCA) cycle in the hippocampus. The results of this study show that L-DOPA stabilized mitochondrial membrane potential and ultrastructure in hippocampus of GCI/R rats, increased dopamine level in hippocampus, decreased succinic acid level, and stabilized Ca2+ level in CA1 subregion of hippocampus. As a precursor of dopamine, L-DOPA is presumed to improves mitochondrial function in hippocampus of GCI/R rats. However, dopamine cannot cross the blood-brain barrier, so L-DOPA is used in clinical therapy to supplement dopamine. In this investigation, OGD/R models were established in isolated mouse hippocampal neurons (HT22) and primary rat hippocampal neurons. Notably, dopamine exhibited a multifaceted impact, demonstrating inhibition of mitochondrial reactive oxygen species (mitoROS) production, stabilization of mitochondrial membrane potential and Ca2+ level, facilitation of TCA circulation, promotion of aerobic respiratory metabolism, and downregulation of succinic acid-related gene expression. Consistency between in vitro and in vivo results underscores dopamine's significant neuroprotective role in mitigating mitochondrial dysfunction following global cerebral hypoxia and ischemia injury. Supplement dopamine may represent a promising therapy to the cognitive impairment caused by GCI/R injury.

Ferroptosis inhibitors: past, present and future

Ferroptosis is a non-apoptotic mode of programmed cell death characterized by iron dependence and lipid peroxidation. Since the ferroptosis was proposed, researchers have revealed the mechanisms of its formation and continue to explore effective inhibitors of ferroptosis in disease. Recent studies have shown a correlation between ferroptosis and the pathological mechanisms of neurodegenerative diseases, as well as diseases involving tissue or organ damage. Acting on ferroptosis-related targets may provide new strategies for the treatment of ferroptosis-mediated diseases. This article specifically describes the metabolic pathways of ferroptosis and summarizes the reported mechanisms of action of natural and synthetic small molecule inhibitors of ferroptosis and their efficacy in disease. The paper also describes ferroptosis treatments such as gene therapy, cell therapy, and nanotechnology, and summarises the challenges encountered in the clinical translation of ferroptosis inhibitors. Finally, the relationship between ferroptosis and other modes of cell death is discussed, hopefully paving the way for future drug design and discovery.

Dopamine Pharmacodynamics: New Insights

Dopamine is a key neurotransmitter involved in physiological processes such as motor control, motivation, reward, cognitive function, and maternal and reproductive behaviors. Therefore, dysfunctions of the dopaminergic system are related to a plethora of human diseases. Dopamine, via different circuitries implicated in compulsive behavior, reward, and habit formation, also represents a key player in substance use disorder and the formation and perpetuation of mechanisms leading to addiction. Here, we propose dopamine as a model not only of neurotransmission but also of neuromodulation capable of modifying neuronal architecture. Abuse of substances like methamphetamine, cocaine, and alcohol and their consumption over time can induce changes in neuronal activities. These modifications lead to synaptic plasticity and finally to morphological and functional changes, starting from maladaptive neuro-modulation and ending in neurodegeneration.

Dopamine and acetylcholine correlations in the nucleus accumbens depend on behavioral task states

Dopamine in the nucleus accumbens ramps up as animals approach desired goals. These ramps have received intense scrutiny because they seem to violate long-held hypotheses on dopamine function. Furthermore, it has been proposed that they are driven by local acetylcholine release, i.e., that they are mechanistically separate from dopamine signals related to reward prediction errors. Here, we tested this hypothesis by simultaneously recording accumbal dopamine and acetylcholine signals in rats executing a task involving motivated approach. Contrary to recent reports, we found that dopamine ramps were not coincidental with changes in acetylcholine. Instead, we found that acetylcholine could be positively, negatively, or uncorrelated with dopamine depending on whether the task phase was determined by a salient cue, reward prediction error, or active approach, respectively. Our results suggest that accumbal dopamine and acetylcholine are largely independent but may combine to engage different postsynaptic mechanisms depending on the behavioral task states.

Highly sensitive and simultaneous detection of ascorbic acid, dopamine, and uric acid using Pt@g-C3N4/N-CNTs nanocomposites

The detection of ascorbic acid (AA), dopamine (DA), and uric acid (UA) is crucial for understanding and managing various illnesses. In this research, Pt@g-C3N4 nanoparticles were synthesized via hydrothermal method and combined with N-doped carbon nanotubes (N-CNTs). The Pt@g-C3N4/N-CNTs-modified glassy carbon (GC) electrode was fabricated as an electrochemical sensor for the determination of AA, DA, and UA. The linear response range of AA, DA, and UA in the optimal condition was 100-3,000 μM, 1-100 μM, and 2-215 μM boasting a low detection limit (S/N = 3) of 29.44 μM (AA), 0.21 μM (UA), and 2.99 μM (DA), respectively. Additionally, the recoveries of AA, DA, and UA in serum sample were 100.4%-106.7%. These results corroborate the feasibility of the proposed method for the simultaneous, sensitive, and reliable detection of AA, DA, and UA. Our Pt@g-C3N4/N-CNTs/GC electrode can provide a potential strategy for disease diagnosis and health monitoring in clinical settings.

Apathy and Motivation: Biological Basis and Drug Treatment

Apathy is a disabling syndrome associated with poor functional outcomes that is common across a broad range of neurological and psychiatric conditions. Currently, there are no established therapies specifically for the condition, and safe and effective treatments are urgently needed. Advances in the understanding of motivation and goal-directed behavior in humans and animals have shed light on the cognitive and neurobiological mechanisms contributing to apathy, providing an important foundation for the development of new treatments. Here, we review the cognitive components, neural circuitry, and pharmacology of apathy and motivation, highlighting converging evidence of shared transdiagnostic mechanisms. Though no pharmacological treatments have yet been licensed, we summarize trials of existing and novel compounds to date, identifying several promising candidates for clinical use and avenues of future drug development.

Gut liver brain axis in diseases: the implications for therapeutic interventions

Gut-liver-brain axis is a three-way highway of information interaction system among the gastrointestinal tract, liver, and nervous systems. In the past few decades, breakthrough progress has been made in the gut liver brain axis, mainly through understanding its formation mechanism and increasing treatment strategies. In this review, we discuss various complex networks including barrier permeability, gut hormones, gut microbial metabolites, vagus nerve, neurotransmitters, immunity, brain toxic metabolites, β-amyloid (Aβ) metabolism, and epigenetic regulation in the gut-liver-brain axis. Some therapies containing antibiotics, probiotics, prebiotics, synbiotics, fecal microbiota transplantation (FMT), polyphenols, low FODMAP diet and nanotechnology application regulate the gut liver brain axis. Besides, some special treatments targeting gut-liver axis include farnesoid X receptor (FXR) agonists, takeda G protein-coupled receptor 5 (TGR5) agonists, glucagon-like peptide-1 (GLP-1) receptor antagonists and fibroblast growth factor 19 (FGF19) analogs. Targeting gut-brain axis embraces cognitive behavioral therapy (CBT), antidepressants and tryptophan metabolism-related therapies. Targeting liver-brain axis contains epigenetic regulation and Aβ metabolism-related therapies. In the future, a better understanding of gut-liver-brain axis interactions will promote the development of novel preventative strategies and the discovery of precise therapeutic targets in multiple diseases.

Research Progress on Effects of Ginsenoside Rg2 and Rh1 on Nervous System and Related Mechanisms

Neurological-related disorders are diseases that affect the body's neurons or peripheral nerve tissue, such as Parkinson's disease (PD) and Alzheimer's disease (AD). The development of neurological disorders can cause serious harm to the quality of life and functioning of the patient. The use of traditional therapeutic agents such as dopamine-promoting drugs, anticholinergic drugs, cholinesterase inhibitors, and NMDA receptor antagonists is often accompanied by a series of side effects such as drug resistance, cardiac arrhythmia, liver function abnormalities, and blurred vision. Therefore, there is an urgent need to find a therapeutic drug with a high safety profile and few side effects. Herbal medicines are rich in active ingredients that are natural macromolecules. Ginsenoside is the main active ingredient of ginseng, which has a variety of pharmacological effects and is considered to have potential value in the treatment of human diseases. Modern pharmacological studies have shown that ginsenosides Rg2 and Rh1 have strong pharmacological activities in the nervous system, with protective effects on nerve cells, improved resistance to neuronal injury, modulation of neural activity, resistance to cerebral ischemia/reperfusion injury, improvement of brain damage after eclampsia hemorrhage, improvement of memory and cognitive deficits, treatment of AD and vascular dementia, alleviation of anxiety, pain, and inhibition of ionic-like behavior. In this article, we searched the pharmacological research literature of Rg2 and Rh1 in the field of neurological diseases, summarized the latest research progress of the two ginsenosides, and reviewed the pharmacological effects and mechanisms of Rg2 and Rh1, which provided a new way of thinking for the research of the active ingredients in ginseng anti-neurological diseases and the development of new drugs.

Mobilization of endocannabinoids by midbrain dopamine neurons is required for the encoding of reward prediction

Brain levels of the endocannabinoid 2-arachidonoylglycerol (2-AG) shape motivated behavior and nucleus accumbens (NAc) dopamine release. However, it is not clear whether mobilization of 2-AG specifically from midbrain dopamine neurons is necessary for dopaminergic responses to external stimuli predicting forthcoming reward. Here, we use a viral-genetic strategy to prevent the expression of the 2-AG-synthesizing enzyme diacylglycerol lipase α (DGLα) from ventral tegmental area (VTA) dopamine cells in adult mice. We find that DGLα deletion from VTA dopamine neurons prevents depolarization-induced suppression of excitation (DSE), a form of 2-AG-mediated synaptic plasticity, in dopamine neurons. DGLα deletion also decreases effortful, cue-driven reward-seeking but has no effect on non-cued or low-effort operant tasks and other behaviors. Moreover, dopamine recording in the NAc reveals that deletion of DGLα impairs the transfer of accumbal dopamine signaling from a reward to its earliest predictors. These results demonstrate that 2-AG mobilization from VTA dopamine neurons is a necessary step for the generation of dopamine-based predictive associations that are required to direct and energize reward-oriented behavior.

A differential strategy to enhance the anti-interference ability of molecularly imprinted electrochemiluminescence sensor with a semi-logarithmic calibration curve

The non-specific adsorption behaviors of various interferents on the surface of a molecularly imprinted polymer (MIP) are adverse for the selectivity of an MIP-based sensor, which can be overcome via a differential strategy by using the differential signal between MIP- and non-imprinted polymer (NIP)-based sensors. However, the normal differential mode is not suitable for the MIP-based sensors with non-linear calibration curves. Herein, an improved differential strategy is reported for an MIP-based sensor with a semi-logarithmic calibration curve, demonstrated by an electrochemiluminescence (ECL) sensor for dopamine (DA). Glassy carbon electrode (GCE) was modified by the mixture of g-C3N4, TiO2 nanoparticles (NPs) and carbon nanotubes (CNTs). MIP membrane for DA was fabricated on the surface of g-C3N4/TiO2NPs/CNTs/GCE using chitosan for film-forming, obtained MIP@GCE. To enhance the anti-interference ability of the MIP-based DA sensor, the difference between exponential functions ECL intensities of MIP@GCE and NIP@GCE is used as the analytical signal in the improved differential strategy. The differential signal was increased linearly with increasing DA concentration ranging from 10 pM to 0.10 μM, with the detection limit of 5.6 pM. The interference level of Cu2+ on DA determination in the improved differential mode is only 9.7% of that in the normal MIP mode. The improved differential strategy can be used in other MIP-based sensors with semi-logarithmic calibration curves.

Carbon dots with light-responsive oxidase-like activity for colorimetric detection of dopamine and the catalytic mechanism

Introduction: Dopamine is one of the most significant neurotransmitters and plays an important role in the management of cognitive functions such as learning, memory, and behavior. The disorder of dopamine is associated with many major mental diseases. It is necessary to develop selective methods for the detection of dopamine. Methods: In this work, carbon dots (CDs) were synthesized by a solvothermal route using glutathione, L-histidine, and formamide as sources. Results: Under light irradiation, The CDs convert dissolved oxygen to singlet oxygen (1O2), which could oxidize TMB. When reduced dopamine was present, it suppressed the catalysis of CDs, then the absorption of the CDs-coupled TMB complex at 652 nm was diminished. Furthermore, it was revealed that the surface groups including hydroxyl, amino, carbonyl, and carboxyl groups of CDs were related to their light-responsive catalytic activity by surface modification. In the range of 0.5-15 μM, the CDs could afford a LOD of 0.25 μM for dopamine detection with fine linearity, also showing good selectivity. Discussion: The results from fetal bovine serum indicated the good applicability of the CDs in the determination of dopamine.

Multicolor colorimetric detection of dopamine based on iodide-responsive copper-gold nanoparticles

Dopamine (DA) is one of the most essential catecholamine neurotransmitters in the human body. A rapid colorimetric detection method for DA in urine and serum was established in this work using unmodified iodide-responsive copper-gold nanoparticles (Cu-Au NPs). The detection method provides a rapid response with color variability within 15 min at room temperature. In addition, the colorimetric probe has elevated stability, excellent selectivity and resistance to interference.

Declining locus coeruleus-dopaminergic and noradrenergic modulation of long-term memory in aging and Alzheimer's disease

Memory is essential in defining our identity by guiding behavior based on past experiences. However, aging leads to declining memory, disrupting older adult's lives. Memories are encoded through experience-dependent modifications of synaptic strength, which are regulated by the catecholamines dopamine and noradrenaline. While cognitive aging research demonstrates how dopaminergic neuromodulation from the substantia nigra-ventral tegmental area regulates hippocampal synaptic plasticity and memory, recent findings indicate that the noradrenergic locus coeruleus sends denser inputs to the hippocampus. The locus coeruleus produces dopamine as biosynthetic precursor of noradrenaline, and releases both to modulate hippocampal plasticity and memory. Crucially, the locus coeruleus is also the first site to accumulate Alzheimer's-related abnormal tau and severely degenerates with disease development. New in-vivo assessments of locus coeruleus integrity reveal associations with Alzheimer's markers and late-life memory impairments, which likely stem from impaired dopaminergic and noradrenergic neurotransmission. Bridging research across species, the reviewed findings suggest that degeneration of the locus coeruleus results in deficient dopaminergic and noradrenergic modulation of hippocampal plasticity and thus memory decline.

Dissociable effects of dopaminergic medications on depression symptom dimensions in Parkinson's disease

Background

Depression in Parkinson's disease (PD) is common, disabling and responds poorly to standard antidepressant medication. Motivational symptoms of depression, such as apathy and anhedonia, are particularly prevalent in depression in PD and predict poor response to antidepressant treatment. Loss of dopaminergic innervation of the striatum is associated with emergence of motivational symptoms in PD, and mood fluctuations correlate with dopamine availability. Accordingly, optimising dopaminergic treatment for PD can improve depressive symptoms, and dopamine agonists have shown promising effects in improving apathy. However, the differential effect of antiparkinsonian medication on symptom dimensions of depression is not known.

Aims

We hypothesised that there would be dissociable effects of dopaminergic medications on different depression symptom dimensions. We predicted that dopaminergic medication would specifically improve motivational symptoms, but not other symptoms, of depression. We also hypothesised that antidepressant effects of dopaminergic medications with mechanisms of action reliant on pre-synaptic dopamine neuron integrity would attenuate as pre-synaptic dopaminergic neurodegeneration progresses.

Methods

We analysed data from a longitudinal study of 412 newly diagnosed PD patients followed over five years in the Parkinson's Progression Markers Initiative cohort. Medication state for individual classes of Parkinson's medications was recorded annually. Previously validated "motivation" and "depression" dimensions were derived from the 15-item geriatric depression scale. Dopaminergic neurodegeneration was measured using repeated striatal dopamine transporter (DAT) imaging.

Results

Linear mixed-effects modelling was performed across all simultaneously acquired data points. Dopamine agonist use was associated with relatively fewer motivation symptoms as time progressed (interaction: β=-0.07, 95%CI [-0.13,-0.01], p=0.015) but had no effect on the depression symptom dimension (p=0.6). In contrast, monoamine oxidase-B (MAO-B) inhibitor use was associated with relatively fewer depression symptoms across all years (β=-0.41, 95%CI [-0.81,-0.01], p=0.047). No associations were observed between either depression or motivation symptoms and levodopa or amantadine use. There was a significant interaction between striatal DAT binding and MAO-B inhibitor use on motivation symptoms: MAO-B inhibitor use was associated with lower motivation symptoms in patients with higher striatal DAT binding (interaction: β=-0.24, 95%CI [-0.43, -0.05], p=0.012). No other medication effects were moderated by striatal DAT binding measures.

Conclusions

We identified dissociable associations between dopaminergic medications and different dimensions of depression in PD. Dopamine agonists may be effective for treatment of motivational symptoms of depression. In contrast, MAO-B inhibitors may improve both depressive and motivation symptoms, albeit the latter effect appears to be attenuated in patients with more severe striatal dopaminergic neurodegeneration, which may be a consequence of dependence on pre-synaptic dopaminergic neuron integrity.

A multivariate regressor of patterned dopamine release predicts relapse to cocaine

Understanding mesolimbic dopamine adaptations underlying vulnerability to drug relapse is essential to inform prognostic tools for effective treatment strategies. However, technical limitations have hindered the direct measurement of sub-second dopamine release in vivo for prolonged periods of time, making it difficult to gauge the weight that these dopamine abnormalities have in determining future relapse incidence. Here, we use the fluorescent sensor GrabDA to record, with millisecond resolution, every single cocaine-evoked dopamine transient in the nucleus accumbens (NAc) of freely moving mice during self-administration. We reveal low-dimensional features of patterned dopamine release that are strong predictors of cue-induced reinstatement of cocaine seeking. Additionally, we report sex-specific differences in cocaine-related dopamine responses related to a greater resistance to extinction in males compared with females. These findings provide important insights into the sufficiency of NAc dopamine signaling dynamics-in interaction with sex-for recapitulating persistent cocaine seeking and future relapse vulnerability.

Reappraising the role of dopamine in adolescent risk-taking behavior

Adolescence is characterized by increased risk-taking, which is often ascribed to developmental changes in dopaminergic signaling. Popular models propose that these behaviors are caused by dopamine-induced hypersensitivity to rewards, which overrides adolescents' immature self-control mechanisms. However, these models are often based on oversimplified notions about the workings and functions of dopamine. Here we discuss the relationship between changes in the dopaminergic system and adolescent behavior in light of current theories/models about the functions of dopamine. We show that dopamine is linked to learning, adaptive decision-making under uncertainty, and increased motivation to work for rewards. Thus, changes in the dopaminergic system contribute to the maturation of cognitive control through various mechanisms, contrary to the false dichotomy between reward processing and self-control. Finally, we note that dopamine interacts with a number of other neuromodulator systems, which also change during adolescence, but that have been largely ignored in the field of adolescent development. A full understanding of adolescent behavior will require these neurochemicals and their interactions with dopamine to be taken into account.

Optogenetic inhibition of the caudal substantia nigra inflates behavioral responding to uncertain threat and safety

Defensive responding is adaptive when it approximates current threat, but maladaptive when it exceeds current threat. Here we asked if the substantia nigra, a region consistently implicated in reward, is necessary to show appropriate levels of defensive responding in Pavlovian fear discrimination. Rats received bilateral transduction of the caudal substantia nigra with halorhodopsin or a control fluorophore, and bilateral ferrule implants. Rats then behaviorally discriminated cues predicting unique foot shock probabilities (danger, p =1; uncertainty, p =0.25; and safety, p =0). Green-light illumination (532 nm) during cue presentation inflated defensive responding of halorhodopsin rats - measured by suppression of reward seeking - to uncertainty and safety beyond control levels. Green-light illumination outside of cue presentation had no impact on halorhodopsin or control rat responding. The results reveal caudal substantia nigra cue activity is necessary to inhibit defensive responding to non-threatening and uncertain threat cues.

Advances in Hemostatic Hydrogels That Can Adhere to Wet Surfaces

Currently, uncontrolled bleeding remains a serious problem in emergency, surgical and battlefield environments. Despite the specific properties of available hemostatic agents, sealants, and adhesives, effective hemostasis under wet and dynamic conditions remains a challenge. In recent years, polymeric hydrogels with excellent hemostatic properties have received much attention because of their adjustable mechanical properties, high porosity, and biocompatibility. In this review, to investigate the role of hydrogels in hemostasis, the mechanisms of hydrogel hemostasis and adhesion are firstly elucidated, the adhesion design strategies of hemostatic hydrogels in wet environments are briefly introduced, and then, based on a comprehensive literature review, the studies and in vivo applications of wet-adhesive hemostatic hydrogels in different environments are summarized, and the improvement directions of such hydrogels in future studies are proposed.