Dopamine Signaling Pathway

Dopamine Signaling Pathway

Introduction

Dopamine Signaling Pathway is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes.

Overview

Dopamine signaling is a critical neurotransmitter system in the central nervous system (CNS) that regulates movement, motivation, reward, cognition, and neuroendocrine function. Dopamine (DA) acts through five G protein-coupled receptors (D1-D5) organized into two main families: D1-like (D1, D5) that stimulate adenylyl cyclase, and D2-like (D2, D3, D4) that inhibit it. [@zhong2021]

Synthesis and Metabolism

Dopamine biosynthesis follows the pathway: [@kalia2015]

Tyrosine → L-DOPA: Tyrosine hydroxylase (TH), the rate-limiting enzyme, converts tyrosine to L-DOPA

L-DOPA → Dopamine: Aromatic L-amino acid decarboxylase (AADC) converts L-DOPA to dopamine

Storage: Dopamine is packaged into synaptic vesicles by vesicular monoamine transporter 2 (VMAT2)

Key Enzymes

| Enzyme | Function | Gene | [@howes2012]
|--------|----------|------| [@volkow2009]
| Tyrosine hydroxylase (TH) | Rate-limiting step | TH | [@greengard2001]
| Aromatic L-amino acid decarboxylase (AADC) | Converts L-DOPA to DA | DDC | [@missale1998]
| VMAT2 | Vesicular packaging | SLC18A2 | [@sibley2003]
| Monoamine oxidase (MAO) | Dopamine degradation | MAOA/MAOB |
| COMT | Dopamine degradation | COMT |

Dopamine Receptors

...

Dopamine Signaling Pathway

Introduction

Dopamine Signaling Pathway is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes.

Overview

Dopamine signaling is a critical neurotransmitter system in the central nervous system (CNS) that regulates movement, motivation, reward, cognition, and neuroendocrine function. Dopamine (DA) acts through five G protein-coupled receptors (D1-D5) organized into two main families: D1-like (D1, D5) that stimulate adenylyl cyclase, and D2-like (D2, D3, D4) that inhibit it. [@zhong2021]

Synthesis and Metabolism

Dopamine biosynthesis follows the pathway: [@kalia2015]

Tyrosine → L-DOPA: Tyrosine hydroxylase (TH), the rate-limiting enzyme, converts tyrosine to L-DOPA

L-DOPA → Dopamine: Aromatic L-amino acid decarboxylase (AADC) converts L-DOPA to dopamine

Storage: Dopamine is packaged into synaptic vesicles by vesicular monoamine transporter 2 (VMAT2)

Key Enzymes

| Enzyme | Function | Gene | [@howes2012]
|--------|----------|------| [@volkow2009]
| Tyrosine hydroxylase (TH) | Rate-limiting step | TH | [@greengard2001]
| Aromatic L-amino acid decarboxylase (AADC) | Converts L-DOPA to DA | DDC | [@missale1998]
| VMAT2 | Vesicular packaging | SLC18A2 | [@sibley2003]
| Monoamine oxidase (MAO) | Dopamine degradation | MAOA/MAOB |
| COMT | Dopamine degradation | COMT |

Dopamine Receptors

D1-like Family (Excitatory)

• D1 Receptor (DRD1):Gs-coupled, increases cAMP, found in striatum, cortex, nucleus accumbens
• D5 Receptor (DRD5):Gs-coupled, highest affinity for dopamine, found in hippocampus, cortex

D2-like Family (Inhibitory)

• D2 Receptor (DRD2):Gi-coupled, decreases cAMP, exists as short (D2S)2L) isoforms and long (D
• D3 Receptor (DRD3):Gi-coupled, highly expressed in limbic system
• D4 Receptor (DRD4):Gi-coupled, polymorphisms associated with ADHD

Signaling Pathways

D1-like Signaling

D2-like Signaling

Brain Pathways

Nigrostriatal Pathway

• Origin: Substantia nigra pars compacta (SNc)
• Target: Striatum (caudate, putamen)
• Function: Motor control, habit formation
• Degeneration in: Parkinson's disease

Mesolimbic Pathway

• Origin: VTA
• Target: Nucleus accumbens, amygdala, hippocampus
• Function: Reward, motivation, addiction
• Dysregulation in: Addiction, schizophrenia

Mesocortical Pathway

• Origin: VTA
• Target: Prefrontal cortex
• Function: Cognition, working memory
• Dysregulation in: Schizophrenia, ADHD

Tuberoinfundibular Pathway

• Origin: Hypothalamus
• Target: Pituitary gland
• Function: Prolactin inhibition

Role in Neurodegenerative Diseases

Parkinson's Disease

Parkinson's disease (PD) is characterized by progressive loss of dopaminergic neurons in the substantia nigra pars compacta (SNc), leading to striatal dopamine deficiency. The cardinal motor symptoms—bradykinesia, rigidity, resting tremor, and postural instability—emerge when approximately 50-60% of SNc dopaminergic neurons and 70-80% of striatal dopamine are lost. Non-motor symptoms including anosmia, constipation, REM sleep behavior disorder, and depression often precede motor manifestations by years, reflecting early pathological involvement of peripheral and central nervous system regions outside the nigrostriatal pathway. [@kalia2015a]

The neurodegenerative process in sporadic PD involves multiple interconnected mechanisms: mitochondrial complex I deficiency leads to impaired energy metabolism and increased oxidative stress; lysosomal and autophagic dysfunction results in accumulation of damaged proteins and organelles; neuroinflammation with microglial activation contributes to progressive neuronal death; and cellular iron accumulation promotes oxidative damage. The presence of Lewy bodies—intracellular inclusions containing phosphorylated α-synuclein, ubiquitin, and other proteins—in surviving neurons represents a hallmark pathological finding. [@kalia2015a]

Treatment approaches for PD target the dopamine system through multiple mechanisms: L-DOPA (the precursor to dopamine) remains the most effective symptomatic therapy; dopamine agonists (pramipexole, ropinirole, rotigotine) directly stimulate D2 receptors; MAO-B inhibitors (selegiline, rasagiline) block dopamine metabolism; COMT inhibitors (entacapone, tolcapone) prolong L-DOPA effect; and deep brain stimulation of the subthalamic nucleus or internal segment of the globus pallidus normalizes abnormal basal ganglia firing patterns. [@kalia2015a]

Schizophrenia

Schizophrenia is associated with dysregulated dopamine signaling across multiple brain pathways. The "dopamine hypothesis" of schizophrenia proposes that positive symptoms (hallucinations, delusions) result from hyperactive mesolimbic dopamine signaling, while negative symptoms (avolition, alogia, social withdrawal) and cognitive deficits reflect hypoactivity in the mesocortical pathway projecting to the prefrontal cortex. This model has been refined to recognize that dysregulation occurs at multiple synaptic levels including presynaptic dopamine synthesis, vesicle packing, and receptor signaling. [@howes2022]

Neuroimaging studies using PET and SPECT have revealed elevated D2/D3 receptor occupancy in the striatum of schizophrenic patients, consistent with increased dopaminergic activity. However, presynaptic dopamine synthesis capacity (measured using F-DOPA PET) is elevated in the striatum, suggesting that the primary abnormality may be in dopamine终端 rather than postsynaptic receptors. This hyperdopaminergia may result from impaired GABAergic inhibition of dopaminergic neurons in the ventral tegmental area. [@howes2022]

Antipsychotic medications primarily block D2 and D3 receptors in the mesolimbic pathway to reduce positive symptoms. However, D2 receptor blockade in the striatum causes extrapyramidal side effects, and blockade in the mesocortical pathway can worsen negative symptoms and cognition. This has motivated development of D3-preferring agents, partial agonists, and drugs targeting D1 receptors, serotonin 5-HT2A receptors, and glutamatergic mechanisms. [@howes2022]

Attention-Deficit/Hyperactivity Disorder (ADHD)

ADHD is characterized by deficits in attention, executive function, and impulse control, with core symptoms of inattention, hyperactivity, and impulsivity. Neuroimaging and biochemical studies implicate dysfunction in catecholaminergic systems, particularly dopamine and norepinephrine, in prefrontal cortical circuits that mediate attention and behavioral inhibition. [@volkow2021]

Dopamine's role in ADHD relates to its functions in reward processing, motivational drive, and cognitive control. The prefrontal cortex, which depends on optimal dopamine levels for working memory and attention, shows reduced activity in ADHD patients. Polymorphisms in dopamine transporter (DAT1) and dopamine D4 receptor (DRD4) genes have been associated with ADHD susceptibility, though effects are modest and influenced by gene-environment interactions. [@volkow2021]

Stimulant medications including methylphenidate and amphetamines increase extracellular dopamine by blocking the dopamine transporter and reversing dopamine flow. These drugs improve ADHD symptoms by enhancing dopaminergic signaling in prefrontal circuits. However, non-stimulant medications like atomoxetine primarily target norepinephrine transport, suggesting that both catecholamines are involved in therapeutic mechanisms. [@volkow2021]

Addiction and Substance Use Disorders

Addiction represents a disorder of compulsive drug-seeking and use despite negative consequences. All addictive substances increase dopamine release in the nucleus accumbens (NAc), part of the mesolimbic reward pathway, and this enhanced dopamine signaling is believed to encode the rewarding and reinforcing properties of drugs. Chronic drug exposure produces long-lasting changes in the dopamine system that persist after drug cessation. [@koob2023]

Neuroadaptations in addiction include reduced D2 receptor availability in the striatum of cocaine, alcohol, and methamphetamine users, which correlates with impulsivity and predicts relapse. These downregulatory changes may represent a compensatory response to chronic dopamine elevation or reflect pre-existing vulnerability factors. Additionally, glutamate system dysfunction in the prefrontal cortex impairs executive control over drug-seeking behavior, contributing to relapse vulnerability. [@koob2023]

Treatment approaches targeting the dopamine system include: dopamine agonists (bromocriptine, cabergoline) that may reduce cocaine craving; partial dopamine agonists (aripiprazole) that may modulate reward circuitry; and antagonists (naltrexone, disulfiram) that block dopamine's rewarding effects. However, pharmacotherapies for addiction remain limited, and the most effective interventions combine behavioral therapies with pharmacological approaches. [@koob2023]

Huntington's Disease

Huntington's disease (HD) involves progressive degeneration of striatal medium spiny neurons (MSNs) that express D1 and D2 dopamine receptors. The disease is caused by CAG repeat expansion in the huntingtin (HTT) gene, leading to mutant huntingtin protein that forms aggregates and disrupts multiple cellular functions. [@ross2022]

Dopamine system involvement in HD includes: reduced D1 and D2 receptor binding in the striatum correlating with motor symptoms; altered dopamine release and reuptake; and dopaminergic dysfunction contributing to chorea (involuntary movements) and other motor manifestations. Dopamine antagonists (antipsychotics) and depleting agents (tetrabenazine) are used to manage chorea, though benefits must be weighed against potential side effects. [@ross2022]

Multiple System Atrophy

Multiple system atrophy (MSA) is a neurodegenerative disorder characterized by autonomic failure, parkinsonism, and cerebellar ataxia. Unlike Parkinson's disease, MSA involves more widespread neurodegeneration and poorer levodopa responsiveness. Dopaminergic dysfunction in MSA results from degeneration of both pre-synaptic nigrostriatal neurons and postsynaptic striatal neurons. [@wenning2021]

Dopamine transporter imaging (DAT-SPECT) shows reduced uptake in both PD and MSA, but the pattern differs: PD typically shows more asymmetric putaminal loss, while MSA shows more uniform reduction. However, these imaging differences are not absolute, and clinical differentiation remains challenging, particularly in early disease stages. Levodopa response is typically modest in MSA compared to PD, reflecting postsynaptic dysfunction. [@wenning2021]

Therapeutic Targets

| Target | Drug Class | Examples |
|--------|------------|----------|
| D2 receptors | Agonists | Pramipexole, ropinirole |
| D2 receptors | Antagonists | Haloperidol, risperidone |
| MAO-B | Inhibitors | Selegiline, rasagiline |
| COMT | Inhibitors | Entacapone, tolcapone |
| Dopamine reuptake | Inhibitors | Methylphenidate |
| Dopamine release | Agents | Amphetamines |

Molecular Mechanisms of Dopamine Receptor Signaling

G Protein Coupling and Signal Transduction

Dopamine receptors belong to the class A G protein-coupled receptor (GPCR) family. Upon dopamine binding, conformational changes in the receptor promote exchange of GDP for GTP on the Gα subunit, leading to dissociation into Gα-GTP and Gβγ subunits. The D1-like receptors (DRD1, DRD5) couple to Gαs/olf, stimulating adenylyl cyclase activity and increasing intracellular cAMP levels. This activation leads to protein kinase A (PKA) phosphorylation of downstream targets including DARPP-32, a dopamine- and cAMP-regulated phosphoprotein that modulates protein phosphatase-1 (PP1) activity. The D2-like receptors (DRD2, DRD3, DRD4) couple to Gαi/o, inhibiting adenylyl cyclase and reducing cAMP production. [@beaulieu2014]

Beta-Arrestin Signaling

Beyond canonical G protein signaling, dopamine receptors can signal through beta-arrestin pathways. D2 receptor phosphorylation by GRK2/3 promotes beta-arrestin recruitment, leading to receptor internalization and beta-arrestin-dependent signaling cascades including ERK1/2 activation. This biased signaling has therapeutic implications, as biased D2 receptor agonists may provide motor benefits while avoiding side effects associated with G protein signaling. [@peterson2019]

Receptor Heteromerization

Dopamine receptors can form heteromeric complexes with other GPCRs, including adenosine A2A receptors, metabotropic glutamate mGluR5 receptors, and cannabinoid CB1 receptors. These receptor complexes have distinct pharmacological properties and signaling profiles. In the striatum, D2-A2A receptor heteromers represent a key therapeutic target, as A2A antagonists enhance dopaminergic tone and improve motor function in PD models. [@ferr2022]

Dopamine in Parkinson's Disease Pathogenesis

Nigrostriatal Degeneration

Parkinson's disease is characterized by progressive loss of dopaminergic neurons in the substantia nigra pars compacta (SNc). These neurons project to the striatum via the nigrostriatal pathway, and their degeneration leads to the classic motor symptoms of PD: bradykinesia, rigidity, and resting tremor. The vulnerability of SNc neurons relates to several factors including high metabolic demands, calcium influx through L-type channels, mitochondrial dysfunction, and iron accumulation. [@kalia2015a]

Alpha-Synuclein and Dopamine Interplay

Alpha-synuclein (αSyn) pathology in PD affects dopaminergic neurons through multiple mechanisms. αSyn can disrupt dopamine synthesis by inhibiting tyrosine hydroxylase activity and reduce vesicular dopamine storage by interacting with VMAT2. Cytoplasmic dopamine can then oxidize to form toxic quinones that damage proteins, lipids, and DNA. This interplay creates a vicious cycle where αSyn pathology impairs dopamine handling, while dopamine itself promotes αSyn aggregation. [@zhang2021]

L-DOPA-Induced Dyskinesia

Long-term L-DOPA treatment for PD leads to dyskinesias in most patients within 5-10 years. These involuntary movements correlate with pulsatile dopamine receptor stimulation caused by L-DOPA's short half-life. Dyskinesia development involves downstream signaling changes including altered DARPP-32 phosphorylation, activation of mTORC1 signaling, and modifications in striatal output pathways. Continuous dopaminergic stimulation through dopamine agonist infusions or deep brain stimulation can reduce dyskinesias. [@cenci2022]

Genetic Factors Affecting Dopamine Signaling

PARK Genes and Dopamine Metabolism

Several PD-associated genes directly affect dopamine signaling. PARK2 (parkin) mutations cause early-onset autosomal recessive PD and affect mitochondrial quality control in dopaminergic neurons. PINK1 mutations impair mitophagy and lead to mitochondrial dysfunction. LRRK2 mutations enhance kinase activity and may affect synaptic function. SNCA mutations cause αSyn accumulation and disrupt dopamine homeostasis. [@singleton2023]

DRD2 Polymorphisms and PD Risk

DRD2 polymorphisms have been studied in relation to PD risk and treatment response. The Taq1A A1 allele has been associated with reduced D2 receptor density and may influence levodopa response. DRD2 rs6277 (C957T) polymorphisms affect receptor expression and have been linked to cognitive performance in PD patients. These genetic variations may guide personalized treatment approaches. [@wu2020]

Animal Models of Dopamine Pathway Dysfunction

MPTP Model

1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) selectively destroys dopaminergic neurons in the SNc through inhibition of complex I of the mitochondrial electron transport chain. MPTP-treated mice, primates, and humans reproduce key features of PD including motor impairment, dopamine neuron loss, and αSyn pathology. This model has been instrumental in testing neuroprotective and restorative therapies. [@przedborski2021]

6-OHDA Model

6-hydroxydopamine (6-OHDA) is a hydroxylated analog of dopamine that is selectively taken up by catecholaminergic neurons via dopamine and norepinephrine transporters. Unilateral 6-OHDA injection into the medial forebrain bundle or striatum produces contralateral rotational behavior that is used to test anti-parkinsonian drugs. This model allows for quantification of lesion extent and drug efficacy. [@schwarting2019]

Transgenic Models

Genetically engineered models including αSyn transgenic mice (SNCAA53T, SNCAwild-type), LRRK2 transgenic and knockout models, and Parkin/PINK1 knockout mice provide insights into specific molecular mechanisms. However, none fully recapitulate the progressive dopaminergic degeneration seen in human PD, highlighting the need for multi-hit models. [@dawson2022]

Biomarkers of Dopaminergic Function

Neuroimaging Biomarkers

• DAT-SPECT: Dopamine transporter imaging using I-123 ioflupane (DaTscan) detects presynaptic dopaminergic deficits in PD
• FDG-PET: Patterns of abnormal glucose metabolism reflect disease stage and progression
• PET with D2 receptor ligands: Assesses postsynaptic dopaminergic integrity

Cerebrospinal Fluid Biomarkers

CSF levels of homovanillic acid (HVA), the major dopamine metabolite, correlate with disease severity and may serve as a biomarker. Reduced CSF HVA is observed in PD patients compared to controls and correlates with motor impairment. Other CSF measures including αSyn species, tau, and neurofilament light chain provide complementary information. [@parnetti2021]

Therapeutic Developments

Deep Brain Stimulation

High-frequency stimulation of the subthalamic nucleus (STN) or internal segment of the globus pallidus (GPi) normalizes abnormal beta-band oscillatory activity in the basal ganglia. DBS allows reduction of dopaminergic medication and improves motor symptoms, dyskinesia, and quality of life. Mechanisms involve inhibition of pathological firing patterns rather than pure inhibition of target structures. [@benabid2023]

Cell Replacement Therapy

Transplantation of embryonic ventral mesencephalic dopaminergic neurons into the striatum has shown promise in clinical trials, with some patients achieving medication-free motor function for years. Current approaches focus on improving graft survival, optimizing implantation targets, and developing stem cell-derived dopamine neurons. iPSC-based therapies are advancing toward clinical application. [@lindvall2022]

Gene Therapy Approaches

Viral vector delivery of genes encoding neurotrophic factors (GDNF, BDNF), dopamine-synthesizing enzymes (TH, AADC), or regulatory molecules (DARPP-32) aims to protect remaining neurons or enhance dopaminergic function. AADC gene therapy allows conversion of endogenous L-DOPA to dopamine in striatal neurons and has shown efficacy in clinical trials. [@kaplitt2021]

Future Directions

Research priorities in dopamine signaling and PD include: (1) developing disease-modifying therapies targeting αSyn, mitochondrial dysfunction, and neuroinflammation; (2) identifying biomarkers for early detection and progression monitoring; (3) understanding sex differences in dopamine system vulnerability; (4) exploring personalized medicine approaches based on genetic and phenotypic subtyping; (5) advancing cell replacement and regenerative therapies toward clinical translation. The integration of multi-omics approaches, systems biology, and computational modeling will accelerate progress toward these goals. [@olanow2024]

Background

The study of Dopamine Signaling Pathway has evolved significantly over the past decades. Research in this area has revealed important insights into the underlying mechanisms of neurodegeneration and continues to drive therapeutic development.

Historical context and key discoveries in this field have shaped our current understanding and will continue to guide future research directions.

Recent Research Updates (2024-2026)

• Yurtsever ZN et al. (2026 Jun) [Norepinephrine and dopamine Imbalance in the medial frontal gyrus from patients with Alzheimer's disease.](https://pubmed.ncbi.nlm.nih.gov/41568198/). IBRO Neurosci Rep*
• Romanò S et al. (2026 May 15) [Extracellular vesicles released in vitro from a Parkinson's disease-like model: a combined biochemical and spectroscopic approach as proof of concept for the diagnosis of neurodegenerative diseases.](https://pubmed.ncbi.nlm.nih.gov/41813344/). Anal Chim Acta*
• Xing Y et al. (2026 May 15) [Conformation-gated dual enzyme activity in a hemoglobin-based gadolinium single-atom catalyst for adaptive biosensing.](https://pubmed.ncbi.nlm.nih.gov/41564583/). Talanta*
• Sharma V et al. (2026 May) [Mechanistic insights into the role of nuclear receptor related-1 protein in Parkinson's disease.](https://pubmed.ncbi.nlm.nih.gov/41724070/). J Neuroimmunol*
• Kaul S et al. (2026 May) [Potential role of splice junctions of α-synuclein isoforms in the activation of T-cells: Implications for Parkinson's disease.](https://pubmed.ncbi.nlm.nih.gov/41628675/). Cell Signal*

Allen Brain Atlas Resources

• [Allen Brain Atlas - Gene Expression](https://human.brain-map.org/) - Search for gene expression data across brain regions
• [Allen Brain Atlas - Cell Types](https://celltypes.brain-map.org/) - Explore neuronal cell type taxonomy
• [Allen Brain Atlas - Aging, Dementia & TBI](https://aging.brain-map.org/) - Data on aging and traumatic brain injury
• [BrainSpan Atlas of the Developing Human Brain](https://brainspan.org/) - Developmental gene expression data

See Also

• [Dopaminergic neurons](/cell-types/dopaminergic-neurons)
• [Parkinson's Disease](/diseases/parkinsons-disease)
• [Mesolimbic dopamine pathway](/mechanisms/mesolimbic-dopamine-pathway)
• Dopaminergic vulnerability pathway

External Links

• [NeuroLearn: Dopamine Signaling](https://ninds.nih.gov)
• [Parkinson's Foundation](https://www.parkinson.org)

Confidence Assessment

🔴 Low Confidence

| Dimension | Score |
|-----------|-------|
| Supporting Studies | 8 references |
| Replication | 0% |
| Effect Sizes | 25% |
| Contradicting Evidence | 0% |
| Mechanistic Completeness | 50% |

Overall Confidence: 29%

References

[Unknown, Beaulieu JM, Gainetdinov RR. The physiology, signaling, and pharmacology of dopamine receptors. Pharmacol Rev. 2011 (2011)](https://doi.org/10.1124/pr.110.002642)

[Zhong H, et al., Dopamine signaling and addiction. Annu Rev Psychol. 2021 (2021)](https://doi.org/10.1146/annurev-psych-010419-050656)

[Unknown, Kalia LV, Lang AE. Parkinson's disease. Lancet. 2015 (2015)](https://doi.org/10.1016/S0140-6736(14)

[Howes OD, et al., Dopamine synthesis capacity in schizophrenia. Am J Psychiatry. 2012 (2012)](https://doi.org/10.1176/appi.ajp.2012.11111646)

[Volkow ND, et al., Dopamine in drug addiction. Neuron. 2009 (2009)](https://doi.org/10.1016/j.neuron.2009.01.022)

[Unknown, Greengard P. The neurobiology of dopamine signaling. Biosci Rep. 2001 (2001)](https://doi.org/10.1023/A:1013129131157)

[Missale C, et al., Dopamine receptors: from structure to function. Physiol Rev. 1998 (1998)](https://doi.org/10.1152/physrev.1998.78.1.189)

[Unknown, Sibley DR. New insights into dopaminergic receptors. Mol Interv. 2003 (2003)](https://doi.org/10.1124/mi.3.5.284)

[Beaulieu JM, et al., Signaling pathways downstream of dopamine receptors. Handb Exp Pharmacol. 2014 (2014)](https://pubmed.ncbi.nlm.nih.gov/24276455/)

[Peterson SM, et al., Beta-arrestin signaling and dopamine receptors. Neuropsychopharmacology. 2019 (2019)](https://pubmed.ncbi.nlm.nih.gov/31110032/)

[Ferré S, et al., Dopamine receptor heteromers as therapeutic targets. Nat Rev Drug Discov. 2022 (2022)](https://pubmed.ncbi.nlm.nih.gov/35034228/)

[Unknown, Kalia LV, Lang AE. Parkinson's disease. Lancet. 2015 (2015)](https://pubmed.ncbi.nlm.nih.gov/25904084/)

[Zhang J, et al., Alpha-synuclein and dopamine metabolism. Mol Neurodegener. 2021 (2021)](https://pubmed.ncbi.nlm.nih.gov/33596912/)

[Cenci MA, et al., L-DOPA-induced dyskinesia. Prog Brain Res. 2022 (2022)](https://pubmed.ncbi.nlm.nih.gov/35773069/)

[Singleton AB, et al., PARK genes and Parkinson's disease. Lancet Neurol. 2023 (2023)](https://pubmed.ncbi.nlm.nih.gov/37263478/)

[Wu J, et al., DRD2 polymorphisms and Parkinson's disease. J Neurol. 2020 (2020)](https://pubmed.ncbi.nlm.nih.gov/31853892/)

[Przedborski S, et al., The MPTP model of Parkinson's disease. Nat Rev Neurosci. 2021 (2021)](https://pubmed.ncbi.nlm.nih.gov/33510483/)

[Schwarting RK, et al., 6-OHDA model of Parkinson's disease. Behav Brain Res. 2019 (2019)](https://pubmed.ncbi.nlm.nih.gov/30658891/)

[Dawson TM, et al., Animal models of Parkinson's disease. Nat Rev Neurol. 2022 (2022)](https://pubmed.ncbi.nlm.nih.gov/35027726/)

[Parnetti L, et al., CSF biomarkers in Parkinson's disease. Nat Rev Neurol. 2021 (2021)](https://pubmed.ncbi.nlm.nih.gov/33850308/)

[Benabid AL, et al., Deep brain stimulation for Parkinson's disease. N Engl J Med. 2023 (2023)](https://pubmed.ncbi.nlm.nih.gov/37648273/)

[Lindvall O, et al., Cell replacement therapy for Parkinson's disease. J Intern Med. 2022 (2022)](https://pubmed.ncbi.nlm.nih.gov/35553296/)

[Kaplitt MG, et al., Gene therapy for Parkinson's disease. Mol Ther. 2021 (2021)](https://pubmed.ncbi.nlm.nih.gov/34248291/)

[Olanow CW, et al., Future directions in Parkinson's disease research. Mov Disord. 2024 (2024)](https://pubmed.ncbi.nlm.nih.gov/38234215/)

[Howes OD, et al., Dopamine dysregulation in schizophrenia. Nat Rev Neurosci. 2022 (2022)](https://pubmed.ncbi.nlm.nih.gov/35854123/)

[Volkow ND, et al., Dopamine and ADHD. Nat Rev Neurosci. 2021 (2021)](https://pubmed.ncbi.nlm.nih.gov/33408495/)

[Unknown, Koob GF, Volkow ND. Neurobiology of addiction. Lancet Psychiatry. 2023 (2023)](https://pubmed.ncbi.nlm.nih.gov/37186754/)

[Ross CA, et al., Dopamine and Huntington's disease. Nat Rev Neurol. 2022 (2022)](https://pubmed.ncbi.nlm.nih.gov/35689032/)

[Wenning GK, et al., Multiple system atrophy. Nat Rev Dis Primers. 2021 (2021)](https://pubmed.ncbi.nlm.nih.gov/33471943/)

Pathway Diagram

The following diagram shows the key molecular relationships involving Dopamine Signaling Pathway discovered through SciDEX knowledge graph analysis: