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Current Opinion in Neurobiology Aug 2019Dopamine controls motor functions, motivation, and reward-related learning through G-protein coupled receptor signaling. The current working model is that upon release,... (Review)
Review
Dopamine controls motor functions, motivation, and reward-related learning through G-protein coupled receptor signaling. The current working model is that upon release, dopamine diffuses to influence many target cells via wide-spread receptors. Recent studies, however, suggest that dopamine release is fast and generates small signaling hotspots. In this review, we summarize progress on the understanding of the dopamine release apparatus and evaluate how its properties may shape dopamine signaling during firing. We discuss how mechanisms of regulation may act through this machinery and propose that striatal architecture for dopamine signaling may have evolved to support rapid dopamine coding.
Topics: Corpus Striatum; Dopamine; Learning; Motivation; Reward
PubMed: 30769276
DOI: 10.1016/j.conb.2019.01.001 -
Nature Neuroscience Jun 2018Dopamine is a critical modulator of both learning and motivation. This presents a problem: how can target cells know whether increased dopamine is a signal to learn or... (Review)
Review
Dopamine is a critical modulator of both learning and motivation. This presents a problem: how can target cells know whether increased dopamine is a signal to learn or to move? It is often presumed that motivation involves slow ('tonic') dopamine changes, while fast ('phasic') dopamine fluctuations convey reward prediction errors for learning. Yet recent studies have shown that dopamine conveys motivational value and promotes movement even on subsecond timescales. Here I describe an alternative account of how dopamine regulates ongoing behavior. Dopamine release related to motivation is rapidly and locally sculpted by receptors on dopamine terminals, independently from dopamine cell firing. Target neurons abruptly switch between learning and performance modes, with striatal cholinergic interneurons providing one candidate switch mechanism. The behavioral impact of dopamine varies by subregion, but in each case dopamine provides a dynamic estimate of whether it is worth expending a limited internal resource, such as energy, attention, or time.
Topics: Animals; Dopamine; Dopaminergic Neurons; Humans; Learning; Motivation; Signal Transduction
PubMed: 29760524
DOI: 10.1038/s41593-018-0152-y -
Current Opinion in Neurobiology Apr 2021Dopamine neurons have been intensely studied for their roles in reinforcement learning. A dominant theory of how these neurons contribute to learning is through the... (Review)
Review
Dopamine neurons have been intensely studied for their roles in reinforcement learning. A dominant theory of how these neurons contribute to learning is through the encoding of a reward prediction error (RPE) signal. Recent advances in dopamine research have added nuance to RPE theory by incorporating the ideas of sensory prediction error, distributional encoding, and belief states. Further nuance is likely to be added shortly by convergent lines of research on dopamine neuron diversity. Finally, a major challenge is to reconcile RPE theory with other current theories of dopamine function to account for dopamine's role in movement, motivation, and goal-directed planning.
Topics: Dopamine; Dopaminergic Neurons; Motivation; Reinforcement, Psychology; Reward
PubMed: 33197709
DOI: 10.1016/j.conb.2020.10.012 -
Molecules (Basel, Switzerland) Dec 2017: Parkinson's disease is an aggressive and progressive neurodegenerative disorder that depletes dopamine (DA) in the central nervous system. Dopamine replacement... (Review)
Review
: Parkinson's disease is an aggressive and progressive neurodegenerative disorder that depletes dopamine (DA) in the central nervous system. Dopamine replacement therapy, mainly through actual dopamine and its original prodrug l-dopa (LD), faces many challenges such as poor blood brain barrier penetration and decreased response to therapy with time. : The prodrugs described herein are ester, amide, dimeric amide, carrier-mediated, peptide transport-mediated, cyclic, chemical delivery systems and enzyme-models prodrugs designed and made by chemical means, and their bioavailability was studied in animals. A promising ester prodrug for intranasal delivery has been developed. LD methyl ester is currently in Phase III clinical trials. A series of amide prodrugs were synthesized with better stability than ester prodrugs. Both amide and dimeric amide prodrugs offer enhanced blood brain barrier (BBB) penetration and better pharmacokinetics. Attaching LD to sugars has been used to exploit glucose transport mechanisms into the brain. : Till now, no DA prodrug has reached the pharmaceutical market, nevertheless, the future of utilizing prodrugs for the treatment of PD seems to be bright. For instance, LD ester prodrugs have demonstrated an adequate intranasal delivery of LD, thus enabling the absorption of therapeutic agents to the brain. Most of the amide, cyclic, peptidyl or chemical delivery systems of DA prodrugs demonstrated enhanced pharmacokinetic properties.
Topics: Animals; Dopamine; Drug Carriers; Humans; Levodopa; Parkinson Disease; Prodrugs
PubMed: 29295587
DOI: 10.3390/molecules23010040 -
Neuropharmacology 2009Dopamine is involved in drug reinforcement but its role in addiction is less clear. Here we describe PET imaging studies that investigate dopamine's involvement in drug... (Review)
Review
Dopamine is involved in drug reinforcement but its role in addiction is less clear. Here we describe PET imaging studies that investigate dopamine's involvement in drug abuse in the human brain. In humans the reinforcing effects of drugs are associated with large and fast increases in extracellular dopamine, which mimic those induced by physiological dopamine cell firing but are more intense and protracted. Since dopamine cells fire in response to salient stimuli, supraphysiological activation by drugs is experienced as highly salient (driving attention, arousal, conditioned learning and motivation) and with repeated drug use may raise the thresholds required for dopamine cell activation and signaling. Indeed, imaging studies show that drug abusers have marked decreases in dopamine D2 receptors and in dopamine release. This decrease in dopamine function is associated with reduced regional activity in orbitofrontal cortex (involved in salience attribution; its disruption results in compulsive behaviors), cingulate gyrus (involved in inhibitory control; its disruption results in impulsivity) and dorsolateral prefrontal cortex (involved in executive function; its disruption results in impaired regulation of intentional actions). In parallel, conditioning triggered by drugs leads to enhanced dopamine signaling when exposed to conditioned cues, which then drives the motivation to procure the drug in part by activation of prefrontal and striatal regions. These findings implicate deficits in dopamine activity-inked with prefrontal and striatal deregulation-in the loss of control and compulsive drug intake that results when the addicted person takes the drugs or is exposed to conditioned cues. The decreased dopamine function in addicted individuals also reduces their sensitivity to natural reinforcers. Therapeutic interventions aimed at restoring brain dopaminergic tone and activity of cortical projection regions could improve prefrontal function, enhance inhibitory control and interfere with impulsivity and compulsive drug administration while helping to motivate the addicted person to engage in non-drug related behaviors.
Topics: Animals; Brain; Diagnostic Imaging; Dopamine; Humans; Substance-Related Disorders
PubMed: 18617195
DOI: 10.1016/j.neuropharm.2008.05.022 -
Brain and Language Aug 2021Dopamine, the main catecholamine neurotransmitter in the brain, is predominately produced in the basal ganglia and released to various brain regions including the...
Dopamine, the main catecholamine neurotransmitter in the brain, is predominately produced in the basal ganglia and released to various brain regions including the frontal cortex, midbrain and brainstem. Dopamine's effects are widespread and include modulation of a number of voluntary and innate behaviors. Vigilant regulation and modulation of dopamine levels throughout the brain is imperative for proper execution of motor behaviors, in particular speech and other types of vocalizations. While dopamine's role in motor circuitry is widely accepted, its unique function in normal and abnormal speech production is not fully understood. In this perspective, we first review the role of dopaminergic circuits in vocal production. We then discuss and propose the conceivable involvement of astrocytes, the numerous star-shaped glia cells of the brain, in the dopaminergic network modulating normal and abnormal vocal productions.
Topics: Astrocytes; Basal Ganglia; Brain; Dopamine; Humans; Speech
PubMed: 34098250
DOI: 10.1016/j.bandl.2021.104970 -
Journal of Neurochemistry Jun 2021The actions of dopamine are essential to relapse to drug seeking but we still lack a precise understanding of how dopamine achieves these effects. Here we review recent... (Review)
Review
The actions of dopamine are essential to relapse to drug seeking but we still lack a precise understanding of how dopamine achieves these effects. Here we review recent advances from animal models in understanding how dopamine controls relapse to drug seeking. These advances have been enabled by important developments in understanding the basic neurochemical, molecular, anatomical, physiological and functional properties of the major dopamine pathways in the mammalian brain. The literature shows that although different forms of relapse to seeking different drugs of abuse each depend on dopamine, there are distinct dopamine mechanisms for relapse. Different circuit-level mechanisms, different populations of dopamine neurons and different activity profiles within these dopamine neurons, are important for driving different forms of relapse. This diversity highlights the need to better understand when, where and how dopamine contributes to relapse behaviours.
Topics: Animals; Dopamine; Drug-Seeking Behavior; Humans; Nucleus Accumbens; Recurrence; Reward; Substance-Related Disorders; Ventral Tegmental Area
PubMed: 33486769
DOI: 10.1111/jnc.15309 -
Current Opinion in Neurobiology Apr 2018Phasic dopamine responses are thought to encode a prediction-error signal consistent with model-free reinforcement learning theories. However, a number of recent... (Review)
Review
Phasic dopamine responses are thought to encode a prediction-error signal consistent with model-free reinforcement learning theories. However, a number of recent findings highlight the influence of model-based computations on dopamine responses, and suggest that dopamine prediction errors reflect more dimensions of an expected outcome than scalar reward value. Here, we review a selection of these recent results and discuss the implications and complications of model-based predictions for computational theories of dopamine and learning.
Topics: Animals; Computer Simulation; Dopamine; Humans; Learning; Models, Neurological; Reinforcement, Psychology
PubMed: 29096115
DOI: 10.1016/j.conb.2017.10.006 -
Chemical & Pharmaceutical Bulletin 2016N-Acyldopamines are endogenous analogs of capsaicin that exhibit cannabinoid-like activities and were identified from brain extracts. Among them, N-arachidonoyldopamine...
N-Acyldopamines are endogenous analogs of capsaicin that exhibit cannabinoid-like activities and were identified from brain extracts. Among them, N-arachidonoyldopamine (AADA) and N-oleoyldopamine (ODA) were characterized as transient receptor potential vanilloid type V1 channel (TRPV1) ligands. Recently, it was shown that N-acyldopamines may possess diverse physiological roles in addition to their ligand activities. To study the multiple functions and action mechanisms of endogenous N-acyldopamines, a simple and efficient method of N-acyldopamine synthesis was investigated. The eighteen potentially endogenous N-acyldopamines and two deuterated ones, N-palmitoyl dopamine-d5 and N-stearoyl dopamine-d5, were efficiently synthesized without protective groups in CH2Cl2 under optimized conditions using propylphosphoric acid cyclic anhydride (PPACA) as a condensation agent.
Topics: Dopamine; Molecular Structure; Phosphoric Acids
PubMed: 27373649
DOI: 10.1248/cpb.c16-00162 -
Neurobiology of Learning and Memory Feb 2014Research on dopamine lies at the intersection of sophisticated theoretical and neurobiological approaches to learning and memory. Dopamine has been shown to be critical... (Review)
Review
Research on dopamine lies at the intersection of sophisticated theoretical and neurobiological approaches to learning and memory. Dopamine has been shown to be critical for many processes that drive learning and memory, including motivation, prediction error, incentive salience, memory consolidation, and response output. Theories of dopamine's function in these processes have, for the most part, been developed from behavioral approaches that examine learning mechanisms in reward-related tasks. A parallel and growing literature indicates that dopamine is involved in fear conditioning and extinction. These studies are consistent with long-standing ideas about appetitive-aversive interactions in learning theory and they speak to the general nature of cellular and molecular processes that underlie behavior. We review the behavioral and neurobiological literature showing a role for dopamine in fear conditioning and extinction. At a cellular level, we review dopamine signaling and receptor pharmacology, cellular and molecular events that follow dopamine receptor activation, and brain systems in which dopamine functions. At a behavioral level, we describe theories of learning and dopamine function that could describe the fundamental rules underlying how dopamine modulates different aspects of learning and memory processes.
Topics: Animals; Brain; Conditioning, Psychological; Dopamine; Extinction, Psychological; Fear; Humans; Learning; Mice; Rats; Reward
PubMed: 24269353
DOI: 10.1016/j.nlm.2013.11.007