Dopamine

Cross references:   Catecholamine     Norepinephrine     
Nucleus Accumbens Septi     Ventral Tegmental Area      
Limbic System       

Dopamine (Wiki)   
    "Dopamine (sometimes abbreviated DA) is a catecholamine neurotransmitter present in a wide variety of animals, including both vertebrates and invertebrates.  
    In the brain, this substituted phenethylamine functions as a neurotransmitter, activating the five known types of dopamine receptorsD1, D2, D3, D4, and D5—and their variants.  
    Dopamine is produced in several areas of the brain, including the substantia nigra and the ventral tegmental area.[1]  
    Dopamine is also a neurohormone released by the hypothalamus. Its main function as a hormone is to inhibit the release of prolactin from the anterior lobe of the pituitary.
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Dopamine


    "
Dopamine has many functions in the brain, including important roles in behavior and cognition, voluntary movement, motivation, punishment and reward, inhibition of prolactin production (involved in lactation and sexual gratification), sleep, mood, attention, working memory, and learning. Dopaminergic neurons (i.e., neurons whose primary neurotransmitter is dopamine) are present chiefly in the ventral tegmental area (VTA) of the midbrain, the substantia nigra pars compacta, and the arcuate nucleus of the hypothalamus.
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    "
Dopaminergic neurons form a neurotransmitter system which originates in substantia nigra pars compacta, ventral tegmental area (VTA), and hypothalamus. These project axons to large areas of the brain which are typically divided into four major pathways: This innervation explains many of the effects of activating this dopamine system. For instance, the mesolimbic pathway connects the VTA and nucleus accumbens; both are central to the brain reward system .[12]"   
    
"Dopamine is commonly associated with the reward system of the brain, providing feelings of enjoyment and reinforcement to motivate a person proactively to perform certain activities. Dopamine is released (particularly in areas such as the nucleus accumbens and prefrontal cortex) by rewarding experiences such as food, sex, drugs, and neutral stimuli that become associated with them.[21] Recent studies indicate that aggression may also stimulate the release of dopamine in this way.[22]
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1992     
Tonic inhibition of striatal dopamine transmission: effects of benzodiazepine and GABAA receptor antagonists on extracellular dopamine levels. 
http://www.ncbi.nlm.nih.gov/pubmed/1337302   
    "
At present, it is unclear whether ligands which bind at the benzodiazepine/GABA receptor complex play a tonic modulatory role with regard to striatal dopamine (DA) transmission. The present study was designed to examine the effects of Ro15-1788, a benzodiazepine (BZ) receptor antagonist, and SR 95531, a GABAA receptor antagonist, on striatal extracellular DA (DA[e]) concentrations in anesthetized and awake rats using the technique of in vivo microdialysis. Local administration of Ro15-1788 resulted in a dose-dependent increase in DA[e] in both anesthetized and awake animals. The Ro15-1788-induced increase in DA[e] was blocked by coadministration of the BZ agonist diazepam, as well as GABA. Local administration of SR 95531 also resulted in a dose-dependent alteration in striatal DA levels in both anesthetized and awake animals. The SR 95531-induced increase in DA was blocked by coadministration of GABA. The results suggest that GABA may play a tonic inhibitory role with regard to striatal DA transmission."    
    88 Related citations: 
    1 Cited by. 


1999  
Extrastriatal dopaminergic innervation of human basal ganglia.  
http://www.ncbi.nlm.nih.gov/pubmed/10413327  

    "
A tyrosine-hydroxylase immunohistochemical analysis of the brains of normal human individuals has revealed nigrostriatal axons providing collaterals that arborize in the pallidum and subthalamic nucleus.  
    These thin and varicose collaterals emerge from thick and smooth axons that course backward along the main output pathways of the basal ganglia, including the ansa lenticularis, the lenticular fasciculus and Wilson's pencils. Many of these fibers run within pallidal medullary laminae before reaching the putamen, whereas others climb along the reticular thalamic nucleus to reach the caudate nucleus. This extrastriatal innervation, which allows nigral dopaminergic neurons to directly affect the pallidum and subthalamic nucleus, may play a crucial role in the functional organization of human basal ganglia, in both health and disease."    
    12 Cited by's
http://www.ncbi.nlm.nih.gov/pubmed?linkname=pubmed_pubmed_citedin&from_uid=10413327  


2000 
Dopaminergic innervation of human basal ganglia.  
http://www.ncbi.nlm.nih.gov/pubmed/11207419
 
    "
Our data show the existence of nigrostriatal TH-ir axons that provide collaterals arborizing in the globus pallidus and subthalamic nucleus. These thin and varicose collaterals emerge from thick and smooth axons that course along the main output pathways of the basal ganglia, including the ansa lenticularis, the lenticular fasciculus and Wilson's pencils"  
    170 Similar articles


CNS Neuroscience & Therapeutics - Volume 16, Issue 3 - June 2010 - Wiley Online Library 
This is an entire issue of the journal which is available online for free and has 11 articles on dopamine.  I clearly must come back to this.     


2013
Forebrain dopamine neurons project down to a brainstem region controlling locomotion.  
http://www.ncbi.nlm.nih.gov/pubmed/23918379      
    "The contribution of dopamine (DA) to locomotor control is traditionally attributed to ascending dopaminergic projections from the substantia nigra pars compacta and the ventral tegmental area to the basal ganglia, which in turn project down to the mesencephalic locomotor region (MLR), a brainstem region controlling locomotion in vertebrates.  
    However, a dopaminergic innervation of the pedunculopontine nucleus, considered part of the MLR, was recently identified in the monkey. The origin and role of this dopaminergic input are unknown. We addressed these questions in a basal vertebrate, the lamprey.  
    Here we report a functional descending dopaminergic pathway from the posterior tuberculum (PT; homologous to the substantia nigra pars compacta and/or ventral tegmental area of mammals) to the MLR. By using triple labeling, we found that dopaminergic cells from the PT not only project an ascending pathway to the striatum, but send a descending projection to the MLR.  
    In an isolated brain preparation, PT stimulation elicited excitatory synaptic inputs into patch-clamped MLR cells, accompanied by activity in reticulospinal cells. By using voltammetry coupled with electrophysiological recordings, we demonstrate that PT stimulation evoked DA release in the MLR, together with the activation of reticulospinal cells. In a semi-intact preparation, stimulation of the PT elicited reticulospinal activity together with locomotor movements. Microinjections of a D1 antagonist in the MLR decreased the locomotor output elicited by PT stimulation, whereas injection of DA had an opposite effect.  
    It appears that this descending dopaminergic pathway has a modulatory role on MLR cells that are known to receive glutamatergic projections and promotes locomotor output. "
    106 Related citations:   
See the paper.     
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2014   9<349   
Evolutionarily conserved organization of the dopaminergic system in lamprey: SNc/VTA afferent and efferent connectivity and D2 receptor expression.   
    "
The dopaminergic system influences motor behavior, signals reward and novelty, and is an essential component of the basal ganglia in all vertebrates including the lamprey, one of the phylogenetically oldest vertebrates.  
    The intrinsic organization and function of the lamprey basal ganglia is highly conserved. For instance, the direct and indirect pathways are modulated through dopamine D1 and D2 receptors in lamprey and in mammals. The nucleus of the tuberculum posterior, a homologue of the substantia nigra pars compacta (SNc)/ventral tegmental area (VTA) is present in lamprey, but only scarce data exist about its connectivity. Likewise, the D2 receptor is expressed in the striatum, but little is known about its localization in other brain areas. We used in situ hybridization and tracer injections, both in combination with tyrosine hydroxylase immunohistochemistry, to characterize the SNc/VTA efferent and afferent connectivity, and to relate its projection pattern with D2 receptor expression in particular. We show that most features of the dopaminergic system are highly conserved. As in mammals, the direct pallial (cortex in mammals) input and the basal ganglia connectivity with the SNc/VTA are present as part of the evaluation system, as well as input from the tectum as the evolutionary basis for salience/novelty detection. Moreover, the SNc/VTA receives sensory information from the olfactory bulbs, optic tectum, octavolateral area, and dorsal column nucleus, and it innervates, apart from the nigrostriatal pathway, several motor-related areas. This suggests that the dopaminergic system also contributes to the control of different motor centers at the brainstem level."  
 




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