Dopamine

02/21/2012

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Article provided with the courtesy of serotonin syndrome.
What exactly is dopamine? Just what does it do and just how does it do it? These issues have caused controversy in neuroscience for years. A brand new research from the UK can have a couple of the answers. 
The term dopamine means extremely different things to different people, from drug addiction to Parkinsons disease to a Showmanship movie dopamine is part of mainstream culture and a particular enduringly fascinating analysis topic in neuroscience. It was part of over 110,000 research forms in the last 60 years but remains a source of debate among neuroscientists. Trying to summarize the function of dopamine in a brief website post is definitely not going to be easy. I am going to leave many analysis researchers disappointed as well as some downright upset! 
Let us begin with the fundamentals. Dopamine is a neurotransmitter, like serotonin (the joy hormone - find out more what is serotonin), one of those chemicals that is responsible for transmitting signals between the nerve cells (neurons) of the mind. Few neurons actually make dopamine. Some, in a part of the brain called the substantia nigra, are the cells that die during Parkinsons disease. The functions of other folks, situated in a piece of the brain called the ventral tegmental area (VTA), are less perfectly defined and tend to be the significant source of the aforementioned debate (and also the focus of the post). Whenever dopamine neurons become triggered, they launch dopamine. 
One of the best described parts for VTA dopamine neurons is within understanding about benefits. VTA dopamine neurons become triggered when something good happens unexpectedly, including the abrupt availability of food. Many abused drugs result in the release of dopamine as well as this really is thought to lead to their addictive attributes. 
However think about bad aspects? Do they turn on dopamine neurons? It's perhaps even more important to understand when something bad is going to take place compared to some thing good; with predators or perhaps disease we frequently do not get a second chance. Is dopamine involved in understanding bad factors? Herein lies a few of the controversy surrounding dopamine. Not all neurons in the VTA make dopamine. Many research had recommended that the sudden presentation of aversive or perhaps noxious stimuli like pain caused the activation of a couple neurons in the ventral tegmental area, but have been these dopamine neurons? 
In 2004 Mark Ungless and colleagues at the College of Oxford (British) created a paper in the journal Science indicating that dopamine neurons have been universally inhibited by aversive events. They used a painstakingly detailed approach to identify those neurons which were activated or perhaps inhibited by aversive stimuli and then biochemically analysed those neurons to determine if they truly were dopamine neurons. They did discover that a couple neurons became triggered by aversive stimuli, but these neurons failed to make dopamine. 
The results had been extremely clear but were controversial. They failed to sit well with other studies on the role of dopamine, including a couple that showed that treatment with drugs which block the action of dopamine can block understanding about aversive events. Additionally, chemical measurements indicated that dopamine was introduced by animals undergoing a stressful experience. If dopamine neurons are not activated when understanding about aversive events, how is this dopamine being released? and why would definitely stopping the effects of dopamine avoid learning about aversive events? 
Ungless and co, now at the UK Health Science Analysis Council, Imperial College, London, hypothesized that the devil may be in the detail; maybe the VTA isn't a single, uniform piece of the mind however is composed of functionally different subregions. Prior to conducting their most recent research, published in the Proceedings of the National Academy of Sciences (USA) they went back and looked again at the literature about dopamine neurons in the ventral tegmental area. They seen an experimental quirk; most studies of VTA dopamine neurons, those showing that dopamine neurons aren't turned on by aversive stimuli, had been weighing responses from a same little part of the VTA, called the dorsal VTA. Just what if neurons in a different part of the VTA became activated by aversive stimuli and also released dopamine? 
To check this, they gave rats an electrical shock (not an electrocution, simply a moderate electrical shock, a great deal the same as a dog would receive from a shock raining collar). During this electric shock, they recorded the activity of neurons from the dorsal VTA and a a bit different part of the VTA called the ventral VTA. They found, such as others had previously, that neurons in the dorsal VTA were either inhibited by a particular aversive stimulus or did not respond at just about all. In comparison, those neurons in the ventral VTA became turned on by the footshock. In fact, they became extremely turned on, exhibiting a type of reaction known because "burst firing" that will be expected to produce a profound dopamine release. 
And so, that would appear to be that, issue solved! But right now there was another twist. Because I wrote earlier, one of dopamine's best known roles is within learning about benefits. Relief from a great aversive event can be considered as a advantage. The pattern of understanding exhibited by animals and people is synonymous when comparing a "real" reward (e.g, food) or relief from a great aversive stimulus (e.g; whenever a great electrical shock is turned off). Precisely what Ungless as well as co. noticed was that those neurons in the dorsal VTA, those that had been unresponsive or perhaps were inhibited by the electric shock, those neurons became transiently triggered whenever the shock was turned off. This could be consistent with their role in reward understanding whilst also partially explaining why dopamine blockers impair understanding aversive events. 
So, the story of dopamine has evolved a small but further while becoming a little but more complicated; not just about all components of the ventral tegmental region are the same! 
 
 


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