Dopamine

"Dopamine is a neurotransmitter that helps control the brain's reward and pleasure centers. Dopamine also helps regulate movement and emotional responses, and it enables us not only to see rewards, but to take action to move toward them. Dopamine deficiency results in Parkinson's Disease, and people with low dopamine activity may be more prone to addiction. The presence of a certain kind of dopamine receptor is also associated with sensation-seeking. "

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"It's what we call a monoamine, which basically means it has one amine group (the bit with the blue ball on it, the blue ball is Nitrogen) as part of its structure. There are several monoamines in the brain, including dopamine itself, norepinephrine, and epinephrine. Your brain makes dopamine all the time, out of tyrosine molecules, which are one of the 20 major amino acids that you have that make up all the different proteins and things in your body. Knowing exactly how dopamine is made is actually pretty important, scientists tweak the dopamine pathway all the time to run experiments or treat disease symptoms.....

Basically, tyrosine (your starting molecule) is transformed into another chemical called L-DOPA by an enzyme known as tyrosine hydroxylase. Tyrosine hydroxylase is the rate limiting step (basically, the slowest one) in the formation of dopamine, and so scientists often manipulate levels of tyrosine hydroxylase in animals to look at the effects on dopamine levels in the brain. You can also look at levels of tyrosine hydroxylase to see how much dopamine there is likely to be at any given time.....

Dopamine also acts as a hormone which has its main effects in the hypothalamus. Here, release of dopamine inhibits the secretion of prolactin. Prolactin is a hormone which helps regulate orgasm and the release of milk during breast feeding. I don't tend to blog about this stuff so much, though the dopaminergic regulation of the refractory period after orgasm is pretty cool....

Dopamine receptors

There are five dopamine receptors, and luckily they all act in one of two ways! Unluckily, that does not make them at all less complicated.

DA D1 and DA D5: These are known as "stimulatory receptors", meaning they stimulate the cell that they are on when they get activated by dopamine. Now, if that cell is ALSO stimulatory to further cells down the line, the net effect is stimulation, but if the cell is inhibitory to other cells down the line, the net effect can be inhibition.

DA D2, D3, and D4: These are known as "inhibitory" receptors. But remember the main effect is not always inhibitory, unless they are inhibiting a stimulatory cell. They can also inhibit an inhibitory cell, which can stop inhibition of other cells down the like and result in stimulation! Does your head hurt yet?"

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@Cedarlane