Disclaimer: There’s a bit of brain lingo here. If you and the ‘matter are cool, by all means, keep on keepin’ on. If words like pontomesencephalotegmental complex freak you out, however, might I suggest this fun neuroanatomy review?
Oh, don’t sigh. You know you like it.
Dopamine is a neurotransmitter synthesized in your brain from an essential amino acid called tyrosine. You get much of your body’s tyrosine from your diet, notably from high-protein foods like cheeses, turkey, and pumpkin seeds.
But…why are we talking about dopamine? Since it is one of our more prominent CNS neurotransmitters, dopamine is implicated in tons of neurological and psychiatric disorders. Researchers toil every day to put their paws on what exactly dopamine is doing in the brain and spinal cord. So I am sure all of them will appreciate me narrowing down thirty years of hard work into a very brief introduction to this complex and fabulous neurotransmitter, and the receptors it affects.
There are actually quite a few ways that dopamine helps you pick up baby chickens.
1) It helps you concentrate on something you want to do, like scooping up a yellow fluffball of joy.
2) It helps you recognize that picking up something fluffy is going to make you feel good.
3) It helps you control your movements so you gently pick up the baby fluffball instead of crushing it between your ruthless human paws.
4) It helps bring joy into your heart when you pick up that little baby chicken and it peeps at you.
5) It helps you remember that you might get some chick pee (bahaha!) on your hands, so you bring some hand sanitizer.
Anyway, as of NOW, we know dopamine follows a few different pathways in the brain. These tracts are lined with dopamine receptors D1 and D2 (and D3-5 but for now let me explain what I “know”, which does not include much about the other ones. Enlighten me, I beg you.). The densities of these G-protein coupled receptors vary by location, which probably determines their varied actions. Two very important receptor pathways are the mesolimbic/mesocortical tract and the nigrostriatal pathway.
The mesolimbic/mesocortical tract originates in dopaminergic neuronal bodies in the ventral tegmental area of the brain. As you may have observed from its name, it is actually two different tracts, but for now let’s just treat it as one. It feeds dopamine to the limbic system and cerebral cortex and is often referred to as the “reward pathway”. We use rewards (thank you Pavlov!) not only to learn how to get what we want, but to be able to recognize things that are harmful to us. Much research has been devoted to the role of dopamine in addictive behaviors. Additionally, an imbalance of dopamine in this pathway (especially in the prefrontal cortex) is one of the major prevailing theories of schizophrenia.
The nigrostriatal pathway originates in dopaminergic neurons in the substantia nigra. This pathway is important because it feeds dopamine to the striatum of the basal ganglia–a dense gathering of neurons that are responsible for learned automatic movements, like walking up stairs and feeding yourself. Too little dopamine (or dopamine receptors) in this pathway can cause a disrupt in the extrapyramidal tract of motor neurons in your spinal cord. The result is the rigidity and spasticity seen in Parkinson’s Disease.
*If you did not click on the links as you were reading, I urge you to do so for your own well-being.