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What are Dopaminergic Pathways?
Neurons, the cells in the brain, communicate by sending chemicals called neurotransmitters to other cells. Dopaminergic pathways are neural networks in the brain that transmit dopamine, a type of neurotransmitter. There are four major dopaminergic pathways in the brain: the nigrostriatal pathway, the mesolimbic tract, the mesocortical tract, and the tuberoinfundibular pathway.
Neurons in the brain are built like trees, with branches coming out of the cell body on all sides and a long trunk projecting away from the body. The neuron sends electrical signals down the trunk of the tree, called the axon. At the base of the axon, the neuron releases neurotransmitters, which travel across a gap called the synapse to interact with another neuron. The neurons in the dopaminergic pathways have long axons which run the entire length of the pathway.
The neurotransmitter dopamine can have a large variety of effects on the brain, depending on location and concentration. It plays a role in cognitive functions such as learning, and also regulates some reward and punishment activities. In the midbrain, especially the substantia nigra, it is involved in motion regulation.
The nigrostriatal dopaminergic pathway arises in the substantia nigra. This pathway is important in regulating movement. In Parkinson’s disease, there is less dopamine functioning in this pathway, which leads to the motor symptoms of the disease.
The mesocortical tract, another one of the dopaminergic pathways, connects the ventral tegmentum, a part of the midbrain, to the frontal lobes of the brain. This pathway regulates some emotion and motivation. In schizophrenia, this pathway may be disrupted, leading to irregularities in emotion such as flat affect.
The mesolimbic tract also begins in the midbrain, however, it travels through the limbic system of the brain. This circuit is involved in emotion, motivation, and reward. The mesolimbic tract is another one of the dopaminergic pathways disordered in schizophrenia.
The fourth of the dopaminergic pathways is the tuberoinfundibular pathway. This tract runs from the hypothalamus to the pituitary gland. At the pituitary gland, it sends signals regulating the secretion of hormones.
Antipsychotic drugs work by blocking some types of dopamine receptors in the dopaminergic pathways of the brain. This action, however, is not limited to the mesocortical and mesolimbic tracts, which are implicated in schizophrenia. When these drugs interact with the neurons in the nigrostriatal pathway, they can cause a movement disorder called tardive dyskinesia. These antipsychotic drugs can also interfere with the functioning of the tuberoinfundibular pathway.
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![Neurons communicate by sending neurotransmitters to other cells.]()
By: Vector Art DesignNeurons communicate by sending neurotransmitters to other cells. -
![A disrupted dopaminergic pathway can lead to a flat affect in those with schizophrenia.]()
By: ForgissA disrupted dopaminergic pathway can lead to a flat affect in those with schizophrenia. -
![The mesolimbic tract travels through the limbic system of the brain, and is one of the dopaminergic pathways.]()
By: Athanasia NomikouThe mesolimbic tract travels through the limbic system of the brain, and is one of the dopaminergic pathways.
Discussion Comments
I have read about the reward pathway before, and I find it very interesting. The dopamine that travels along it provides pleasure after we do things like eat a meal when we are hungry or drink water when we are thirsty.
It also responds to painkillers. They are so addictive because they affect this pathway, and we get that euphoric feeling.
The dopamine from our own brain is what provides the sensation of pleasure. The drugs just work to make it release the stuff.
I had to take pain pills after a car wreck, and I could definitely see how they could be addictive. I suddenly felt like everything in the world was wonderful, and when that feeling faded, I felt cranky and horrible.
I find it terrible that the medicine used to treat schizophrenia can cause something as traumatic as tardive dyskinesia. My brother developed this, all because his medication messed up a certain dopaminergic pathway.
While his schizophrenic symptoms went away significantly, he traded one disorder for another. Tardive dyskinesia makes you unable to control your facial movements, and your face will have muscle spasms all the time.
His tongue sticks out over and over, and he has no control over it. His cheeks will puff up, and he will make chewing motions.
I know that schizophrenia is a terrible disease, but I think that tardive dyskinesia might be equally horrible. I think that drug manufacturers should put more resources into developing drugs that won't mess up one dopaminergic pathway while fixing another.
@shell4life – It is sad that diseases affected by dopamine pathways cannot be cured. My grandmother has Parkinson's disease, and all she can do is take drugs to control her symptoms.
She shakes all the time, though sometimes it is worse than others. She can't hold her head still, and it took me a long time to convince her to come back to church, because she was embarrassed about her constant head bobbing.
She also used to play the piano, but she had to give that up. I truly wish that something other than dopamine malfunction were the cause of this, because it is heartbreaking to know that she will suffer until she dies.
Wow, it sounds like dopamine pathways in the brain have a lot to do with schizophrenia! I suppose that if yours are somehow messed up, then you will inevitably be affected.
My cousin has schizophrenia, and I knew that it had something to do with brain chemistry, but I didn't know until reading this that it was related to dopamine. I feel bad for him, because it's not his fault that he has this disorder, and he will have to be on antipsychotic drugs for the rest of his life.
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