How Does Dopamine Work in the Human Body?
Dopamine's function at the most basic level is to enable signals to pass through synapses from one neuron to another. But that's the high-level view. Up closer, the networks that use dopamine are composed of vast numbers of neurons, and the effects of releasing dopamine can vary, depending upon what types of neurons are involved and which of the five different types of receptors are using the dopamine to connect the neurons. The particular role the neurons are playing can also be a factor [source: Brookshire].
Dopamine's effects depend upon which of the four pathways is used in the brain and body where it's working to facilitate communication. The first is the nigrostriatal tract, which has to do with motor control in the body. When neurons in that system stop working, it can lead to disorders such as Parkinson's.
Another is the mesocortical pathway, which runs from the ventral tegmental area to the dorsolateral frontal cortex in the brain. It's the pathway associated with planning, prioritizing, responsibility and other executive function activities.
There's also the tuberinfundibular pathway, which connects the hypothalamus and the pituitary gland, and blocks the secretion of milk in the female breast. Blocking this pathway of dopamine enables breastfeeding.
Finally, there's the mesolimbic pathway, which is connected to the brain's limbic system, which controls reward and emotion, and includes the hippocampus and the medial frontal cortex. That's the pathway that gets the most attention, since it's connected with problems such as addiction[source: Deans].
Until recently, not much was known about the precise mechanisms by which neurons use dopamine. It was thought that it mostly took place through something called volume transmission, in which dopamine spread slowly and nonspecifically across large areas of the brain, and in the process happened to make the right contacts with the certain neurons. But in 2018, Harvard University medical researchers published a paper revealing that specialized sites on those cells release dopamine in an extremely fast —think milliseconds — and precise manner to target sites [source: Jiang].
But all that probably seems ho-hum to you, so in the next section, let's get back to the role of dopamine in the brain's reward system and in pleasure.