The Influence of Stress on Dopamine Levels
In the quest to survive, every living organism is equipped with the armor to withstand the impacts of stress. The African savanna leaves the zebra in an anxiety-ridden position of vulnerability to predators. Stress may can be as basic as the lack of food, habitat, or reproductive success. Humans are especially aware of the impacts of stress due to the nature of todayâs contemporary lifestyle. Too many daily demands can give a person anything from insomnia to indigestion to depression. Every person is equipped to naturally deal with large amounts of stress, but when these amounts exceed what the body can handle, discomfort is considerable.
Besides the qualitative approach to coping with stress, what bodily mechanisms are responsible for dealing with anxiety? The nervous system is almost solely credited with this task. The complex interaction system between billions of individual neurons facilitates large number of behaviors that result due to inputs originating inside and outside the organism. Spaces between neighboring neurons are called synapses, and one way in which they communicate is by sending chemical signals called neurotransmitters across the presynaptic membrane to the postsynaptic membrane. Years of nervous system research have determined that stress activates the neurotransmitter, dopamine.
The functions of dopamine are numerous, but in general it inhibits transmission of nerve impulses. This transmitter is found throughout the body, though mainly housed in the brainâs interior basil ganglia, in the frontal lobe of the information-processing center of the brain, or in the limbic system (1) .
Many chronic diseases result from the overproduction or underproduction of dopamine. The dopamineâs inability to move into the frontal lobe of the brain results in the inability to control fine motor movement and is familiarly called Parkinson Disease(1)  . If the flow of dopamine throughout the nervous system is not allowed to circulate as usual, then schizophrenia follows (1) .
Now that the extreme abnormalities of dopamine have been discussed, letâs look at how dopamine affects the average person who is subjected to a stressful environment.
One study maintains that the chewing behavior of mice is a response to stress, and therefore it serves as a coping device. The body responds to stress by the activation of the cerebral dopaminergic (DA) system. The study shows that when given the option of chewing, the activation of mouse DA system is drawn out (2)  In other words, when allowed to chew, a mouseâs body will have prolonged the presence of stress-managers; this coping mechanism reduces the impact of the stress.
Another study also confirms the conclusion of the aforementioned study. In this study, the levels of dopamine were reduced in Drosophila melanogaster larvae, and they all stopped exploratory behavior and died (3) . Under normal conditions, drosophila exposed to a condition of stress such as exposure to cold for a significant period of time will exhibit an increase in dopamine levels (3) . This study suggests that if an organism is exposed to external stress, dopamine levels will rise to help cope with this additional stress, and thus an organismâs survival and reproductive success is ensured due to its ability to withstand stress. This study does not mention how increased levels of dopamine contributed to certain behaviors, but other studies have shown effects of dopamine on behavior.
Thrill seeks, people who have a naturally high levels of dopamine, have the propensity to become addicted to certain drugs. High levels of dopamine unregulated by the brain protein called dopamine transporter cause the behavior of the "high" (4) . This brain protein normally cleans up dopamine that has already excited brain cells. Because dopamine controls movement, comprehension, and some social behaviors, these three behaviors manifest hyperactivity (4) . The conclusion is that addictive, novelty-seeking behaviors are the result of high levels of dopamine.As summarized by the above studies, dopamine levels are sometimes induced by stress factors. Certain dopamine levels will facilitate certain corresponding behavior. The inability of dopamine to circulate throughout the nervous system causes schizophrenia and Parkinson disease. High levels of dopamine cause drug "highs" and hyperactivity. It is obvious that dopamine levels normally should be balanced, adjusting according to the presence of stress factors to help an individual cope with life experiences.
1)http://www.llcc.cc.il.us/justice/drugs/dopamine.htm  Criminal Justice Homepage Lincoln Land Community College
2)http://www.neuroscience.wisc.edu/abstracts/519.htm The Neuroscience Training Program and the Center for Neuroscience
4)http://www.holidaylectures.org/news/bulletin/caron/caron.htm  Howard Hughes Medical Institute News
Ms. Brock, I have an inquiry in response to your essay concerning the effects of dopamine on the brain. In your essay you state the following: "If the flow of dopamine throughout the nervous system is not allowed to circulate as usual, then schizophrenia follows (1)." Isn't the dopamine theory just that, a theory? I feel that something which has not yet been proven should not be taken as fact. If I have been sorley misled, please forgive me.
"Dopamine is known for its property of controlling the flow of blood through the brain. A shortage of dopamine in the brain causes an indecisive and frozen personality. In the extreme form this is known as Parkinson’s disease. As oppose to this response, an excess of dopamine in the brain may be the immediate cause of schizophrenia. This is also how hallucinogenic drugs work, by stimulating the dopamine system." "Genome" by Matt Ridley *I hope this information is helpful =D*
Additional comments made prior to 2007
I'm concerned about several of the factual statements in your paper. The assertion that thrill seekers have high levels of dopamine is of particular interest. As you know, there is no established normal level of dopamine. If you have any research that suggests that there is now a known normal level of dopamine, please let me know as I'm in contact with several doctors from the National Institute of Mental Health. Likewise your assertion that thrill seekers have higher dopamine levels is facinating after talking via email and telephone to international experts with peer revued, published research on dopamine and brain chemistry in general. Could you please cite your research? I'm up for a good laugh! By the way how many neurotransmitters are there in your world? ... Mary Ellen Gottlieb, 29 January 2006
My 9-year-old daughter has been dealing with various tics for about two and a half to three years. I have done some of my own research and truly believe that she has "transient tic syndrome". Could these uncontrollable tics be associated with a lack of dopamine being properly transmitted through one of the 4 pathways? I really would like to understand more about dopamine and how it might be related to these ongoing tics. If you have any insight that would be helpful, I would greatly appreciate it ... Karen Roark, 30 April 2006