Within the catecholamine family, dopamine is an essential neurotransmitter found in the limbic system of the brain. As the precursor to the neurohormones noradrenaline and adrenaline, dopamine is naturally increased in situations of stress and exercise. It also plays an important role in movement, sleep, pleasure, emotion and libido. Therefore, under normal circumstances, increases in dopamine are healthy responses when a person is in love, emotionally stimulated or has had a lack of sleep.
On the other hand, excessive levels of dopamine are not natural and can be quite dangerous. Harmful levels of the neurohormone result in a variety of symptoms depending on the location and cause of the increase. For instance, dopamine excesses caused by brain morbidities present with audio and visual hallucinations and addictive behaviors. While dopamine disorders that are more prevalent in the body produce an increased heart rate, flushing, heart palpitations, profuse sweating and high blood pressure.
Recreational Drugs
Addictive substances cause dependence by stimulating the mesolimbic system--or the pleasure center in the brain--through increasing the levels of dopamine. For instance, cocaine increases dopamine by blocking the reuptake or reabsorption of the neurotransmitter at the synapse. It does this by binding to the dopamine transport proteins responsible for reuptake, preventing them from binding to the neurohormone, thus causing dopamine to build up within the synapse space.
According to the University of Texas, amphetamines, especially methamphetamine, also promote the excess of dopamine. They do this by stimulating the pre-synaptic neuron to increase its production of the neurohormone. Other addictive substances that increase dopamine include nicotine and alcohol.
Medications
Pharmacological agents if utilized according to physician advice, are generally safe and effective. Yet, when they are accidentally or intentionally misused, they can result in severe problems, such as dangerous increases in dopamine. One of which is the excessive use of antidepressants known as monoamine oxidase inhibitors or MAOIs and norepinephrine and dopamine reuptake inhibitors, which are better known as NDRIs. Another class of medications that can severely offshoot dopamine levels is the anti-Parkinson's disease drugs such as Levodopa and Carbidopa.
Tumors
Pheochromocytomas are rare tumors found on the adrenal gland. Generally, these tumors secrete copious amounts of either noradrenaline or adrenaline, but there are cases where the tumors secrete excessive amounts of dopamine. The tumors that release dopamine are classified as extraadrenal paragangliomas and are extremely malignant. One of the first signs found in patients with these tumors is an unexplainably high blood pressure accompanied by a severe headache.
References
- "National Medical Series: Biochemistry," 4th ed.; Victor Davidson, Ph.D & Donald Sittman, Ph.D; 1999
- "Journal of Clinical Endocrinology & Metabolism"; Biochemical and Clinical Manifestations of Dopamine-Producing Paragangliomas: Utility of Plasma Methoxytyramine; Graeme Eisenhofer, MD & et al.; 2005
- "Blood Pressure"; Dopamine and Dopa Urinary Excretion in Patients with Pheochromocytoma--Diagnostic Implications; Wlodizimierz Januszewicz, MD & et al.; Sept 4, 2001
- "Download of Psychiatry"; Saxby Pridmore, MD; 2006
- "Harrison's Principles of Internal Medicine" 17th ed.; Anthony Fauci, MD & et al., eds.; 2008
