Dopamine is a neurotransmitter in the brain that communicates messages between nerve cells, called neurons, and controls emotions, learning and spontaneous and voluntary movement, according to research by K. Kobayashi, published in "Brain and Development". Dopamine depletion causes pathogenesis of brain dysfunction according to research in "Science". In research published in "Acta Psychiatrica Scandinavica", scientists present an association between dopamine dysfunction and symptoms of anhedonia, apathy and dysphoria, suffered by patients with depression, drug addiction and Parkinson's disease.
Depression
Dopamine depletion can cause depression, a mood disorder characterized by excessive sadness, inability to experience pleasure, absence of enthusiasm and discontent. According to the National Institute of Mental Health, there are different types of depression that may be associated with dopamine depletion. Major depressive disorder is characterized by chronic sadness, anhedonia, apathy and dysphoria that interferes with an individual's ability to work and play. Dysthymic disorder, also called mild depression, can last two years or longer with similar yet less serve symptoms as major depressive disorder. Psychotic depression involves symptoms of major depressive disorder plus psychosis such as hallucinations and delusions. Bipolar disorder involves symptoms of extreme depressive lows and elated highs. Postpartum depression occurs after a new mother has symptoms of major depressive disorder. L-tyrosine, an amino acid, and some antidepressants can increase dopamine levels in the brain.
Drug Addition
Dopamine is associated with pleasure and euphoria. Many addictive drugs such as cocaine and amphetamines temporarily increase dopamine levels in the brain, causing the drug user to feel high. Yet scientists at Columbia University College of Physicians and Surgeons published a study in the "American Journal of Psychiatry" that found cocaine-dependent volunteers exhibit lower levels of endogenous dopamine relative to comparison subjects. Dopamine levels in the brain become depleted after the drug wears off, and users can feel sad with an inability to experience pleasure, lack of enthusiasm and discontent. According to the National Institute of Mental Health, some drug abusers can have symptoms similar to schizophrenia such as hallucinations, delusions, disorganized thinking, agitated movements and struggle to focus.
Parkinson's Disease
Dopamine depletion can cause symptoms that are associated with Parkinson's disease. Patients suffering from Parkinson's disease experience various types of movement and other types of symptoms during the progression of their condition, according to research by M.Politis published in "Movement Disorders". Early stage symptoms include slowness, tremor, stiffness, pain and loss of smell and taste. Advanced stage symptoms include mood changes, drooling, insomnia and tremor. Physicians often prescribe a combination of levodopa and carbidopa to treat the symptoms of Parkinson's disease. Levodopa is the natural precursor to dopamine production in the brain. Carbidopa reduces the side effects from levodopa such as high blood pressure, nausea and loss of appetite.
References
- "Brain and Development"; Dopamine Deficiency in Mice; Kobayashi, K.; Sep 2000
- "Science"; Selective Brain Dopamine Depletion; Shaywitz, B.A., R.D.; Jan 23 1976
- "Acta Psychiatrica Scandinavica. Supplementum"; The Role of Dopamine in Pleasure; Bressan, R.A.; 2005
- "American Journal of Psychiatry"; Lower Level of Endogenous Dopamine in Patients with Cocaine Dependence; Martinez, D.; Oct 2009
- "Movement Disorders"; Parkinson's Disease Symptoms: Patient Perspective; Politis, M.; May 14 2010
