What is the role of dopamine in cocaine-induced neurologic syndromes?

Updated: Sep 01, 2018
  • Author: Lynn Barkley Burnett, MD, EdD, LLB(c); Chief Editor: Sage W Wiener, MD  more...
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Answer

Drugs that increase intrasynaptic dopamine change the density and sensitivity of dopamine receptors, with different effects on different receptor subtypes in different areas of the brain. [16] Excited delirium, cocaine-associated rhabdomyolysis (CAR), and neuroleptic malignant syndrome (NMS) share many common features that can be explained by aberrant dopaminergic function.

Long-term cocaine use decreases the density of dopamine-1 (D1) receptors throughout the striatal reward centers, but it does not affect the number of dopamine-2 (D2) receptors. Antagonism of nigrostriatal dopamine function may cause extrapyramidal motor dysfunction, including dystonic reactions, bradykinesia, akinesia, akathisia, pseudoparkinsonism, and catalepsy. Neuroleptic agents are the principal medications that cause dystonic reactions by means of their blockade of dopamine receptors in the nigrostriatal pathways. Cocaine may increase the risk of neuroleptic-induced dystonias, a problem compounded by the street marketing of substances, such as haloperidol, sold as cocaine.

Over time, continued use may result in depletion of dopamine. Therefore, cocaine may be an independent cause of dystonic reactions. Two biochemical events, dopamine receptor blockade by neuroleptics and dopamine depletion by cocaine, result in the same effect, namely, the absence of physiologic dopamine in the nigrostriatal area of the brain. These events may represent the pathophysiologic basis for cocaine-associated dystonias. Intrauterine exposure to cocaine has been suggested as a cause of dystonia in infants.


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