Psychiatrists prescribe Seroquel for schizophrenia. The drug binds to many different receptors within the brain. In particular, it acts as a blocker or "antagonist" of serotonin receptors; it also acts as a mild antagonist at dopamine D2, histamine H1 and noradrenergic receptors. Despite the wide array of chemical systems with which it interacts, Seroquel does not bind opioid receptors. In that regard, it is not an opiate similar to heroin. However, the drug might have addictive properties.
The Mesolimbic Dopamine Reward System
According to Drs. Randy and Lori Sansone at Wright State University School of Medicine, the current theory of drug addiction posits that drugs acquire abuse potential by acting at a specific dopamine circuit within the lower front part of the brain dubbed the "mesolimbic reward system." Any substance that can increase the activity of this circuit can elicit subjective feelings of pleasure and thereby have addictive properties. On the face of this, it would seem that Seroquel's potential for recreational misuse cannot be explained by the drug's effects on dopamine. Seroquel functions as a dopamine receptor blocker--a drug that should decrease activity within the mesolimbic system. However, in a review published in the journal "Psychiatry," the physicians from Wright State note that Seroquel in fact functions as a weak antagonist relative to other antipsychotics. This opens the door for more nuanced interpretations of the drug's actions.
Histamine and Noradrenaline
Seroquel's sedative and anxiety-reducing properties could pose another mechanism that might explain the drug's liability for abuse. Histamine synthesis occurs in a central relay station of the brain called the hypothalamus. From here, histamine release influences wakefulness, anxiety, sleep and other biological rhythms. However, because Seroquel acts as a mild histamine H1 antagonist, its addictive properties probably don't stem from its effects on histamine. On the other hand, noradrenaline is a chemical that is released in response to acute and chronic stress. Because Seroquel acts as a mild noradrenergic blocker, it might reduce emotional responsiveness to everyday stressors. This might leave the drug prone to psychologically dependent use.
Benzodiazepines and Acetylcholine
Seroquel does not exert activity at benzodiazepine or acetylcholine receptors. Yet, abuse of the drug often correlates with benzodiazepine dependence. Further study will have to carefully evaluate this link.
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