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Olanzapine, sold under the brand name Zyprexa among others, is an atypical antipsychotic primarily used to treat schizophrenia and bipolar disorder. [13] It is also sometimes used off-label for treatment of chemotherapy-induced nausea and vomiting [14] and as an appetite stimulant. [15]
The dopamine neurons of the dopaminergic pathways synthesize and release the neurotransmitter dopamine. [2] [3] Enzymes tyrosine hydroxylase and dopa decarboxylase are required for dopamine synthesis. [4] These enzymes are both produced in the cell bodies of dopamine neurons. Dopamine is stored in the cytoplasm and vesicles in axon terminals.
Dopamine is also synthesized in plants and most animals. In the brain, dopamine functions as a neurotransmitter—a chemical released by neurons (nerve cells) to send signals to other nerve cells. Neurotransmitters are synthesized in specific regions of the brain but affect many regions systemically.
Dopamine released at this site inhibits the secretion of prolactin from anterior pituitary gland lactotrophs by binding to dopamine receptor D2. Some antipsychotic drugs block dopamine in the tuberoinfundibular pathway, which can cause an increase in the amount of prolactin in the blood (hyperprolactinemia).
The excess dopamine resulting from inhibition of the dopamine β-hydroxylase enzyme increases unpleasant symptoms such as anxiety, higher blood pressure, and restlessness. Disulfiram is not an anticraving agent, because it does not decrease craving for drugs. Instead, positive punishment from its unpleasant effects deters drug consumption. [23]
Antipsychotic drugs such as haloperidol and chlorpromazine tend to block dopamine D 2 receptors in the dopaminergic pathways of the brain. This means that dopamine released in these pathways has less effect. Excess release of dopamine in the mesolimbic pathway has been linked to psychotic experiences. Decreased dopamine release in the ...
Uncommon adverse effects of olanzapine, occurring from 0.1–1%, include: Leukopaenia a comparatively low white blood cell (the cells that defend the body from foreign invaders) count. Neutropaenia a reduced neutrophil (the white blood cells that kill bacteria) count. Bradycardia (low heart rate)
The CBGTC loop has been implicated in many diseases. For example, in Parkinson's disease, degeneration of dopaminergic neurons leading to decreased activity of the excitatory pathway is thought to result in hypokinesia, [15] and in Huntington's disease, degeneration of GABAergic neurons driving the inhibitory pathway is thought to result in the jerky body movements. [2]