With no explanation, label text_A→text_B with either "not_related" or "related".
text_A: Dopamine is a chemical.
text_B: Dopamine -LRB- DA , contracted from 3,4-dihydroxyphenethylamine -RRB- is an organic chemical of the catecholamine and phenethylamine families that plays several important roles in the brain and body .. organic chemical. organic compound. catecholamine. catecholamine. phenethylamine. phenethylamine. brain. brain. Dopamine. Dopamine ( medication ). It is an amine synthesized by removing a carboxyl group from a molecule of its precursor chemical L-DOPA , which is synthesized in the brain and kidneys .. L-DOPA. L-DOPA. amine. amine. carboxyl group. C-terminus. precursor chemical. precursor ( chemistry ). synthesized. biosynthesis. brain. brain. Dopamine is also synthesized in plants and most animals .. synthesized. biosynthesis. Dopamine. Dopamine ( medication ). In the brain , dopamine functions as a neurotransmitter -- a chemical released by neurons -LRB- nerve cells -RRB- to send signals to other nerve cells .. brain. brain. neurotransmitter. neurotransmitter. The brain includes several distinct dopamine pathways , one of which plays a major role in reward-motivated behavior .. brain. brain. dopamine pathways. dopaminergic pathway. reward-motivated behavior. reward system. Most types of rewards increase the level of dopamine in the brain , and many addictive drugs increase dopamine neuronal activity .. brain. brain. addictive. addiction. Other brain dopamine pathways are involved in motor control and in controlling the release of various hormones .. brain. brain. dopamine pathways. dopaminergic pathway. motor control. motor system. These pathways and cell groups form a dopamine system which is neuromodulatory .. cell groups. dopaminergic cell groups. neuromodulatory. neuromodulation. Outside the central nervous system , dopamine functions primarily as a local chemical messenger .. central nervous system. central nervous system. chemical messenger. neurotransmitter. In blood vessels , it inhibits norepinephrine release and acts as a vasodilator -LRB- at normal concentrations -RRB- ; in the kidneys , it increases sodium excretion and urine output ; in the pancreas , it reduces insulin production ; in the digestive system , it reduces gastrointestinal motility and protects intestinal mucosa ; and in the immune system , it reduces the activity of lymphocytes .. norepinephrine. norepinephrine. vasodilator. vasodilator. pancreas. pancreas. gastrointestinal motility. Gastrointestinal physiology#Motility. intestinal mucosa. intestinal mucosa. lymphocytes. lymphocytes. With the exception of the blood vessels , dopamine in each of these peripheral systems is synthesized locally and exerts its effects near the cells that release it .. synthesized. biosynthesis. Several important diseases of the nervous system are associated with dysfunctions of the dopamine system , and some of the key medications used to treat them work by altering the effects of dopamine .. Parkinson 's disease , a degenerative condition causing tremor and motor impairment , is caused by a loss of dopamine-secreting neurons in an area of the midbrain called the substantia nigra .. substantia nigra. substantia nigra. midbrain. midbrain. Its metabolic precursor L-DOPA can be manufactured , and in its pure form marketed as Levodopa is the most widely used treatment for the condition .. L-DOPA. L-DOPA. There is evidence that schizophrenia involves altered levels of dopamine activity , and most antipsychotic drugs used to treat this are dopamine antagonists which reduce dopamine activity .. schizophrenia. schizophrenia. antipsychotic drugs. antipsychotic. Similar dopamine antagonist drugs are also some of the most effective anti-nausea agents .. dopamine antagonist. dopamine antagonist. anti-nausea agents. antiemetic. Restless legs syndrome and attention deficit hyperactivity disorder -LRB- ADHD -RRB- are associated with decreased dopamine activity .. Restless legs syndrome. Restless legs syndrome. attention deficit hyperactivity disorder. attention deficit hyperactivity disorder. Dopaminergic stimulants can be addictive in high doses , but some are used at lower doses to treat ADHD .. addictive. addiction. Dopaminergic. Dopaminergic. stimulants. sympathomimetic drug. Dopamine itself is available as a manufactured medication for intravenous injection  : although it can not reach the brain from the bloodstream , its peripheral effects make it useful in the treatment of heart failure or shock , especially in newborn babies .. brain. brain. Dopamine. Dopamine ( medication ). medication. pharmaceutical drug. intravenous injection. intravenous therapy. heart failure. heart failure. shock. shock ( circulatory )
related.