In the study, the patients wore the patch -- which administers dopamine-like drugs -- for 30 hours.

CNN: New patch may control Parkinson's symptoms better - Sept. 3, 1996

It was apropos that I came home to find the iCrazy cover story on Newsweek, stating that the Internet and social media create an addiction-like dopamine response.

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The urge to drink or take drugs is, neurochemically speaking, linked to endorphins (natural morphine-like molecules) or dopamine, a neurotransmitter that is involved in bits of the brain that control reward behaviour.

ECONOMIST: New drugs for old habits

It is thought that a build up of chemicals like dopamine suppresses the activity of the brain's natural painkillers - the endogenous opioids.

BBC: Gene controls pain threshold

Yawning can be triggered by the hormone oxytocin which is released in the brain during empathetic actions like touching, kissing or cooperating, and which triggers a release of dopamine, a feel-good neurochemical.

WSJ: Matt Ridley on Why You Just Yawned | Mind & Matter

Blocking D2 reduced dopamine levels and relieved hallucinations, but it also crippled a patient's muscles and produced deadening, zombie-like effects.

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