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Endorphins
Endogenous substances that offer pain relief and increase pleasure sensations.
Agonists
Substances that activate neurotransmitter receptors, enhancing the natural activity of neurotransmitters.
Antagonists
These are substances or muscles that counteract or oppose the function or action of another—for example, a muscle that opposes the action of another muscle or a drug that blocks receptors for neurotransmitters.
Endorphins
Neurotransmitters produced by the brain that act as natural painkillers and are also associated with feelings of pleasure and euphoria.