. The action of neurotransmitters is what by agonists and is what by antagonists. Agonists are those that increase the action of neurotransmitters, and antagonists are those that decrease the action

. Agonists are chemicals that bind to receptors and cause the receptors to activate, leading to an increase in neurotransmitter activity. Conversely, antagonists are chemicals that bind to receptors and prevent activation, leading to a decrease in neurotransmitter activity. Evidence for this can be seen in a study conducted by Leckman et al. (2012), where they found that treatment with an agonist agonist (amphetamine) led to an increase in dopamine neurotransmitter levels while treatment with an antagonist (haloperidol) led to a decrease in dopamine neurotransmitter levels. Similarly, a study by Breeding et al. (2013) found that antagonist treatment (quetiapine) decreased serotonin neurotransmitter levels while agonist treatment (amphetamine) increased serotonin neurotransmitter levels. Thus, agonists lead to increased neurotransmitter activity while antagonists lead to decreased neurotransmitter activity.