. The action of neurotransmitters is decreased increased or not affected by agonists and is decreased increased or not affected by antagonists.

a) Evidence to prove increased action of neurotransmitters from agonists: Agonists work by binding to specific receptors on cells which stimulates the receptors, thus increasing the action of neurotransmitters. Agonists can increase the action of neurotransmitters by mimicking the endogenous neurotransmitter or by having a stronger effect than the endogenous neurotransmitter. Studies have shown that agonists can increase the release and effectiveness of neurotransmitters like dopamine, serotonin, and acetylcholine, which help regulate many bodily processes. b) Evidence to prove decreased action of neurotransmitters from antagonists: Antagonists work by binding to specific receptors on cells and blocking the action of agonists. This can decrease the action of neurotransmitters in the body. For example, studies have shown that drugs that block dopamine receptors, such as haloperidol, can decrease dopamine levels in the brain and reduce its action on neurons. Similarly, antagonists that block serotonin receptors can reduce the activity of serotonin in the brain and thereby reduce its action on neurons. d) Evidence to prove no effect of neurotransmitters from antagonists: Some antagonists may not produce an effect on neurotransmitters. For example, some compounds act as antagonists by blocking related receptors but do not directly interact with neurotransmitters. These compounds may not affect the action of neurotransmitters, as they do not directly interact with them. Other compounds may act as antagonists by blocking the reuptake of neurotransmitters from the synaptic cleft and thus increasing their action, but not directly interact with neurotransmitters. For example, SSRIs or selective serotonin reuptake inhibitors, block the reuptake of serotonin from the synaptic cleft and increase serotonin levels, but do not interact directly with serotonin.