Psychoactive drugs alter behavior, thinking, and mood by acting on the brain. Most psychoactive drugs affect the brain's activity by altering synaptic transmission of a particular neurotransmitter(s).

Click here to learn about the normal process of Synaptic Transmission

Psychoactive drugs that facilitate a neurotransmitter's activity at the synapse are called agonists. Psychoactive drugs that interfere with a neurotransmitter's activity at the synapse are called antagonists. You will find some of the many agonist and antagonist psychoactive drug mechanisms listed below. The highlighted listings are linked to animations demonstrating the particular concept.

Agonist mechanisms:

A drug can increase the amount of neurotransmitter released from the synapse.

A drug can mimic the neurotransmitter's action on the postsynaptic receptor sites.

A drug can interfere with the inactivation of a neurotransmitter by blocking the reuptake of a neurotransmitter.

A drug can interfere with the inactivation of a neurotransmitter by interfering with the action of a destructive enzyme .

Antagonist mechanisms:

A drug can decrease the amount of neurotransmitter released from the synapse.

A drug can block the neurotransmitter's postsynaptic receptors.