3 Categories of Psychoactive drugs 1. Heroin, morphine, and opium fit into the receptor sties known as opoid receptors. These are agonists , which are drugs that mimic the action of a neurotransmitter by binding to its receptors. The three neurotransmitters that are blocked are dopamine, scrotonin, and norepinephrine. Marijuana also acts as a mild hallucinogen, enhancing sensation.
Serotonin antagonist blocks the action of serotonin.
3 Categories of Neurons 1.