LSD effects serotonergic receptors. Category Where found. Strychnine, which causes death via convulsions, is a glycine antagonist. Category Where found. Heroin and percodan are opiod agonists.
Naloxone is an antagonist used to treat opiate intoxication.
Endorphins were discovered by accident. Since it seemed unlikely that there would be brain sites specific to chemicals found in the sap of flowers which grow in Asia, this pointed toward naturally occurring neurotransmitters chemically similar to the opiates . CO is less well understood. Involved in control of muscles in intestinal walls, dilates blood vessels in active brain areas and dilates blood vessels that produce penile erections.