Question

morphine and heroin duplicate the action of -------. endorphins lsd alcohol cigarettes

Explanation:

Morphine and heroin are opiates that mimic the action of endorphins, which are natural - occurring neurotransmitters in the body that relieve pain and produce feelings of well - being. LSD is a hallucinogen, alcohol is a depressant, and cigarettes contain nicotine which is a stimulant.

Answer:

endorphins