Question

fill in the blank question
opium and its natural derivatives (morphine and heroin) affects synapses in the brain that use
as their neurotransmitter.

Explanation:

Opium and its derivatives like morphine and heroin interact with brain synapses that utilize endorphins as the neurotransmitter. Endorphins are involved in pain relief and mood regulation, and these drugs mimic or affect the activity at synapses with endorphin neurotransmission.

Answer:

endorphin