Which mechanism best explains the euphoric effect associated with narcotics?

• A. Blocking GABA activity
• B. Attaching to endorphin receptors
• C. Flooding synapses with norepinephrine
• D. Increase release of acetylcholine

Answer: (B)

The euphoric effect of narcotics comes from activating the brain’s endogenous opioid system by binding to endorphin (mu-opioid) receptors. When narcotics bind to these receptors in reward-related areas, they inhibit nearby GABAergic interneurons. Since GABA normally dampens dopamine neurons, this inhibition of GABA disinhibits dopamine neurons, leading to increased dopamine release in the nucleus accumbens. That surge in dopamine creates the intense feeling of pleasure and reinforcement. The other mechanisms don’t capture this receptor-level action: narcotics don’t simply block GABA outright, and they don’t primarily flood synapses with norepinephrine or increase acetylcholine to produce the same euphoric effect.