Why does the nucleus accumbens exhibit increased activity during initial drug use, but decreased sensitivity over chronic addiction?

💡 Explanation

Chronic drug use leads to downregulation of dopamine receptors in the nucleus accumbens. This decreases sensitivity to dopamine, which is why increased dopamine release no longer produces the same rewarding effect; therefore, receptor density decreases, rather than increased transporter or neurotransmitter activity, explaining the reduced response.

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