A chronic cocaine user requires increasingly larger doses to achieve the same euphoric effect. Which mechanism in the brain's reward circuitry primarily explains this tolerance?

💡 Explanation

Drug-induced tolerance often involves a reduction in receptor sensitivity or number. Downregulation of dopamine receptors occurs in the nucleus accumbens of the reward circuit because excessive cocaine use leads to chronic overstimulation, therefore the brain reduces the number of receptors to maintain homeostasis, rather than increasing inhibitory signals or affecting other neurotransmitter systems.

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