Mesolimbic dopamine and psychosis — MRCPsych Paper A MCQ

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EasyNeurophysiology and neurochemistryMesolimbic dopamine and psychosisMRCPsych Paper A

A 23-year-old man has auditory hallucinations and persecutory delusions that improve after treatment with a dopamine D2 receptor-blocking antipsychotic. According to the classical dopamine hypothesis of psychosis, overactivity in which pathway is associated with these positive symptoms?

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Correct answer: A — Mesolimbic dopamine pathway

The correct answer is A, the mesolimbic dopamine pathway. In the classical dopamine hypothesis, increased mesolimbic dopaminergic activity is associated with positive psychotic symptoms such as hallucinations and delusions; reducing D2-mediated signalling contributes to antipsychotic efficacy. The tuberoinfundibular pathway regulates prolactin, and its blockade can cause hyperprolactinaemia. The nigrostriatal pathway is primarily associated with motor control, with D2 blockade producing extrapyramidal adverse effects. Contemporary imaging research has implicated associative dorsal striatal dopamine dysfunction more strongly than the original mesolimbic model, which is why the stem specifies the classical hypothesis. The dorsal columns transmit vibration, proprioception and discriminative touch, while the retinohypothalamic pathway conveys light information to the suprachiasmatic nucleus for circadian entrainment.

Reference: National Institute for Health and Care Excellence. Psychosis and schizophrenia in adults: treatment and management, full guideline, section discussing the dopamine hypothesis. 2014. https://www.nice.org.uk/guidance/cg178/evidence/full-guideline-pdf-490503565