Opioid withdrawal physiology — MRCPsych Paper A MCQ

Instant feedback + full explanation. One question, done properly.

ModerateNeurophysiology and neurochemistryOpioid withdrawal physiologyMRCPsych Paper A

A 28-year-old man stops heavy heroin use and develops yawning, lacrimation, diarrhoea, piloerection and muscle aches. Which neurotransmitter/receptor is most involved?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: E — Mu-opioid receptors

Mu-opioid receptors is best because opioid withdrawal reflects neuroadaptation after chronic mu-opioid receptor stimulation and abrupt cessation. The distractors are plausible near misses but do not fit the discriminator: Dopamine D4 receptors lacks the main clinical pattern, GABA-B receptors suggests another pathway, Serotonin 5-HT2C receptors points to a different syndrome, and Nicotinic ganglionic receptors is not supported by the vignette. Neurochemistry questions commonly test a receptor, pathway or physiological signal embedded in a clinical vignette.

Reference: RCPsych Paper A syllabus; Seminars in Psychiatry; Stahl's Essential Psychopharmacology