Psychiatry: basic sciences
Neurochemistry
Neurochemistry is the study of the chemical messengers in the brain, such as dopamine, serotonin, glutamate and GABA. It explains current theories of mental illness and how psychiatric medicines work.
Depth by stage, Pre-U → Consultant (details)
What is it?
Brain cells talk to each other using chemical messengers called neurotransmitters. Neurochemistry covers how these chemicals are made, released, received and broken down, and the receptors they act on.
Almost every psychiatric medicine works by changing this chemistry: antidepressants act mainly on serotonin and noradrenaline, antipsychotics block dopamine receptors, and sedatives enhance GABA. The well-known 'chemical imbalance' explanations of mental illness are simplifications of this field.
Psychiatry trainees study neurochemistry in depth for their basic sciences examinations and learn to judge the strength and limits of each neurochemical theory.
Why does a psychiatrist need it?
A psychiatrist must explain to patients how their medicine works, predict side effects from receptor profiles, and understand why some drugs interact dangerously (for example serotonin syndrome). Neurochemistry also helps the psychiatrist read research critically, since many theories of illness, such as the dopamine hypothesis of schizophrenia, are neurochemical.
What level is expected at each stage?
Scale: 1. Aware → 2. Understands → 3. Applies → 4. Masters / Teaches. What the levels mean.
- Pre-UAwareKnows from chemistry and biology that cells signal using molecules and that enzymes and receptors exist.
- Pre-clinicalUnderstandsNames the main neurotransmitters, their synthesis and receptors as part of biochemistry and pharmacology.
- ClinicalUnderstandsLinks neurotransmitters to common drugs met on the wards (opioids, benzodiazepines, antipsychotics).
- HousemanshipUnderstandsApplies this when prescribing and recognising side effects and toxicity under supervision.
- Medical officerUnderstandsExplains to patients, in simple terms, how their psychiatric medicine acts.
- Psych traineeAppliesDescribes each neurotransmitter system and the main neurochemical theories of illness, with their evidence and limits.
- Specialist / consultantAppliesUses neurochemistry to reason through complex prescribing and to critique new research and drugs.
What are the key topics?
Principles
- Synthesis, storage, release, reuptake and metabolism of neurotransmitters
- Receptor types, agonists, antagonists, partial agonists and inverse agonists
- Second messengers and intracellular signalling
- Receptor up- and down-regulation with long-term drug use
- Neuropeptides and neuromodulators
Monoamines
- Dopamine: synthesis from tyrosine, D1–D5 receptors, four main pathways
- Serotonin (5-HT): synthesis from tryptophan, key receptor subtypes, roles in mood, anxiety, sleep and appetite
- Noradrenaline: arousal, attention, stress
- Monoamine oxidase and COMT in breakdown
- Histamine and its role in sedation and weight gain
Amino acids and acetylcholine
- Glutamate and NMDA/AMPA receptors; excitotoxicity
- GABA and the GABA-A receptor; benzodiazepines and alcohol
- Acetylcholine: nicotinic and muscarinic receptors; memory and dementia treatment
- Glycine as co-agonist at NMDA receptors
Neurochemical theories of illness
- Dopamine hypothesis of schizophrenia and its revisions
- Glutamate (NMDA hypofunction) hypothesis of psychosis
- Monoamine hypothesis of depression and its limits; neuroplasticity and inflammation models
- GABA and noradrenaline in anxiety
- Reward pathways and dopamine in addiction
- Cholinergic hypothesis of Alzheimer's disease
Other systems
- Endogenous opioids and the endocannabinoid system
- Melatonin and the sleep–wake cycle
- Neurotrophic factors (e.g. BDNF)
- Inflammatory cytokines and mood (emerging evidence)
How is it learned and assessed?
- Biochemistry and pharmacology teaching in pre-clinical years
- Basic sciences teaching in psychiatry training; examined in MMed Psychiatry Part I and MRCPsych Paper A
- Journal clubs reviewing neurochemical research
- Applied in daily prescribing decisions during clinical rotations
Typical textbooks and resources
- Stahl's Essential Psychopharmacology — Stephen Stahl; illustrated neurotransmitter systems
- Basic Neurochemistry — Brady, Siegel and colleagues; detailed reference
- Oxford Textbook of Psychiatry (Shorter / New) — Oxford University Press; summary chapters on neuroscience
- Revision guides for MRCPsych Paper A — various authors
Titles are widely used examples; editions change. Use university libraries or legitimate purchases.
Common questions
Is mental illness really a 'chemical imbalance'?
That phrase is a simplification. Brain chemistry is clearly involved and medicines that change it can help, but mental illness also involves genes, brain circuits, life experiences and social circumstances. Psychiatrists learn to explain this more balanced picture.
Which neurotransmitters matter most in psychiatry?
Dopamine, serotonin, noradrenaline, glutamate, GABA and acetylcholine are the core ones. Most psychiatric medicines act on at least one of them.