Which neurotransmitter hypothesis is most strongly supported in the pathophysiology of schizophrenia?

Question

Accepted Answer

C. Dopamine hyperactivity in mesolimbic pathways and hypoactivity in mesocortical pathways. ## Dopamine Hypothesis of Schizophrenia

**Key Point:** The dopamine hypothesis remains the most robust neurochemical model of schizophrenia, supported by the mechanism of action of all antipsychotic medications and neuroimaging evidence.

### The Dopamine Dysregulation Model

**Mnemonic: MESO** — Mesolimbic (hyperactive), Mesocortical (hypoactive)

#### Mesolimbic Pathway (Hyperactive)
- **Location:** Ventral tegmental area (VTA) → nucleus accumbens and limbic structures
- **Result:** Excessive dopamine activity
- **Clinical correlate:** Positive symptoms (hallucinations, delusions, disorganized behavior)
- **Mechanism:** Overactivity in reward and emotion processing circuits

#### Mesocortical Pathway (Hypoactive)
- **Location:** VTA → prefrontal cortex (PFC)
- **Result:** Insufficient dopamine activity
- **Clinical correlate:** Negative symptoms (alogia, avolition, affective flattening) and cognitive deficits
- **Mechanism:** Reduced executive function, motivation, and emotional expression

### Evidence Supporting This Model

1. **Antipsychotic mechanism:** All antipsychotics block D~2~ dopamine receptors, reducing mesolimbic hyperactivity
2. **Amphetamine psychosis:** Stimulants (which increase dopamine) can precipitate psychotic symptoms in vulnerable individuals
3. **PET/SPECT imaging:** Shows elevated dopamine synthesis capacity in striatum of untreated patients
4. **Medication response:** Correlates with D~2~ receptor occupancy (60–70% occupancy = clinical response)

### Limitations of the Dopamine Hypothesis

- Does not fully explain negative symptoms or cognitive deficits
- Does not account for glutamate and other neurotransmitter abnormalities
- Does not explain why some patients are treatment-resistant

**Clinical Pearl:** The dopamine hypothesis explains why antipsychotics work but does not explain why schizophrenia develops. Modern understanding incorporates glutamate dysregulation, neuroinflammation, and genetic factors.

**High-Yield:** For NEET PG, remember: dopamine hyperactivity → positive symptoms; dopamine hypoactivity in PFC → negative symptoms and cognitive deficits. This is tested frequently in pharmacology and pathophysiology sections.

Answer

A. GABA hyperactivity in the prefrontal cortex

Answer

B. Serotonin deficiency in all brain regions

Answer

D. Acetylcholine excess in the basal ganglia

Which neurotransmitter hypothesis is most strongly supported in the pathophysiology of schizophrenia?

Explanation

Dopamine Hypothesis of Schizophrenia

The Dopamine Dysregulation Model

Mesolimbic Pathway (Hyperactive)

Mesocortical Pathway (Hypoactive)

Evidence Supporting This Model

Limitations of the Dopamine Hypothesis

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