From use to addiction: receptor loss, hypofrontality, craving and relapse
Explains how chronic use changes the brain: fewer dopamine receptors in the nucleus accumbens, a weakened frontal lobe (hypofrontality), glutamate-driven craving, lost inhibitory control, and relapse.
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- Acute and chronic effects: up- and down-regulation — Dopamine receptor down-regulation is chronic agonism's adaptation.
- Glutamate and GABA: the brain's accelerator and brake — Craving runs through glutamate projections.
- Who becomes addicted: genes, stress and dopamine receptors — Low D2 density appears again — but which came first?
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- Treating addiction: substitution, antagonists, glutamate, vaccines — and the model's limits — Each change suggests a treatment target: receptors, glutamate, relapse.
Recorrido
Fewer dopamine receptors in the NAc
Persistent drug-driven dopamine down-regulates dopamine receptors in the nucleus accumbens. The reward system becomes desensitized to natural rewards and normal dopamine release — 'tolerance' to ordinary life.
Analogía y ejemplo resuelto
Analogía: Picture the frontal lobe as a driver and the reward circuit as the engine. Chronic use turns the engine's response to normal fuel down (so ordinary rewards barely move the car), weakens the brakes (hypofrontality), and rigs certain road signs — the drug cues — to slam the accelerator (glutamate craving).
A person abstinent from cocaine for six months walks past the corner where they used to buy and suddenly craves intensely, then relapses. Explain using course concepts.
- The corner is a conditioned drug cue — learned through associative learning.
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