Modelling Sensitization to Stimulants in Humans req reading

Modelling Sensitization to Stimulants in Humans
Study Overview

  • Title: Modelling Sensitization to Stimulants in Humans: A [11C]Raclopride/Positron Emission Tomography Study in Healthy Men

  • Authors: Isabelle Boileau, et al.

  • Published: Arch Gen Psychiatry, December 2006

Summary

Context & Objective

Sensitization, where repeated stimulant exposure increases psychomotor response and dopamine release, is observed in animals and may contribute to drug addiction or psychosis in humans. This study aimed to investigate behavioral and neurochemical sensitization in healthy men after limited amphetamine exposure.

Design & Participants

Ten healthy men (mean age: 25.8 ± 1.8 years) were administered three oral doses of amphetamine (0.3 mg/kg) on days 1, 3, and 5. Dopamine release was measured using positron emission tomography ([11C]raclopride) during initial exposure (day 1) and at 14 days and one year post-third exposure. Participants were selected for above-average novelty-seeking traits.

Key Findings

  • Initial amphetamine doses induced dopamine release in the ventral striatum, identified by reduced [11C]raclopride binding.

  • Sensitization-like Phenomenon: Both 14 days and 365 days after the third dose, participants showed a greater psychomotor response and heightened dopamine release compared to the initial dose. This dopaminergic response progressively extended to the dorsal caudate and putamen over time.

  • High novelty-seeking personality and impulsivity predicted sensitization predisposition.

  • Subjective ratings of energy, alertness, mood, and physiological measures (e.g., eye blink rate, cortisol) increased post-amphetamine.

Conclusions & Implications

Laboratory sensitization to stimulants is achievable in healthy men, leading to increased dopamine release that can persist for at least a year. This altered dopamine neurotransmission is crucial for understanding psychosis and addiction development, suggesting that careful monitoring of psychostimulant treatment effects is necessary, especially in vulnerable populations. The study highlights the role of the midbrain dopamine system in sensitization and points to interindividual variability in this process.