A putative animal model of the "prodromal" state of schizophrenia.

BACKGROUND: There is growing interest in detecting and treating schizophrenia during the "prodrome," before the symptoms are fully manifested. The objective of this study was to develop a putative model of the prodrome and study the effects of medications on it. METHODS: Rats were treated with different regimens of amphetamine to produce full sensitization (full syndrome) and partial sensitization (to model the prodromal state) and were then treated with typical and atypical antipsychotics and a D1 antagonist to mimic early intervention. After several weeks of withdrawal, locomotor activity in response to amphetamine and behavioral deficits (prepulse inhibition [PPI] and latent inhibition [LI]) were examined. RESULTS: Animals that received the full sensitization showed significant increase in locomotor activity and a disruption in both PPI and LI. Animals treated with a partial regimen showed only a muted phenotype. The animals that received "early intervention" did not show progression from the prodromal to the full-blown phenotype. CONCLUSIONS: The partial regimen of amphetamine injections provided a modified phenotype that could be regarded as a representative of the "prodromal" state. Early intervention, instituted once the prodromal state was already developed, prevented further progression into the full phenotype analogous to schizophrenia.