Original Investigation

Psychopharmacology

, Volume 215, Issue 2, pp 257-266

First online:

Pharmacological characterization of social isolation-induced hyperactivity

  • Katrine FabriciusAffiliated withDepartment of Synaptic Transmission2, H. Lundbeck A/S, Synaptic TransmissionFaculty of Health Sciences
  • , Lone HelboeAffiliated withDepartment of Neurodegeneration2, H. Lundbeck A/S, Neurodegeneration
  • , Anders Fink-JensenAffiliated withLaboratory of Neuropsychiatry, Mental Health Services Copenhagen, The Capital Region of Denmark, University of CopenhagenFaculty of Health Sciences
  • , Gitta WörtweinAffiliated withLaboratory of Neuropsychiatry, Mental Health Services Copenhagen, The Capital Region of Denmark, University of CopenhagenFaculty of Health Sciences
  • , Björn Steiniger-BrachAffiliated withDepartment of Synaptic Transmission2, H. Lundbeck A/S, Synaptic Transmission Email author 

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Abstract

Rationale

Social isolation (SI) of rats directly after weaning is a non-pharmacological, non-lesion animal model based on the neurodevelopmental hypothesis of schizophrenia. The model causes several neurobiological and behavioral alterations consistent with observations in schizophrenia.

Objectives

In the present study, we evaluated if isolated rats display both a pre-pulse inhibition (PPI) deficit and hyperactivity. Furthermore, the sensitivity of SI hyperactivity to antipsychotic was evaluated.

Methods

Rats were socially isolated or group-housed for 12 weeks starting on postnatal day 25. In one batch of animals, the PPI and hyperactivity response were repeatedly compared. Furthermore, we investigated the robustness of the SI-induced hyperactivity by testing close to 50 batches of socially isolated or group-housed rats and tested the sensitivity of the assay to first- and second-generation antipsychotics, haloperidol, olanzapine, and risperidone, as well as the group II selective metabotrobic glutamate receptor agonist (LY404039).

Results

Socially isolated rats showed a minor PPI deficit and a robust increase in hyperactivity compared with controls. Furthermore, SI-induced hyperactivity was selectively reversed by all antipsychotics, as well as the potential new antipsychotic, LY404039.

Conclusion

SI-induced hyperactivity was more pronounced and robust, as compared with SI-induced PPI deficits. Furthermore, SI-induced hyperactivity might be predictive for antipsychotic efficacy, as current treatment was effective in the model. Finally, using LY404039, a compound in development against schizophrenia, we have shown that the hyperactivity assay is sensitive to potential novel mechanisms of action. Thus, SI-induced hyperactivity might be a robust and novel in vivo screening assay of antipsychotic efficacy.

Keywords

Social isolation Hyperactivity Pre-pulse inhibition Antipsychotic Metabotrobic glutamate receptor mGLUR Schizophrenia