Differential Effects of Long-Term Treatment with Clozapine or Haloperidol on GABA Transporter Expression

Background: Post-mortem studies with brain samples of schizophrenic patients led revealed altered GABA-ergic markers like reduced expression of the GABA transporter GAT-1. Whether this effect is due to the pathophysiology of schizophrenia or to antipsychotic treatment has not been investigated. We therefore established an animal trial of long-term antipsychotic treatment to address this question.
Methods: A total of 33 adult male rats were investigated in three cohorts of 11 animals. One group received clozapine (45 mg/kg/day), another group haloperidol (1.5 mg/kg/day), and the third one pH-adapted water over a period of 6 months. In situ hybridization with cRNA probes specific for GABA transporters VGAT, GAT-1 and GAT-3 were performed in comparison to control animals.
Results: While GAT-1 was upregulated, VGAT expression declined in cortical and limbic brain regions, whereby haloperidol showed a greater effect than clozapine. GAT-3 expression was suppressed in parietal and temporal cortex.
Conclusions: We thus conclude that long-term antipsychotic treatment alters GABA transporter expression in rat. The upregulation of GAT-1 contrasts with the post-mortem finding of reduced GAT-1 expression in schizophrenic patients. Our results facilitate the distinction between disease dependent changes of GABAergic markers and medication effects.

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