Characterization of atypical antipsychotic drugs by a late decrease of striatal alpha1 spectral power in the electropharmacogram of freely moving rats.

background and purposeDrug administration modifies the balance of neurotransmitter-controlled ion channel activity and consequently the firing pattern of local neuronal populations and intracerebral field potentials. Fast Fourier Transformation of these field potentials provides an electropharmacogram depicting drug-induced changes within defined frequency ranges. The present investigation was undertaken to investigate the difference between atypical and typical antipsychotic drugs. EXPERIMENTAL APPROACH: Adult Fisher rats were implanted with 4 bipolar concentric steel electrodes using a stereotactic surgical procedure. Field potentials from four selected brain areas in freely moving rats were used to analyse the frequency content of the electropharmacogram after administration of 4 clinically used atypical antipsychotic drugs. KEY

resultsAtypical antipsychotics exerted effects similar to those reported for typical antipsychotics, on the electropharmacogram during the first hour after administration, whereas clear differences emerged during the second and third hour after dosing. During the latter period, only atypical antipsychotic drugs produced a statistically significant decrease in alpha1 and beta1 spectral power, especially within the striatum, somewhat less in the cortex. CONCLUSIONS AND IMPLICATIONS: Previous studies have attributed alpha1 frequency changes to the influence of 5-hydroxytryptamine (5-HT) and the present data are consistent with additional binding of atypical drugs to 5-HT receptors. This implies that a change in the balance between dopaminergic and 5-hydroxytryptaminergic neurotransmission (activation of both) is likely to underlie the relative lack of extrapyramidal side effects characteristic of atypical antipsychotics and also for their higher efficacy in the treatment of mood and cognition deficits in schizophrenics.