[An electroencephalographical study on timiperone, a new antipsychotic drug]

This investigation was undertaken to analyze the EEG synchronizing effects of timiperone in cats. The effects of timiperone on the brain-stem reticular and hypothalamic activating system, diffuse and specific thalamic projection system, and caudate spindle were investigated by the electroencephalographic method. Timiperone produced a weak inhibition of EEG arousal response induced by electrical stimulation of the sciatic nerve almost without affecting that which was induced by stimulation of the mesencephalic reticular formation. Furthermore, timiperone suppressed the activation of neocortical EEG in response to stimulation of the posterior hypothalamus more selectively than that of limbic EEG. Neither the recruiting response to stimulation of the centro-median nucleus of the thalamus nor the augmenting response to stimulation of the ventro-postero-lateral nucleus of the thalamus was modified by timiperone. In addition, timiperone significantly potentiated the caudate spindle. The EEG effects of haloperidol were qualitatively similar to those of timiperone. These results indicate that the synchronizing effect of timiperone may be mediated by a suppression of an ascending reticular activating system and may influence the conscious levels and sleep-wakefulness cycle in cats.