The EEG and behavioural changes induced by the administration of polyamines (spermine and spermidine) were studied in rabbit. Spermine and spermidine were administered at different doses (200 and 400 micrograms) into the mesencephalic ventricle (i.c.v.) both as a bolus and in constant perfusion (60 min duration). We also studied the effects of methamphetamine (MA) in a group of rabbits pretreated with spermine and spermidine 200 and 400 micrograms i.c.v. as bolus. Spermine caused a dose-related cortical synchronization associated with a partial sedation; spermidine induced cortical synchronization at a low dose without any behavioural changes while at higher dose (after perfusion) cortical desychronization with an arousal behavioural pattern occurred. The possible interaction of these substances with the mesolimbic dopaminergic system is discussed on the basis of their potential neuroleptic action.