SENSITIZATION TO D-AMPHETAMINE AFTER ITS REPEATED ADMINISTRATION - EVIDENCE IN EEG AND BEHAVIOR

After repeated administration of cocaine or d-amphetamine, a sensitiza tion to their behavioural effects is frequently observed instead of a tolerance. In a previous study, it was shown that a moderate dose of d -amphetamine produced a pattern of EEG power spectrum which indicated a selective activation of D-1-like dopamine receptors, whereas a large r dose induced a selective increase of power in the alpha-1 frequency band and, to a lesser degree, in the alpha-2 band, suggesting an addit ional activation of D-2-like receptors. Furthermore, it was recently f ound that under a certain dosage and schedule, cocaine could produce a shift from a D-1-characteristic to a D-2-like EEG pattern. It was now studied, if the same is true for d-amphetamine. This drug was adminis tered on 4 subsequent days (0.6 mg/kg i.p.); after an interval of 3 da ys, the same dose was administered. After repeated, but not a single a dministration, increases in the power of the alpha-1 and alpha-2 frequ ency bands were observed, suggesting a shift from activation of D-1-li ke to additional activation of D-2-like receptors. This shift was acco mpanied by a slight enhancement in stereotyped behaviour (sniffing). A fter a lower dose (0.2 mg/kg), no EEG effect could be observed, neithe r after a single nor after repeated administration.