DOES THE NONCOMPETITIVE NMDA RECEPTOR ANTAGONIST DIZOCILPINE (MK801) REALLY BLOCK BEHAVIORAL SENSITIZATION ASSOCIATED WITH REPEATED DRUG ADMINISTRATION

The term 'behavioural sensitization' refers to the progressively augme nted behavioural response that is produced by many drugs of abuse upon their repeated administration. From most of the available data, it ha s been concluded that co-administration of an N-methyl-D-aspartate (NM DA) receptor antagonist [such as dizocilpine (MK801)] together with th e sensitizing drug can block the development of behavioural sensitizat ion. However, the picture might not be that simple. Recent experimenta l evidence suggests that instead of blocking sensitization, co-adminis tration of dizocilpine enhances the effect of the sensitizing drug or has more complex effects on the development of sensitization. In this article, Thomas Tzschentke and Warner Schmidt present these two differ ent views and emphasize that the conclusions that can be drawn from se nsitization experiments about the effects of dizocilpine and related d rugs on behavioural plasticity crucially depend on how, when and under what conditions a test for sensitization is conducted.