Apomorphine-induced differences in cortical and striatal EEG and their glutamatergic mediation in 6-hydroxydopamine-treated rats

In the 6-hydroxydopamine (6-OHDA) rat model of Parkinson's disease (PD), the frequency spectra of EEG in the cortex and the striatum were studied following injection of the dopamine agonist, apomorphine (APO) alone or in combination with the NMDA antagonist, MK-801. In control rats, APO produced long-lasting (similar to 1 h) suppression of alpha activity, significantly greater in the cortex than in the striatum. In 6-OHDA rats, an even larger suppressive effect was observed in the beta frequency range, again significantly more pronounced in the cortex than in the striatum. In these animals, alpha suppression was similar in cortex and striatum in the first hour after APO injection, but alpha activity level was significantly higher in the striatum than in the cortex in the second hour. Pretreatment with MK-801 in 6-OHDA rats eliminated the APO-induced difference between cortex and striatum in the beta range, inversed the effect in the alpha range, and intensified delta activity stronger in the striatum than in the cortex. Thus, frequency-dependent differences in EEG power between cortex and striatum may be involved in dopaminergic treatment of PD and, at least in part, be mediated through NMDA receptors.