Brain state-dependent alterations of corticostriatal synchronized oscillations in awake and anesthetized parkinsonian rats.

ABSTRACT

The exaggerated beta synchronized oscillation in the cortico-basal ganglia circuit is a hallmark of disease-specific motor symptoms in Parkinson's disease (PD). The functional connectivity between the cortex and basal ganglia was influenced by anesthesia. However, the correlation between anesthesia-dependent brain states and the alterations of synchronized network oscillations remains unclear. In this study, local field potentials (LFPs) were simultaneously recorded in the motor cortex and striatum of dopamine-intact and dopamine-depleted hemiparkinsonian rats. Levodopa and three anesthetics (urethane, pentobarbital, and isoflurane) were utilized to assess the changes in neural activity under different brain states. Enhanced high beta (25-40 Hz) oscillations and coherence between the cortex and striatum were found under the wakefulness in 6-OHDA-lesioned rats. Urethane-anesthetized rats exhibited both the activated state and slow wave activity intermittently, while the enhanced synchronized low beta oscillations between the cortex and striatum were observed only during the activated state, which exhibiting a pattern of activity analogous to those observed during the awake state. Notably, urethane significantly reduced the beta peak frequency during the activated state compared to wakefulness in 6-OHDA-lesioned rats. Although both pentobarbital and isoflurane commonly reduced beta oscillations and coherence between the cortex and striatum in 6-OHDA-lesioned rats, they exhibited the distinct influence over the alpha band activity. In addition, isoflurane regulated the burst suppression in a dose-dependent manner. Our data support that synchronized high beta oscillations are directly related to the motor symptoms of PD. Anesthesia regimes influence the excessive synchronized oscillations between the cortex and striatum in a brain state-dependent manner.