Mecanismos generadores de la actividad beta subtalámica y otras oscilaciones anómalas de los basales. Papel en la fisiopatología de la enfermedad de parkinson

Resumen

We studied the oscillatory activity from different nuclei from basal ganglia and motor cortex in both control and 6-OHDA lesioned rats as a model of Parkinson disease. We recorded local field potentials from the motor cortex, subthalamic area, caudate-putamen and substantia nigra pars reticulate in basal conditions and under pharmacological stimulation of three different drugs: apomorphine (dopaminergic agonist), haloperidol (dopaminergic antagonist) and ketamina (NMDA). 6-OHDA lesioned rats show abnormal beta activity in basal ganglia and motor cortex, which is reduced after apomorphine administration. Despite of some differences in amplitudes, apomorphine also induced two peaks of activity in the gamma range (around 45 and 85Hz) in both groups. Ketamine administration increased the power of the oscillatory activity at different frequencies. Nevertheless, the most prominent increase was observed for high frequencies, in the range of 140-160Hz. This activity also showed a high correlation with the motor activity of the animals. The most important finding in this work was the observation of changes in the fractal properties of the oscillatory activity due to pharmacological stimulation/6-OHDA lesion. The power spectrum showed an 1/f characteristic trend, resulting in an inverse linear relation between log power and log frequency. While the slope of this trend (scaling exponent) was increased by chronic (6-OHDA) or acute (haloperidol) blockage of dopaminergic system, apomorphine administration increased this value. These results suggest that not only the irruption of novel activities but also the modification of other features of the oscillatory activity could play an important role in the physiopathology of PD.