Effects of subthalamic deep brain stimulation on blink abnormalities of 6-OHDA lesioned rats

Abstract

Parkinson's disease (PD) patients and the 6-hydroxydopamine (6-OHDA) lesioned rat model share blink abnormalities. In view of the evolutionarily conserved organization of blinking, characterization of blink reflex circuits in rodents may elucidate the neural mechanisms of PD reflex abnormalities. We examine the extent of this shared pattern of blink abnormalities by measuring blink reflex excitability, blink reflex plasticity, and spontaneous blinking in 6-OHDA lesioned rats. We also investigate whether 130-Hz subthalamic nucleus deep brain stimulation (STN DBS) affects blink abnormalities, as it does in PD patients. Like PD patients, 6-OHDA-lesioned rats exhibit reflex blink hyperexcitability, impaired blink plasticity, and a reduced spontaneous blink rate. At 130 Hz, but not 16 Hz, STN DBS eliminates reflex blink hyperexcitability and restores both short- and long-term blink plasticity. Replicating its lack of effect in PD patients, 130-Hz STN DBS does not reinstate a normal temporal pattern or rate to spontaneous blinking in 6-OHDA lesioned rats. These data show that the 6-OHDA lesioned rat is an ideal model system for investigating the neural bases of reflex abnormalities in PD and highlight the complexity of PD's effects on motor control, by showing that dopamine depletion does not affect all blink systems via the same neural mechanisms.