Role of caloric vestibular stimulation in improvement of motor symptoms and inhibition of neuronal degeneration in rotenone model of Parkinson's disease - An experimental study.

Objective: Parkinson's disease (PD) is a progressive neurodegenerative disorder. In order to explore a noninvasive treatment of PD, in the current study the authors evaluated the neuroprotective efficacy of caloric vestibular stimulation (CVS) using the rotenone-induced rat model of PD. The rotenone models of PD are gaining attention due to high reproducibility. It is also considered to be an improved model to exhibit the pathogenesis of PD and test the neuroprotective effect of various therapeutic interventions.

Materials and methods: Rotenone was i.p. injected (3 mg/kg body weight) to male Wistar albino rats for 21 days to induce PD. As PD is chronic and progressive in nature, the efficacy of chronic CVS intervention was evaluated for 30 days after inducing PD in rats. Motor symptoms were evaluated by assessing locomotor activity in actophotometer, whereas movement analysis was done using Ludolph test and motor coordination was evaluated using rotarod apparatus. The neurochemical and neuropathological changes were also observed in the corpus striatum of rats.

Results: Rotenone administration showed decreased locomotor activity, motor coordination and general movement associated with significant (P < 0.05) reduction in dopamine content in the corpus striatum. The immunohistochemical analysis revealed a marked decrease in tyrosine hydroxylase (TH) immunoreactivity in striatal neurons indicating the significant loss of dopaminergic neurons in substantia nigra (SN) following rotenone injection. However, chronic treatment with CVS restored the nerve terminals in the striatum from rotenone damage. CVS treatment improved the dopaminergic system function by restoring dopamine content in the striatum. CVS also improved the motor deformities clearly suggesting the neuroprotective function.

Conclusion: The results of the present study suggested CVS to be a safe and simple neuroprotective measure against neurodegenerative changes in PD and a promising noninvasive technique to overcome the motor symptoms associated with it. The findings could be useful for further investigations and clinical applications of CVS in the treatment of PD.