Preclinical Model of Parkinson’s Disease Using Circuit Specific Optogenetics (P5.402)

OBJECTIVE: To test the usefulness of reversible rodent model to understand the pathophysiology of Parkinson’s disease. BACKGROUND: Selective inhibition of the nigrostriatal pathway has become possible with the advent of optogenetics, a technique that allows insertion of light sensitive opsins that modulate electrical properties of neurons in conjunction with site specific activators like the Cre-Lox system. We demonstrate here the usefulness of this method to evaluate the behavioral effects of continuous nigrostriatal inhibition. DESIGN/METHODS: In test animals (n=11), AAV2-Ef1a-mCherry-IRES-WGA-Cre was injected into the left striatum. AAV5-Ef1a-DIO-eNpHR3.0-EYFP was then injected into both the left and right substantia nigra (SN) or left SN alone. Control animals included viral vector and laser cannulae cohorts. A 532 nm laser source and a tethered fiber system that allowed optogenetic inhibition of the SN for awake behavioral assessments. The rodent behavioral battery of tests (RBBT) was performed prior to laser testing, after laser exposure, and after recovery. RESULTS: Affected forelimb usage measured using RBBT showed significant deficits upon laser inhibition of the SN. A 93[percnt] decrement (p<0.0001) in the vibrissae evoked forelimb placement test, 65[percnt] decrement (p<0.05) in the cylinder test and 90[percnt] decrease (p<0.05) in the stepping test and was functionally restored upon discontinuation of laser stimulation. Control animals did not show any deficits from laser stimulation. Histological examination showed excellent targeting of the SN and expression of Cre, eNpHR and EYPF; and positioning of the laser cannulae. CONCLUSIONS: Our data provides proof of principle that specific Cre mediated eNpHR3.0 and EYFP expression can be achieved in all left SN neurons and all interhemispheric projections from the right SN neurons that make synaptic connections to the left striatum. Future studies will focus on intermittent stimulation of the nigrostriatal pathway to test effects of endogenous dopamine levels on development of dyskinesias. Supported by: R01NS42402, R21AT001607, DIBTH0632 Disclosure: Dr. Patel has nothing to disclose. Dr. Iyer has nothing to disclose. Dr. Venkiteswaran has nothing to disclose. Dr. Handly has nothing to disclose. Dr. White has nothing to disclose. Dr. Iqbal has nothing to disclose. Dr. Sridhar has nothing to disclose. Dr. Thiagarajan has nothing to disclose. Dr. Liu has nothing to disclose. Dr. Ramakrishnan has nothing to disclose. Dr. Deisseroth has nothing to disclose. Dr. Subramanian has received personal compensation for activities with Teva, USMedWorld, UCB Pharma as a speaker board member.