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Optostimulation of striatonigral terminals in substantia nigra induces dyskinesia that increases after L‐DOPA in a mouse model of Parkinson's disease
Author(s) -
Keifman Ettel,
RuizDeDiego Irene,
Pafundo Diego Esteban,
Paz Rodrigo Manuel,
Solís Oscar,
Murer Mario Gustavo,
Moratalla Rosario
Publication year - 2019
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/bph.14663
Subject(s) - substantia nigra , medial forebrain bundle , dyskinesia , basal ganglia , stimulation , medium spiny neuron , neuroscience , parkinson's disease , gabaergic , dopamine , deep brain stimulation , nigrostriatal pathway , direct pathway of movement , levodopa , oxidopamine , parkinsonism , medicine , striatum , psychology , dopaminergic , inhibitory postsynaptic potential , disease , central nervous system
Background and Purpose L‐DOPA‐induced dyskinesia (LID) remains a major complication of L‐DOPA therapy in Parkinson's disease. LID is believed to result from inhibition of substantia nigra reticulata (SNr) neurons by GABAergic striatal projection neurons that become supersensitive to dopamine receptor stimulation after severe nigrostriatal degeneration. Here, we asked if stimulation of direct medium spiny neuron (dMSN) GABAergic terminals at the SNr can produce a full dyskinetic state similar to that induced by L‐DOPA. Experimental Approach Adult C57BL6 mice were lesioned with 6‐hydroxydopamine in the medial forebrain bundle. Channel rhodopsin was expressed in striatonigral terminals by ipsilateral striatal injection of adeno‐associated viral particles under the CaMKII promoter. Optic fibres were implanted on the ipsilateral SNr. Optical stimulation was performed before and 24 hr after three daily doses of L‐DOPA at subthreshold and suprathreshold dyskinetic doses. We also examined the combined effect of light stimulation and an acute L‐DOPA challenge. Key Results Optostimulation of striatonigral terminals inhibited SNr neurons and induced all dyskinesia subtypes (optostimulation‐induced dyskinesia [OID]) in 6‐hydroxydopamine animals, but not in sham‐lesioned animals. Additionally, chronic L‐DOPA administration sensitised dyskinetic responses to striatonigral terminal optostimulation, as OIDs were more severe 24 hr after L‐DOPA administration. Furthermore, L‐DOPA combined with light stimulation did not result in higher dyskinesia scores than OID alone, suggesting that optostimulation has a masking effect on LID. Conclusion and Implications This work suggests that striatonigral inhibition of basal ganglia output (SNr) is a decisive mechanism mediating LID and identifies the SNr as a target for managing LID.