Non‐Apoptotic Caspase‐3 Activation Mediates Early Synaptic Dysfunction of Indirect Pathway Neurons in the Parkinsonian Striatum

Non‐apoptotic caspase‐3 activation is critically involved in dendritic spine loss and synaptic dysfunction in Alzheimer’s disease. It is, however, not known whether caspase‐3 plays similar roles in other pathologies. Using a mouse model of clinically manifest Parkinson’s disease, we provide the first evidence that caspase‐3 is transiently activated in the striatum shortly after the degeneration of nigrostriatal dopaminergic projections. This caspase‐3 activation concurs with a rapid loss of dendritic spines and deficits in synaptic long‐term depression (LTD) in striatal projection neurons forming the indirect pathway. Interestingly, systemic treatment with a caspase inhibitor prevents both the spine pruning and the deficit of indirect pathway LTD without interfering with the ongoing dopaminergic degeneration. Taken together, our data identify transient and non‐apoptotic caspase activation as a critical event in the early plastic changes of indirect pathway neurons following dopamine denervation.