Brague, J. C. | Search bioRxiv

bioRxiv2024

Dopamine mediated plasticity preserves excitatory connections to direct pathway striatal projection neurons and motor function in a mouse model of Parkinson's disease

The cardinal symptoms of Parkinsons disease (PD) such as bradykinesia and akinesia are debilitating, and treatment options remain inadequate. The loss of nigrostriatal dopamine neurons in PD produces motor symptoms by shifting the balance of striatal output from the direct (go) to indirect (no-go) pathway in large part through changes in the excitatory connections and intrinsic excitabilities of the striatal projection neurons (SPNs). Here, we report using two different experimental models that a transient increase in striatal dopamine and enhanced D1 receptor activation, during 6-OHDA dopamine depletion, prevent the loss of mature spines and dendritic arbors on direct pathway projection neurons (dSPNs) and normal motor behavior for up to 5 months. The primary motor cortex and midline thalamic nuclei provide the major excitatory connections to SPNs. Using ChR2-assisted circuit mapping to measure inputs from motor cortex M1 to dorsolateral dSPNs, we observed a dramatic reduction in both experimental model mice and controls following dopamine depletion. Changes in the intrinsic excitabilities of SPNs were also similar to controls following dopamine depletion. Future work will examine thalamic connections to dSPNs. The findings reported here reveal previously unappreciated plasticity mechanisms within the basal ganglia that can be leveraged to treat the motor symptoms of PD.

neuroscience↗

bioRxiv2022

A striatal plasticity that supports the long-term preservation of motor function in Parkinsonian mice.

Motor deficits of Parkinsons disease (PD) such as rigidity, bradykinesia and akinesia result from a progressive loss of nigrostriatal dopamine neurons. No therapies exist that slow their degeneration and the most effective treatments for the motor symptoms: L-dopa -the precursor to dopamine, and deep brain stimulation can produce dyskinesias and are highly invasive, respectively. Hence, alternative strategies targeted to slow the progression or delay the onset of motor symptoms are still highly sought. Here we report the identification of a long-term striatal plasticity mechanism that delays for several months, the onset of motor deficits in a mouse PD model. Specifically, we show that a one-week transient daily elevation of midbrain dopamine neuron activity during depletion preserves the connectivity of direct but not indirect pathway projection neurons. The findings are consistent with the balance theory of striatal output pathways and suggest a novel approach for treating the motor symptoms of PD.

neuroscience↗