Basal ganglia cholinergic and dopaminergic function in progressive supranuclear palsy

Area of Science:

• Neuroscience
• Neuropathology

Background:

• Progressive Supranuclear Palsy (PSP) is a neurodegenerative disease with disappointing responses to dopaminergic and cholinergic therapies, unlike Parkinson's disease (PD) and dementia with Lewy bodies (DLB).
• The underlying neurochemical reasons for this therapeutic limitation in PSP remain unclear.

Purpose of the Study:

• To quantify dopaminergic and cholinergic receptor levels in the basal ganglia of individuals with PSP compared to controls.
• To investigate the neurochemical basis for the limited efficacy of replacement therapies in PSP.

Main Methods:

• Autoradiographic measurement of dopamine transporter (DAT), dopamine D2 receptors, nicotinic alpha4beta2 receptors, and muscarinic M1 receptors.
• Analysis was performed on striatum and pallidum tissue from pathologically confirmed PSP cases (n=15) and controls (n=32).

Main Results:

• PSP brains exhibited a significant reduction in dopamine transporter and nicotinic alpha4beta2 binding in the striatum and pallidum, indicating nigrostriatal neuronal loss.
• Striatal D2 receptor binding was elevated in the caudate, while muscarinic M1 receptor binding remained unchanged in PSP cases compared to controls.

Conclusions:

• The observed loss of presynaptic dopaminergic and cholinergic markers in PSP correlates with the poor response to dopaminergic and cholinergic replacement therapies.
• The findings suggest that postsynaptic striatal projection neurons expressing D2 and M1 receptors are relatively preserved in PSP.