Increased anxiety-like behavior following circuit-specific catecholamine denervation in mice

Area of Science:

• Neuroscience
• Neurology
• Behavioral Science

Background:

• Parkinson's disease (PD) exhibits non-motor symptoms like anxiety, poorly addressed in current models.
• Catecholamines modulate anxiety via limbic regions; their loss precedes PD motor symptoms.
• Human studies show catecholaminergic neuron loss in early PD, coinciding with anxiety emergence.

Purpose of the Study:

• To investigate if early loss of catecholaminergic inputs to the amygdala causes anxiety in Parkinson's disease.
• To determine the role of specific midbrain-amygdala circuit dysfunction in PD-related anxiety.

Main Methods:

• Bilateral 6-OHDA injections into the mouse basolateral amygdala (BL) created a specific catecholaminergic denervation.
• Assessed motor function using home cage, rotarod, beam balance, and pole climbing tests.
• Evaluated anxiety-like behavior via elevated plus-maze and light-dark exploration tests.
• Measured fear responses using Pavlovian cued conditioning and passive avoidance assays.

Main Results:

• Circuit-specific lesions increased anxiety-like behavior without impacting motor function.
• Fear behaviors remained unaffected, potentially due to preserved central amygdala innervation.
• Tyrosine-hydroxylase-labeled catecholaminergic denervation was observed in BL, intercalated cell masses, and ventral hippocampus.

Conclusions:

• Loss of catecholaminergic neurotransmission in midbrain-amygdala circuits contributes to anxiety-like behavior.
• This provides evidence for neural substrates underlying pre-motor anxiety symptoms in Parkinson's disease.
• The findings offer a novel animal model for studying PD-related anxiety.