Dysfunction of the midbrain angular complex can accentuate or attenuate circling behaviour in the rat

Area of Science:

• Neuroscience
• Behavioral Neuroscience
• Motor Control

Background:

• The midbrain angular complex (AC) is implicated in motor behaviors.
• Understanding the AC's precise role requires detailed behavioral analysis.

Purpose of the Study:

• To investigate the role of the midbrain angular complex (AC) in motor behavior execution in rats.
• To elucidate the AC's involvement in locomotion, exploration, and drug-induced behaviors.

Main Methods:

• Bilateral and unilateral electrolesions of the AC in rats.
• Automated holeboard apparatus for behavioral testing.
• Systemic and localized administration of apomorphine and muscimol.
• Assessment of locomotion, exploration, posture, circling, and stereotypy.

Main Results:

• Bilateral AC lesions attenuated exploration and increased locomotion, potentially by retarding habituation.
• AC lesions reinstated locomotion suppressed by apomorphine but did not affect other behaviors.
• Unilateral AC lesions induced ipsiversive circling with apomorphine and altered responses in 6-OHDA treated rats.
• Bilateral AC lesions potentiated circling to systemic apomorphine and facilitated locomotion.

Conclusions:

• The AC is not specifically involved in mediating postural asymmetry in 6-OHDA denervated rats.
• AC impairment may independently bias movement towards the affected side, reduce stereotypy, and facilitate locomotion.
• GABA-mediated synapses in the AC appear to be functionally active in motor control.