Selective suppression of plasticity in amygdala inputs from temporal association cortex by the external capsule

Area of Science:

• Neuroscience
• Synaptic Plasticity
• Amygdala Function

Background:

• GABAergic neurons in the external capsule (EC) regulate lateral amygdala (LA) activity.
• The precise role of EC in modulating synaptic plasticity of specific cortical inputs to the LA is not well understood.
• Intermingled axonal fibers from different cortical areas complicate selective pathway analysis.

Purpose of the Study:

• To investigate the pathway-specific effects of EC on synaptic transmission and plasticity in the LA.
• To elucidate the role of GABAergic inhibition from EC in modulating long-term potentiation (LTP) in distinct amygdala input pathways.

Main Methods:

• Selective optogenetic activation of temporal association cortex (TeA) and anterior cingulate cortex (ACC) inputs to the LA using channelrhodopsin-2.
• Assessment of LTP in TeA-LA and ACC-LA pathways under conditions of EC transection or GABA(A) receptor blockade.
• Analysis of inhibitory and excitatory responses following EC transection.

Main Results:

• LTP in the TeA-LA pathway (which involves EC) was facilitated by EC transection or GABA(A) receptor blockade.
• LTP in the ACC-LA pathway (bypassing EC) was independent of GABA(A) receptor-mediated transmission.
• EC transection shifted the TeA-LA pathway balance towards excitation without affecting the ACC-LA pathway.

Conclusions:

• The external capsule exerts pathway-specific suppression of amygdala plasticity.
• GABAergic inhibition from EC plays a critical role in regulating plasticity in specific amygdala input pathways.
• These findings highlight the differential modulation of LA circuits by distinct cortical inputs.