Stimulation of Medial Prefrontal Cortex Decreases the Responsiveness of Central Amygdala Output Neurons

Gregory J. Quirk, Ekaterina Likhtik, Joe Guillaume Pelletier, Denis Paré

Journal of Neuroscience • 2003

DOI PMC

Auditory Fear Conditioning and Extinction

behavioralrat

Objective: Test the hypothesis that medial prefrontal cortex (mPFC) inhibits conditioned fear via feedforward inhibition of central amygdala (Ce) output neurons during extinction of auditory fear conditioning

Materials & Equipment Checklist

1 item

Gather these items before starting the experiment. Check off items as you prepare.

Equipment1

Extracellular recording apparatus

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Protocol Steps

Auditory fear conditioning

Rats undergo fear conditioning where a tone predicts footshock occurrence

Note: This is the initial conditioning phase before extinction

View evidence from paper

“In extinction of auditory fear conditioning, rats learn that a tone no longer predicts the occurrence of a footshock”

Extinction training

Rats learn that the tone no longer predicts footshock, establishing extinction of the conditioned fear response

Note: Extinction phase where conditioned fear is inhibited

View evidence from paper

“In extinction of auditory fear conditioning, rats learn that a tone no longer predicts the occurrence of a footshock”

Extracellular recording from central amygdala neurons

Record extracellularly from physiologically identified brainstem-projecting central nucleus neurons to measure their responsiveness

Note: Neurons must be identified as projecting to brainstem

View evidence from paper

“Recording extracellularly from physiologically identified brainstem-projecting Ce neurons, we tested the effect of mPFC prestimulation on Ce responsiveness to synaptic input”

mPFC prestimulation

Apply prestimulation to medial prefrontal cortex and measure its effect on central amygdala output neuron responsiveness

Note: Tests the hypothesis that mPFC inhibits conditioned fear via feedforward inhibition

View evidence from paper

“mPFC prestimulation dramatically reduced the responsiveness of Ce output neurons to inputs from the insular cortex and BLA”

Measure Ce neuron responsiveness to synaptic inputs

Assess responsiveness of central amygdala output neurons to inputs from insular cortex and basolateral amygdala

Note: Measure changes in responsiveness following mPFC prestimulation

View evidence from paper

“mPFC prestimulation dramatically reduced the responsiveness of Ce output neurons to inputs from the insular cortex and BLA”