Calcium signalling in medial intercalated cell dendrites and spines

Area of Science:

• Neuroscience
• Cellular Signaling

Background:

• The amygdala is crucial for fear conditioning and extinction.
• Medial intercalated (mITC) neurons, GABAergic cells in the amygdala, control central amygdala output and are implicated in fear and extinction.
• Synaptic plasticity in basolateral amygdala (BLA) to mITC cell inputs involves NMDA receptor-dependent mechanisms and calcium signaling.

Purpose of the Study:

• To investigate the electrical and calcium signaling properties of mITC neurons.
• To elucidate the mechanisms of action potential back-propagation and synaptic calcium transients in mITC neurons.

Main Methods:

• Whole-cell patch clamp recordings in acute brain slices.
• Two-photon calcium imaging in GAD67-eGFP mice.
• Electrophysiological analysis of action potential back-propagation and synaptic responses.

Main Results:

• Action potentials back-propagate into mITC dendrites but attenuate with distance due to potassium channels.
• AMPA receptors at glutamatergic synapses exhibit both linear and rectifying current-voltage (I-V) relationships, suggesting GluA2-lacking receptors.
• NMDA receptors at these synapses are likely tri-heteromeric (GluN1/GluN2A/GluN2B) and mediate the majority of spine calcium entry.
• Synaptic stimulation leads to localized calcium signals within spines, not invading neighboring spines.

Conclusions:

• Calcium signaling in mITC neurons is tightly regulated and functions as a local signal.
• The properties of ionotropic glutamate receptors and action potential propagation influence calcium dynamics in these neurons.