We used electrical and optical (2-photon calcium imaging) recording in cortical pyramidal neurons and computational modeling to show that low affinity GABAARs containing an a5 subunit mediate a tonic hyperpolarization of the dendritic membrane potential, resulting in deinactivation of voltage-gated calcium channels and a paradoxical boosting of action potential-evoked calcium influx.
Experimental motivation: Blocking the GABAA receptors (GABAAR) in slices leads to suppressed calcium signals in dendrites during bAPs in mouse layer 2/3 pyramidal cells. Blocking the T-type calcium channels nearly eliminates these calcium signals. When tonic GABAAR's are blocked, the resulting slight depolarization of the dendrite plasma membrane is enough to inactivate the T-type calcium channels leading to the reduced calcium signals during bAPs.
Model Type: Neuron or other electrically excitable cell
Region(s) or Organism(s): Mouse; Neocortex
Cell Type(s): Neocortex L2/3 pyramidal GLU cell
Currents: I K; I K,leak; I L high threshold; I Na,t; I T low threshold
Receptors: GabaA
Genes:
Transmitters:
Model Concept(s): Action Potentials; Calcium dynamics; Detailed Neuronal Models; Ion Channel Kinetics
Simulation Environment: NEURON; Python
References: