Calcium-permeable AMPA receptors in different cell types of the neocortex

New research from neuroscientists at McGill University, Montreal and University College London, has shown that calcium-permeable AMPA receptors (CP-AMPARs) are differentially present at pyramidal cell (PC) inputs to Basket cells (BCs) and Martinotti cells (MCs) in neocortical level 5.

The results help to elucidate the role of CP-AMPARs in the neocortex and offer insight into the tight regulation of their expression in this region.

Calcium transients are critical to the regulation of synapse development, function and plasticity. In the hippocampus, studies have already identified CP-AMPARs presence and contribution to synaptic plasticity in early development, certain pathological conditions and during induction of long-term potentiation (LTP).

Led by Dr Jesper Sjöstrom, the team of researchers describe their results in a paper published in The Journal of Physiology. They looked at two distinct populations of neocortical inhibitory interneurons, BCs and MCs. CP-AMPA receptors were present at inputs into the BCs but not in MCs. These receptors also exhibited especially fast responses in BCs.

Their presence was identified through GluA2 immunolabelling and confirmed with electrophysiological recordings (AMPARs with an unedited GluA2 or no GluA2 subunits are calcium permeable). The electrophysiological recordings were performed using infrared Dodt contrast with a 40x objective on a customised SliceScope Pro electrophysiology rig from Scientifica.

The fast CP-AMPARs in BCs enable them to respond rapidly so that they quickly shut-down activity in neighbouring cells through inhibition. These findings add an important element to our understanding of brain function. CP-AMPARs have been associated with neurological conditions such as stroke, epilepsy and neurodegeneration. Additional work will be able to investigate the role of these receptors on disease states.

Paper reference:
Lalanne T., Oyrer J., Mancino A., Gregor E., Chung A., Huynh L., Burwell S., Maheux J., Farrant M., Sjöstrom P.J. Synapse-specific expression of calcium-permeable AMPA receptors in neocortical level 5 The Journal of Physiology [Accepted Article] (2015) doi: 10.1113/JP271394