Do GABAergic synapses have a continuous postsynaptic scaffold?

Details

The regulation of synaptic strength at γ-aminobutyric acid (GABA)-ergic synapses depends on cytoplasmic proteins dynamically capturing, retaining, and modulating GABA A-type receptors at postsynaptic sites. How these proteins are oriented and organized in the postsynaptic cytoplasm was not yet established.

To better understand these structures and how they regulate receptor populations at postsynaptic sites, researchers used electron tomography to examine GABAergic synapses in dissociated rat hippocampal cultures. They identified and selected synapses for tomography using criteria derived from the structure of immunogold-labeled GABAergic synapses.

Tomography revealed a complex postsynaptic network of filaments extending approximately 100 nm into the cytoplasm from the postsynaptic membrane. The filaments' distribution was strikingly similar to that of the immunogold label for gephyrin. The filaments connected through uniform patterns of contact, forming complexes of 2–12 filaments each. These complexes did not join into an integrated, continuous scaffold, suggesting that GABAergic postsynaptic specializations are less rigidly organized than glutamatergic postsynaptic densities.