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dendritic spine, GABAergic inhibitory interneuron, GAD65 mouse
line, spine–dendrite coupling, structural plasticity
Abstract:
The majority of γ-aminobutyric acid (GABA)ergic interneurons have
smooth dendrites with no or only few dendritic spines, but certain
types of spiny GABAergic interneurons do actually contain substantial
numbers of spines. The explanation for such spines has so far
been purely structural: They increase the dendritic surface area and
thus provide the opportunity to accommodate larger numbers of synapses.
We reasoned that there may be specific functional properties
for these spines and therefore, undertook to characterize
interneuron spines functionally. We find a remarkable similarity to
pyramidal cell spines: They receive excitatory synapses with
calcium impermeable α-amino-3-hydroxy-5-methyl-4 isoxazolepropionic
acid (AMPA) and N-methyl-D-aspartate (NMDA) receptors,
compartmentalize biochemical signals, and display activity-dependent
morphological plasticity. Nevertheless, notable differences in
spine density, neck length, and spine–dendrite coupling exist. Thus,
dendritic spines on inhibitory interneurons have a number of important
functional properties that go substantially beyond simply expanding
the dendritic surface area. It therefore seems likely that
spiny and aspiny interneurons may have very different roles in neural
circuit function and plasticity.
