Absolute number of three populations of interneurons and GABAergic synapses in the human hippocampus (v1.0)

Here we used unbiased stereological methods in combination with light and electron microscopic anatomical investigations in the human hippocampus. Firstly, we estimated the density and total number of three major GABAergic cell groups in all layers of the human hippocampus of 3 subjects: We examined the inhibitory parvalbumin (PV)-expressing neurons, the somatostatin (SOM)-positive inhibitory neurons and the calretinin (CR)-positive neurons. Secondly, we used 3-dimensional electron microscopy to determine the total number of GABAergic boutons and synapses in the different layers of the human hippocampus, and we also quantified those originating from PV-positive cells. These data describe densities and absolute numbers of GABAergic cells, boutons, and synapses in different sublayers and regions of the human hippocampus. These data will be essential for modeling inhibitory circuits in the human hippocampus.