Fig 1: Characteristics of DIV 14 pure rat cortical neuron cultures. Panel A. Phase contrast image of cultures show abundant phase bright cell bodies with an extensive mat of interstitial neurites. Calibration bar = 85 microns. Panel B. A single confocal slice of cultures immunostained for MAP2 (green) and Piccolo (red); nuclei stained with Hoechst 33342. The merge of individual panels shows abundant pre-synaptic elements opposed to dendrites. Calibration bar = 25 microns Panel C. Western blot of cultures reveals evidence for excitatory (e.g., glutamate ionotropic receptor NMDA type subunit 1, Grin1; glutamate ionotropic receptor AMPA type subunit 1, Gria1; synapse associated protein of 97 kDa, SAP97) and inhibitor synapses (e.g., glutamate decarboxylase 67 kDa, GAD67) in cultures of neurons but not astrocytes (S100 calcium binding protein B, S100beta; glial fibrillary acidic protein, GFAP). Loading control was glyceraldehyde-3-phosphate dehydrogenase (GAPDH) when studying GFAP and actin for all the remaining proteins.