Excitatory synaptic protein expression in hippocampal neurons in co-culture. Hippocampal neurons are stained with antibodies to the pre-synaptic protein, synapsin (green) and the excitatory post-synaptic protein, PSD-95 (red). Nuclei are stained with DAPI (blue). Scale bar represents 100 μm. Inset is an example of a 50 μm segment that would be used for excitatory synapse quantification.