Fig. 1.

Simplified architecture of excitatory and inhibitory synapses on pyramidal cells. Pre-synaptic terminals of excitatory synapses release glutamate neurotransmitters that are post-synaptically received by glutamate receptors (NMDARs and AMPARs) on dendritic spines - small membranous protrusion stemming from the dendrite. The tip of each spine contains an electrodense region called the PSD, which is comprised of cytoskeleton anchoring proteins, such as PSD-95, designed to scaffold glutamate receptors (NMDARs and AMPARs) to the spine’s surface and to dock hundreds of signaling molecules (not shown) to the underside. Inhibitory synapses are localized to the dendritic shaft. Pre-synaptic terminals release GABA to be received post-synaptically by GABARs anchored onto the post-synaptic surface by gephyrins (gephyrins also scaffold glycine receptors, which are activated by glycine neurotransmitters - not shown). Noticeably missing is the PSD. Both synapse types are structurally maintained by trans-synaptic adhesions through cell adhesion molecules.