Schematic representation of the glutamatergic and GABAergic receptors in a CA1 pyramidal neuron. The left box represents a CA3-CA1 synapse. The CA3 axon (orange) releases glutamate from the presynaptic terminals. The postsynaptic CA1 neuron expresses three types of glutamatergic receptors: metabotropic receptor (mGluR), alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR), and N-methyl-D-aspartate receptor (NMDAR). The AMPARs are represented in their active state, as they allow Na+ to enter onto the dendritic spine. The NMDARs are represented both in the closed state (leftmost NMDAR, with the Mg2+ block seen as a red ball in the mouth of the receptor) and in the open state, when the NMDARs allow Ca2+ to enter onto the spine (notice the absence of the Mg2+ block). The right box represents a synapse between an inhibitory interneuron and the CA1 cell. The interneuron releases γ-aminobutyric acid (GABA) onto the CA1 pyramidal neuron, which expresses GABAA receptors (yellow) and GABAB receptors (gray), leading to inhibition of the target cell. The GABAA receptors are represented in the open state when they allow Cl- to enter onto the CA1 dendrite.