Postsynapsen

Postsynapsen is the cellular component of a chemical synapse that receives signals from the presynaptic neuron. It is located on the membrane of the cell that is being contacted, which is typically another neuron but can also be a muscle cell or a gland cell. The postsynaptic membrane contains a high concentration of neurotransmitter receptors that bind substances released into the synaptic cleft and translate chemical signals into electrical or biochemical responses in the target cell.

Receptors at the postsynapse are diverse. Ionotropic receptors form ligand-gated ion channels that produce rapid changes in membrane conductance, including AMPA and NMDA receptors for glutamate and GABA_A receptors for inhibitory signals. Metabotropic receptors, such as mGluRs or dopamine/serotonin GPCRs, influence intracellular signaling cascades. When receptors are activated, the postsynaptic neuron generates postsynaptic potentials—excitatory (EPSPs) or inhibitory (IPSPs)—that summate to influence action potential firing.

Synaptic strength and plasticity at the postsynapse depend on receptor density and responsiveness. Activity can trigger trafficking of receptors to and from the membrane, particularly AMPA receptors, and structural changes in the postsynaptic density, a protein-rich region containing scaffolding proteins like PSD-95. Long-term potentiation (LTP) and long-term depression (LTD) involve coordinated postsynaptic signaling and receptor remodeling, contributing to learning and memory.

Different synapse types illustrate the postsynapse across the nervous system: glutamatergic excitatory synapses in the brain, GABAergic inhibitory synapses, and the neuromuscular junction where the postsynaptic muscle fiber expresses acetylcholine receptors. Disruptions in postsynaptic signaling are linked to neurological and psychiatric conditions, highlighting the postsynapse as a central element in neural processing.