postsynaptically

Postsynaptically is an adverb used in neuroscience to indicate that a process occurs on the postsynaptic side of a chemical synapse—the neuron that receives a signal. At a synapse, neurotransmitter released from the presynaptic terminal crosses the synaptic cleft and binds to receptors on the postsynaptic membrane, and the resulting effects are described as postsynaptic.

Postsynaptic receptors can be ionotropic (ligand-gated ion channels) or metabotropic (G protein-coupled receptors). Activation leads to ion flux or intracellular signaling cascades, producing changes in membrane potential called excitatory postsynaptic potentials or inhibitory postsynaptic potentials. Postsynaptic responses can be fast and transient or slower and longer-lasting depending on receptor type and signaling pathways.

In synaptic plasticity, postsynaptically expressed changes include receptor trafficking to the membrane, phosphorylation of receptors, and structural changes in dendritic spines, contributing to long-term potentiation or depression.

The term is used to distinguish from presynaptically mediated effects, such as neurotransmitter release probability or presynaptic receptor modulation. In scientific descriptions, if an effect is said to be postsynaptically mediated, it means the observed outcome arises from events on the postsynaptic cell.