Postsinaptice

Postsinaptice, most commonly called postsynaptic, refers to the region of a chemical synapse that responds to neurotransmitter released from the presynaptic terminal. It comprises the postsynaptic membrane of the receiving cell, its receptors, and the associated signaling machinery that converts chemical signals into electrical or biochemical responses. In the central nervous system, the postsynaptic neuron typically contains receptors for glutamate (such as AMPA, NMDA) and GABA (such as GABA-A), as well as metabotropic receptors for other transmitters. At the neuromuscular junction, the postsynaptic membrane bears nicotinic acetylcholine receptors that trigger muscle contraction.

The postsynaptic response depends on the type of receptor activated. Ionotropic receptors form ligand-gated channels producing fast excitatory or inhibitory postsynaptic potentials, while metabotropic receptors initiate slower signaling cascades via second messengers. The postsynaptic density, a protein-rich specialization beneath the membrane, anchors receptors and signaling proteins including scaffold proteins (e.g., PSD-95) and kinases.

Electrical signals at the postsynaptic site are called postsynaptic potentials (PSPs), including excitatory (EPSP) and inhibitory (IPSP) components. Integration of multiple PSPs determines whether a postsynaptic neuron reaches threshold to fire an action potential. Plastic changes can occur at the postsynaptic side, such as receptor trafficking (e.g., insertion or removal of AMPA receptors) and modulation of signaling pathways, underlying learning and memory processes like long-term potentiation and long-term depression.

Disorders can involve postsynaptic components. Abnormal postsynaptic receptor function or density is implicated in conditions such as myasthenia gravis and various neuropsychiatric disorders, while precise receptor dysfunction can disrupt synaptic balance and network activity.