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Reference.org
Postsynaptic density
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<p>The postsynaptic density (PSD) is a protein dense <i>specialization</i> attached to the <a href="/facts/Postsynaptic/M1x5rhz7">postsynaptic</a> membrane. PSDs were originally identified by <a href="/facts/Electron_microscopy/XtaBktwF">electron microscopy</a> as an electron-dense region at the membrane of a postsynaptic neuron. The PSD is in close apposition to the presynaptic <a href="/facts/Active_zone/yPrudquX">active zone</a> and ensures that receptors are in close proximity to <a href="/facts/Presynaptic/vdMRJCUn">presynaptic</a> neurotransmitter release sites. PSDs vary in size and composition among brain regions, and have been studied in great detail at <a href="/facts/Glutamatergic/IQJ5kJjG">glutamatergic</a> synapses. Hundreds of proteins have been identified in the postsynaptic density, including <a href="/facts/Glutamate_receptors/MGwpHHUA">glutamate receptors</a>, <a href="/facts/Scaffold_protein/uKnJq24r">scaffold proteins</a>, and many signaling molecules. </p>