AMPA receptor

AMPA receptors are Ligand gated ion channels.The ligand (signalling molecule) they are complementary to is a Glutamate which is the main excitatory neurotransmitter in the CNS, this means there is a high proportion of these AMPA receptors on postsynaptic neurons in the brain.

When Glutamate binds to AMPA receptors it causes a conformational change and the ion channel opens allowing Na⁺ ions to flood into the postsynaptic cell. The increase in Na⁺ concentration causes depolarisation of the postsynaptic membrane generating an EPSP ( which if strong enough can go on to initiate an action potential at the axon hillock). Repetitive stimulation of these synapses in the brain can cause LTP (Long-term potentiation) , due to more Glutamate being released across the synaptic cleft binding to more AMPA receptors which leads to a higher influx of Na⁺ ions into the cell generating a stronger EPSP. This strong depolarisation of the post-synaptic member aids to the activation of NMDA receptors (along with glutamate binding) which allow Ca²⁺ ions to enter the post synaptic cell. This increase in Ca²⁺ concentration can cause new AMPA receptors to be inserted in to the post-synaptic membrane increasing the sensitivity of the post-synaptic cell to Glutamate .