Ionotropic glutamate receptor, molecular model. When glutamate binds to this receptor, it opens up trans-membrane ion channels vital for the functioning of the nervous system. There are three types of iontropic glutamate receptors, all playing a part in synaptic plasticity, the process crucial to learning and memory. This is the AMPA (amino-hydroxy-methyl isoxazolepropionic acid) subtype. At top is the amino terminal domain. At centre is the ligand-binding domain. At bottom is the trans-membrane domain. The structure modelled here is based on studies of these receptors in the brown rat (Rattus norvegicus).