Nicotinic acetylcholine receptors containing homomeric pentamers of alpha subunits are one of the most abundant receptors in the nervous system. These receptors have relatively lower acetylcholine affinity but the highest Ca2+ permeability of all the nicotinic acetylcholine receptors. Homomeric alpha 7 receptors are particularly found in the cortex, hippocampus and in subcortical limbic region. These receptors are localized in the presynaptic region where they are involved in direct release of glutamate in the hippocampus, ventral tegmental area of prefrontal cortex, or in the indirect release of dopamine from striatum and prefromtal cortex, and noradrenaline from the hippocampus.