Aquaporin-4, also known as AQP4, is a water channel protein, belonging to the aquaporin family of integral membrane proteins that conduct water through the cell membrane. In the CNS, AQP4 is the most prevalent aquaporin channel, specifically located at the perimicrovessel astrocyte foot processes, glia limitans, and ependyma. Aquaporin-4’s overall function is to provide fast water transportation as well as maintain homeostatic balance within the central nervous system. Other systems are also regulated by AQP4. AQP4 helps odorant molecules bind to target receptors and binding proteins within olfactory epithelium, and also is essential in the formation of memory as well as synaptic plasticity.