Activators and Inhibitors of the Ion Channel of the NMDA Receptor

The involvement of the glutamate-glycine activated ion channels of the NMDA receptor in various neurophysiological processes has made this ion channel the focus of intense research. The excessive release of glutamate in a variety of neuronal hypoxic conditions implicates the NMDA receptor in a number of neuropatholological states, such as stroke, chronic pain, Parkinsons disease, Alzheimers disease, ALS, and epilepsy, among others, thus making this receptor a prime drug target candidate. A variety of agents are known to be effective in opening and closing of the ion channels of this receptor, among the latter group of agents is the peptidic conantokins. Through the use of electrophysiological measurements with a number of cell types containing natural and recombinant subunits of the NMDA receptor, much knowledge is evolving regarding the mechanism of action of activators and inhibitors of the NMDA receptor ion channels. In addition, structure-function studies of the conantokins in these systems have been revealing in terms of their complimentary sites on the NMDA receptor. These relationships serve as the main focus of this review.