Design, Synthesis, and Pharmacology of a Highly Subtype-Selective GluR1/2 Agonist, (RS)-2-Amino-3-(4-chloro-3-hydroxy-5-isoxazolyl)propionic Acid (Cl-HIBO)

On the basis of structural studies, chloro-homoibotenic acid (Cl-HIBO) was designed and synthesized. Cl-HIBO was characterized in binding and electrophysiology experiments on native and cloned subtypes of GluRs. Electrophysiological selectivities ranged from 275 to 1600 for GluR1/2 over GluR3/4. The potent AMPA receptor activity was strongly desensitizing and the neurotoxicity similar to AMPA. Thus, Cl-HIBO is the most subtype selective agonist reported to date on GluR1/2, and offers a new standard for selectively studying subtypes of AMPA receptors.