D-Cycloserine

The NMDA receptora glutamate receptor key to learning and long-term memory requires a co-agonistsomething that switches a receptor on at its glycine site to open, and D-cycloserine binds that site as a partial agonist, meaning it activates the site with intermediate efficacy. At the right level of endogenous glycine this can facilitate NMDA receptor function and the synapticrelating to synapses, the connections between neurons plasticity (long-term potentiationthe strengthening of synapses that underlies learning) that underlies new learning, which is thought to help consolidate the extinction of learned fears when paired with exposure therapy. Because it is a partial agonist, its net effect depends on background co-agonist tone, and higher or repeated exposure can behave less favorably. Separately, its antibiotic action comes from interfering with bacterial cell-wall synthesis, an unrelated mechanism.