An NMDAR positive and negative allosteric modulator series share a binding site and are interconverted by methyl groups

The neurons in the brain form networks that can change in response to experience, causing new connections to form between certain neurons and breaking the connections between others. This remodeling process underlies learning and memory. However, in certain neurological disorders, such as schizophrenia and epilepsy, these networks are disrupted and no longer work correctly. A receptor protein called the NMDA receptor plays an important role in reshaping the networks of neurons. Chemicals called neurotransmitters that are released by one neuron bind to and activate NMDA receptors on a neighbouring neuron to communicate with it. This activation encourages new connections to form between neurons. Drugs that alter the activity of the NMDA receptor could potentially act as treatments for neurological conditions that disrupt how the networks of neurons work. However, few have been approved for use in patients because most of the potential drug compounds investigated so far produce severe side effects. Perszyk et al. have now identified a new group of compounds that can potentially alter the activity of NMDA receptors without fully blocking the response, potentially eliminating the unwanted side effects. The compounds were tested on frog egg cells and human embryonic kidney cells that had been engineered to produce NMDA receptors. Small changes to the chemical structure of these compounds could switch their effect from increasing to decreasing the activity of the receptor. The compounds only interact with active receptors that have a neurotransmitter bound to them, and compete with each other to bind to the receptors. Perszyk et al. also found that some compounds behaved differently depending on how active the NMDA receptor was. These compounds could potentially be used to sense the activity in a network of neurons, which opens up new options for treating neurological conditions that affect the networks. Further experiments are now required to see how these compounds affect the activity of NMDA receptors in neurons and living animals. The range of effects produced by the compounds studied by Perszyk et al. suggests that other related compounds may have different effects on receptor activity. Future work could investigate the properties of these compounds to see if they could treat a different set of neurological disorders.