By supercooling a molecule on the surface of brain cells down to about minus 180 degrees Celsius — nearly twice as cold as the coldest places in Antarctica — scientists at Johns Hopkins Medicine say they have determined how a widely used epilepsy drug works to dampen the excitability of brain cells and help to control, although not cure, seizures.

The research identifies critical connections between activity of the epilepsy drug perampanel and the resulting movements of the AMPA receptor, a brain cell surface molecule. The researchers say their findings, published in Nature Structural & Molecular Biology, could eventually help with designing new drugs that target the receptor to treat other neurological conditions such as Alzheimer’s disease, schizophrenia, learning disabilities, glioblastoma and chronic pain.

The AMPA receptor plays a critical role for glutamate, one of the brain’s most abundant neurotransmitters, which activates neurons by connecting with a protein on the cell surface (AMPA) in a Pac-Man-like connection, in which AMPA receptors engulf glutamate. Up to four glutamate molecules can bind to a single AMPA receptor. The connection enables a flood of ions to enter the neuron and activate it.

“AMPA receptors and glutamate are necessary for most aspects of life, including the processes of learning, memory and encoding experiences. Most neurological diseases trace back in some way to AMPA receptors and glutamate,” says Edward Twomey, assistant professor of biophysics and biophysical chemistry. He was approached by neuroscientist Richard Huganir, who has been studying AMPA receptors for 40 years, to collaborate on research to better understand the receptors’ structure and their glutamate binding process.

For the study, the researchers analyzed millions of images of AMPA receptors in brain cells from mice and rat models, and their interaction with the originally discovered version of the perampanel drug. They looked at the drug’s binding with and without glutamate. They also performed electrical recordings of the ion flow and physiology studies in mice to complement the images gathered through cryo-electron microscopy (cryoEM) by postdoctoral fellow W. Dylan Hale.

Next, the researchers used artificial intelligence and machine learning tools to average and combine the cryoEM images into a 3-D reconstruction of the receptor. The team found that two of the four glutamate binding positions are the most important in the drug’s ability to block the ion flow.