A new positron emission tomography (PET) imaging agent could help guide and evaluate treatments for people with neurological diseases such as Alzheimer's and multiple sclerosis, according to an April 2 release from the Society of Nuclear Medicine and Molecular Imaging.   

The study, featured in the April issue of the Journal of Nuclear Medicine, explained how researchers developed the new PET radioligand, 11C-Me-NB1, for imaging GluN1/GluN2B-containing N-methyl-D-aspartate (NMDA) receptors (a class of glutamate receptor) in nerve cells. Specifically, the agent targets receptors in the brain's nerve cells responsible for learning and memory   

"For the study, 11C-Me-NB1 was used in live rats to investigate the dose and effectiveness of eliprodil, a drug that blocks the NMDA GluN2B receptor. PET scans with the new radioligand successfully showed that the receptors are fully occupied at neuroprotective doses of eliprodil," according to the press release. "The new radioligand also provided imaging of receptor crosstalk between Sigma-1 receptors, which modulate calcium signaling, and GluN2B-containing NMDA receptors." 

According to the press release, activated NMDA receptors increase calcium (Ca2+) in the cells, but Ca2+ levels that are too high can cause cell death. Consequently, medications that block NMDA receptors are used for various neurological conditions ranging from depression and schizophrenia to ischemic stroke and dementia. 

"The significance of the work lies in the fact that we have for the first time developed a useful PET radioligand that can be applied to image the GluN2B receptor subunit of the NMDA receptor complex in humans," said co-author Simon Ametamey, PhD, of the Institute of Pharmaceutical Sciences, ETH Zurich, in Switzerland, in a prepared statement. "The availability of such a PET radioligand would not only help to better understand the role of NMDA receptors in the pathophysiology of the many brain diseases in which the NMDA receptor is implicated, but it would also help to select appropriate doses of clinically relevant GluN2B receptor candidate drugs. Administering the right dose of the drugs to patients will help minimize side-effects and lead to improvement in the efficacy of the drugs."