Receptor involved in brain injury found.

Two independent research groups -- one in Japan, the other in Kansas -- have reported isolating two different forms of a specific nerve-cell receptor that may play a role in brain damage caused by stroke, epilepsy or head injury.

Both teams claim they have found in rats the receptor for glutamate, a neutransmitter involved in nervous system development and memory storage. Brain cell s appear to release glutamate in increased amounts after injury, and neurologists believe the so-called NMDA receptor (named for its ability to bind to the lab-made chemical N-methyl-D-aspartate) can kill nerve cells when overstimulated by glutamate.

Elias Michaelis of the University of Kansas in Lawrence says the NMDA receptor purified by his group can bind to both glutamate and NMDA. He and his colleagues found that they could block the binding of both chemicals by first adding antibodies that stick to the receptor. Further, they found that adding fibroblast growth factor -- which also promotes nerve-cell growth --reduced the number ofNMDA receptors on lab-cultured nerve cells, protecting them from death by overexcitation.

Michaelis and his colleagues published some of their results in the Nov. 7 NATURE. In the same issue, Shigetada Nakanishi and co-workers at Kyoto University reported purifying a candidate NMDA receptor with a very different structure.

Michaelis contends that both groups have uncovered NMDA receptors, but of different types. Neuroscientist Charles F. Stevens remains skeptical. Stevens, of the Salk Institute for Biological Studies in La Jolla, Calif., says he believes Nakanishi's team has found all or part of the real NMDA receptor, but he questions the Kansas researchers' finding because their candidate receptor bears no structural similarity to previously described receptors for other molecules.