The researchers believe their discovery provides a "molecular mechanism" that may help to explain some of the pathology of a certain form of epilepsy, Alzheimer's and Parkinson's diseases, nicotine addiction, and depression.

Neurotransmitter receptors are specialized molecules located on the outside of cells. A neurotransmitter binds to the receptor and, in effect, carries information into the cell. The natural neurotransmitter that ordinarily binds to this nicotinic receptor and carries messages throughout the nervous system and the brain is acetylcholine, a chemical released from one nerve cell to elicit an electrical signal in the next cell within the circuit.

Although acetylcholine is the usual "activator" of this receptor, it is also so-named as it binds and responds to nicotine. The scientists said that this nicotinic receptor, to which nicotine binds, exists in a subset of nerve cells in the hippocampus. This receptor was studied through a technique which records electrical nerve impulses in individual nerve cells. The researchers -- Susan Jones, Ph.D., and Jerrel L. Yakel, Ph.D., worked with thin slices of rat hippocampus which is similar to, but much smaller than, a human's. The scientists reported their work in the Journal of Physiology, Volume 504, #3. Both are with the Laboratory of Signal Transduction at NIEHS, an Institute of NIH, located in Research Triangle Park, N.C.

Dr. Yakel said the identification of this receptor in the hippocampus may have relevance to nicotine's apparent enhancement of memory in some Alzheimer's patients, nicotine addiction, and a rare form of epilepsy.

The receptor's function may be a key to understanding epilepsy and Alzheimer's disease, Dr. Jones added, but it may also be important in other diseases such as Parkinson's or depression. "Basic research like this can ultimately lead to disease-specific solutions," Dr. Jones said.