Zinc: moderator in brain cell chatter?

Zinc: Moderator in brain cell chatter?

Scientists have had few clues as to why there are highconcentrations of zinc in some areas of the brain, but new findings suggest a broad regulatory role for the metal that could have implications for understanding learning mechanisms and treating certain brain disorders. Zinc apparently helps control chemical communication between brain cells by modifying nerve cell receptors to different chemical messages, called neurotransmitters, say researchers at Stanford (Calif.) Medical School. The metal can either block certain receptors or enhance the activity of others, thus influencing how neurotransmitter chemicals affect a neuron, according to a report in the May 1 SCIENCE.

Using cultured mouse brain cells and microelectrodes,Dennis Choi, Steve Peters and Jae-Young Koh recorded the amount of intracellular electric current, which is used as a measurement of neurotransmitter action. They perfused the cell cultures with a variety of substances, particularly those chemicals known to affect the cells' surface receptors for the neurotransmitter glutamate. Neurons have three different types of glutamate receptor on their surface, and data from the Stanford group show that zinc helps control which type binds the neurotransmitter.

Perhaps most important is the metal's influence on the so-calledN-methyl-D-aspartate (NMDA) receptor, which is blocked when increased levels of zinc are released into the synapse, or space between nerve cells. The NMDA receptors have been proposed as docking places for chemical mediators of learning and, when overactive, for brain substances that cause seizures as well as nerve cell death like that seen in Huntington's disease. Based on their research, the authors suggest that zinc may suppress overstimulation of these receptors, thereby protecting the brain from injury.