( To the multitude of substances that reg...)Zinc plays important role in brain circuitry

To the multitude of substances that regulate neuronal signaling in the brain and spinal cord add a new key player: zinc. By engineering a mouse with a mutation affecting a neuronal zinc target, researchers have demonstrated a central role for zinc in modulating signaling among the neurons. Significantly, they found the mutant mouse shows the same exaggerated response to noise as children with the genetic disorder called "startle disease," or hyperekplexia.

The findings shed light on a nagging mystery in neurobiology: why the connections among certain types of neurons contain considerable pools of free zinc ions. And even though many studies had shown that zinc can act toxically on transmission of neural impulses, half a century of experiment researchers had not been able to show conclusively that the metal plays a role in normal nerve cell transmission.

However, in an article in the November 22, 2006, issue of the journal Neuron, published by Cell Press, Heinrich Betz and colleagues conclusively demonstrate just such a role for zinc.

In their experiments, the researchers produced mice harboring a mutant form of a gene for a receptor for zinc in neurons--thereby compromising the neurons' ability to respond to zinc. The mutation in the receptor, called the glycine receptor, targets the same receptor known to be mutated in humans with hyperekplexia. The receptor functions as a modulator of neurons in both motor and sensory signaling pathways in the brain and spinal cord.

The genetic approach used by the researchers was a more targeted technique than previous experiments in which researchers reduced overall neuronal zinc levels using chemicals called chelators that soak up zinc ions.

The resulting mutant mice showed tremors, delayed ability to right themselves when turned over, abnormal gait, altered transmission of visual signals, and an enhanced startle response to sudden noise.

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Source:Cell Press

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