Neurons Use Chemical 'Chords' To Shape Signaling

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Neurons Use Chemical 'Chords' To Shape Signaling

http://www.sciencedaily.com/releases/2008/02/080227121905.htm

Researchers have discovered that neurons can use two different

neurotransmitters that target the same receptor on a receiving neuron

to shape the transmission of a nerve impulse. Although the

researchers' experiments identified the " co-release " of the two

neurotransmitters only in specific types of neurons in the brain's

auditory center, their finding may apply more broadly in the brain,

they said. Thus, the finding may represent a new way in which the

brain precisely modulates the nerve impulses that travel from neuron

to neuron in its circuitry.

To propagate a nerve impulse within neural circuitry, one neuron

launches a burst of chemical signal called a neurotransmitter at a

receiving neuron, where the neurotransmitter attaches to a specific

receptor--like a key fitting a lock. That neurotransmitter-specific

receptor is activated to trigger a nerve impulse in the receiving

neuron.

Such nerve impulses, however, rather than being the electrical

equivalent of a shotgun blast, are precisely modulated signals, like

the finely shaped notes of an orchestra.

Tao Lu and colleagues Rubio and ce Trussell reported

their findings in the February 28, 2008, issue of the journal Neuron.

In studies over the past several decades, researchers had found

evidence for co-release of different neurotransmitters by the same

neuron. But they had assumed that in such cotransmission, each

neurotransmitter targeted its own receptor on the receiving neuron.

However, Lu and colleagues performed biochemical and

electrophysiological experiments on rat neurons and established that

two neurotransmitters--called GABA and glycine--both target the

glycine receptor in specific types of neurons. The neurons they

studied reside in the part of the rat auditory system that processes

sound location. Thus, shaping the timing of the nerve impulse is

important for such processing.

Glycine acts as an inhibitory neurotransmitter in such neurons, and

Lu and colleagues found that GABA acts on the glycine receptor to

accelerate glycine-produced inhibition.

Lu and colleagues wrote that, although their studies only establish

the role of GABA/glycine cotransmission in the specialized auditory

neurons, other studies had found evidence for cotransmission in other

areas of the brain. Such findings hint that the two neurotransmitters

may work in concert elsewhere " at a single receptor to enhance the

temporal resolution of inhibition. "

" Of course, a hallmark of a great scientific study is the ability to

approach an established problem from a fresh perspective, " wrote

Singer in a preview of the article in the same issue of

Neuron. " And certainly the present work by Lu, Rubio, and Trussell

characterizes this. " Singer, who is at Northwestern University,

asked, " Who would have thought that GABA [is a natural trigger for

glycine receptors] " Not me, unfortunately. "

The researchers include Tao Lu, Oregon Hearing Research Center and

Vollum Institute, Oregon Health & Science University, Portland, OR;

E. Rubio, Department of Physiology and Neurobiology, University

of Connecticut, Storrs, CT; and ce O. Trussell, Oregon Hearing

Research Center and Vollum Institute, Oregon Health & Science

University, Portland, OR.