Every time we move, feel emotions, think or remember, the nerve cells, or neurons, in our body transmit messages to one another via chemical signals called neurotransmitters. Within neurons are tiny organelles called synaptic vesicles that sequester neurotransmitters and release them when needed into the synapse, or space between nerve cells, where the chemical signal is transmitted to other neurons.

It is known that synaptic vesicles release their neurotransmitters in two different "modes" one when the neuron is stimulated and actively relaying a message, and the other through spontaneous release when the neuron is "at rest," or inactive. Until now it was believed that the same synaptic vesicles were responsible for releasing neurotransmitters in both modes.

However, new research by UT Southwestern scientists appearing in the Feb. 17 issue of the journal Neuron suggests that two distinct types of synaptic vesicles are responsible for the two different modes of neurotransmitter release one type of vesicle for spontaneous release, another vesicle associated with activity-dependent release.

"These findings question one of the core tenets of synaptic function and reveal significant complexity in organization of synaptic vesicles within individual synapses," said Dr. Ege Kavalali, assistant professor in the Center for Basic Neuroscience and of physiology at UT Southwestern and senior author on the study.

Neurotransmitters regulate many different aspects of mood, cognition and behavior, such as emotional state, reactions to stress, pain, and the physical drives of sleep, appetite and sexuality.

A better understanding of such fundamental mechanisms of neurotransmitter release will aid researchers in their investigations of psychiatric disorders and neurologic
'"/>

Contact: Amanda Siegfried
amanda.siegfried@utsouthwestern.edu
214-648-3404
UT Southwestern Medical Center
16-Feb-2005