Synaptic vesicles help relay messages.

• Position: Brain Function - University of Texas southwestern medical center, Dallas

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 neutrons.

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 the same synaptic vesicles were responsible for releasing neurotransmitters in both modes. However, research by scientists at the University of Texas Southwestern Medical Center, Dallas, suggests that two distinct types of synaptic vesicles are responsible for the different modes of neurotransmitter release.

"These findings question one of the core tenets of synaptic function and reveal significant complexity in organization of synaptic vesicles within individual synapses," reports Ege Kavalali, assistant professor in the Center for Basic Neuroscience and of physiology.

Neurotransmitters regulate many different aspects of mood, cognition, and behavior, such as emotional state...