Communication in the brain travels from one nerve cell to another through critical connections called synapses. These neuron-to-neuron junctions form early in brain development, and their construction was thought to be guided by the nerve cells themselves.
Now, investigators supported by the National Institute on Drug Abuse (NIDA), National Institutes of Health, have discovered that cells called glia, known to provide support for neurons in the mature brain, also play a crucial role in formation of synapses during the surge of development following birth. This key insight into the process of normal synapse development may lead to improved treatment of conditions such as drug addiction and epilepsy, which are characterized in part by too many synapses. The research, led by Dr. Ben Barres of Stanford University School of Medicine in Stanford, California, is reported in the February 11, 2005 issue of the journal Cell.
"Synapses are the key connections between cells in the brain. We know that drugs alter these connections, and that the developing brain is vulnerable to addictive drugs' disruption of normal communication," says NIDA Director Dr. Nora D. Volkow. "Compounds that direct synapse formation may offer a therapeutic option for people fighting drug addiction or other neurologic conditions."
Glia account for 90 percent of the cells in a mammalian brain, but until recently scientists focused mainly on the supportive role that glial cells play in helping mature neurons survive. Dr. Barres, along with Stanford postdoctoral fellows Dr. Karen Christopherson and Dr. Erik Ullian, developed a method for growing neurons in a laboratory without glial cells. Then they isolated proteins produced by glial cells and observed the effect when they added the proteins to a culture of neurons. Two of the proteins, thrombospondin 1 and 2, led to the development of synapses -- albeit functionally incomplete ones.