Imagine a blood test that could diagnose depression and also indicate whether a particular antidepressant therapy is working. That could be the eventual outcome of a recent study by Mark M. Rasenick of the University of Illinois, Chicago, and colleagues (J. Neurosci. 2008, 28, 3042). The researchers studied the location of a protein called Gsα in postmortem samples of human brain cells. In depressed people, the team discovered, the protein accumulates within localized, cholesterol-rich "lipid raft" sections of cell membranes. This sequestration dampens the intracellular action of certain neurotransmitters and appears to be associated with depression, Rasenick says. His team and others have previously shown in rats and cultured brain cells that antidepressants move Gsα from lipid rafts to other areas in the membrane where the protein can more effectively pave the way for neurotransmitter action. Some evidence indicates Gsα behaves the same in cells outside the brain, Rasenick notes. If that behavior is confirmed, a simple blood test could diagnose and evaluate the treatment of depression.