A new study found that chronic alcohol consumption reduces the number of new brain cells that form in the hippocampus of adolescent rhesus monkeys. This finding suggests that these cells are vulnerable to alcohol and their presence may be essential for preventing alcohol dependence. Science Daily reports that the findings were presented at Neuroscience 2009, the annual meeting of the Society for Neuroscience and the world's largest source of emerging news about brain science and health. "We've found a potential mechanism for alcohol's harmful effects on the hippocampus and other brain regions associated with executive function and memory," said Chitra Mandyam, PhD, of the Scripps Research Institute in San Diego and lead author of the study. "This may lead to more effective medications for helping alcoholics overcome their addiction." In this study, male rhesus monkeys (aged four to five years early in the study and five to six years at the end) were allowed to voluntarily consume a Tang-sweetened solution containing 6 percent alcohol during one-hour sessions, Monday through Friday. A control group of monkeys had similar access to alcohol-free Tang. The alcohol group consumed an average of 1.78 g\/kg of alcohol per session. After five months the primates' brain tissue was analyzed, with careful attention to sections containing the hippocampus for signs of neurogenesis, or creating of new brain cells. The researchers found that chronic alcohol consumption significantly altered neurogenesis in the region of the hippocampus that produces self-renewing neural stem cells. Specifically, the alcohol-consuming monkeys exhibited a 58 percent decrease in proliferation (stem cell birth) and a 63 percent decrease in differentiation and neurogenesis (stem cell survival). "Our results demonstrate that in addition to causing existing cells to degenerate, excessive alcohol keeps new stem cells from forming," Mandyam said. Research was supported by the National Institutes of Health.