Brain Cells Are Not Killed During Alcohol-Induced Blackouts Say Researchers

Posted on August 14, 2011

Sometimes people drinking large amounts of alcohol will experience a blackout, a short period of amnesia that can last from a few minutes to several hours. People may dance, talk or even drive a car (bad idea) during these blackouts. These intoxicated people will have no recollection of the time period the next day and will likely have to find out from other people what exactly they did during their blackout.

It has been thought that brain cells are killed during alcohol-induced blackouts, but new research suggests that is not the case. Researchers say large amounts of alcohol interferes with memory formation in the brain, but does not kill brain cells.

Neuroscientists at the Washington University School of Medicine in St. Louis say alcohol interferes with key receptors in the brain which manufacture steroids that inhibit long-term potentiation (LTP), a process that strengthens the connections between neurons and is crucial to memory.

Senior investigator Charles F. Zorumski, MD, the Samuel B. Guze Professor and head of the Department of Psychiatry, says, "Alcohol isn't damaging the cells in any way that we can detect. As a matter of fact, even at the high levels we used here, we don't see any changes in how the brain cells communicate. You still process information. You're not anesthetized. You haven't passed out. But you're not forming new memories."

Yukitoshi Izumi, MD, PhD, research professor of psychiatry at Washington University School of Medicine, says, "The mechanism involves NMDA receptors that transmit glutamate, which carries signals between neurons. An NMDA receptor is like a double-edged sword because too much activity and too little can be toxic. We've found that exposure to alcohol inhibits some receptors and later activates others, causing neurons to manufacture steroids that inhibit LTP and memory formation."

The researchers, who studied the impact of alcohol on slices of the hippocampus from rat brains, say it takes a lot of alcohol to inhibit memory formation. When they treated hippocampal cells with moderate amounts of alcohol, LTP was unaffected, but exposing the cells to large amounts of alcohol inhibited the memory formation mechanism.

Zorumski says, "It takes a lot of alcohol to block LTP and memory,b ut the mechanism isn't straightforward. The alcohol triggers these receptors to behave in seemingly contradictory ways, and that's what actually blocks the neural signals that create memories. It also may explain why individuals who get highly intoxicated don't remember what they did the night before."

The researchers also say that stress on the hippocampus cells can block memory formation as can consumption of other drugs. They also say that when combined, alcohol and certain other drugs are much more likely to cause blackouts than either substance alone.

The research was reported July 6, 2011, in The Journal of Neuroscience,