If you're extremely drunk, there's no point in reading this article now.

Come tomorrow, you won't remember these words or anything that follows. The brain refuses to store memories when its under the influence of large amounts of alcohol.

If, however, you're a really inebriated bald guy who uses Propecia, read on. Your memory might serve you well.

Scientists in the psychiatry department at Washington University have begun unraveling the mystery of why blackouts happen. And much to their surprise, the bouts of amnesia don't appear to kill brain cells.

Instead, high concentrations of alcohol interfere with a process in the brain's hippocampus — the part that strengthens connections between neurons and is vital for memory and learning — called long-term potentiation. Dr. Yukitoshi Izumi, research professor of psychiatry at Washington U., said researchers have known that for a while. But when they studied slices of brain from rats recently, they were able to uncover the mechanisms that stop long-term potentiation.

Izumi and his fellow researchers assumed that high concentrations of alcohol would interfere with long-term potentiation by completely shutting down the neurons' glutamate receptors, structures on the surface of cells that receive chemical signals from nearby cells.

Instead, the alcohol blocked about half of a certain type of glutamate receptor and left the other half unblocked. And the unblocked ones received glutamate in a highly erratic fashion.

Glutamate molecules act as stimuli messengers by carrying signals between neurons. Too much or too little activation of the receptors can be toxic, and irregular doses of glutamate prompt neurons to over-produce a steroid that inhibits long-term potentiation.

Propecia findings

According to Dr. Charles Zorumski, head of psychiatry and professor of neurobiology at Washington U., they have discovered something equally exciting: that Propecia, a drug used to treat enlarged prostates and male-pattern baldness by blocking production of a male hormone, stops alcohol-soaked neurons from producing the steroids.

In short, Zorumski said, Propecia can stop alcohol's effects on long-term potentiation, and possibly even blackouts. He and his colleagues intend to study the drug further.

This study focuses on the inability to retain memory, Zorumski said. Other parts of the brain are responsible for slurred speech, falling down, passing out and poor judgment. But they think the cellular mechanisms at work here might be the same or similar across other regions of the brain.

Learning about the mechanisms that underlie memory formation could lead to treatments for traumatic brain injuries, strokes, Alzheimer's disease and other conditions that affect memory, Izumi said. "And alcohol is a problem that's so common in our country."

He noted that he had to administer high concentrations of ethanol to the rat's brain tissue in a short period of time to inhibit LTP. And he estimates that a person would have to reach a blood-alcohol level between 0.3 and 0.4 percent relatively quickly for a blackout to happen. That's three to four times the legal driving limit of .08 percent.

Other studies have found that drinking while under severe emotional stress or the influence of certain narcotics appears to disrupt long-term potentiation and cause blackouts, even with lower alcohol blood levels.

Getting slightly buzzed or reaching a high-level of intoxication gradually over several hours doesn't seem to cause the periods of amnesia, however.

Izumi and Zorumski stress that repeated bouts of severe intoxication will cause problems, including cell loss that can lead to dementia. And repeated hangovers, which is the body's way of withdrawing from alcohol, are bad for the brain.

But any individual blackout doesn't appear to kill neurons or do irreparable harm in the hippocampus, Izumi said.

Zorumski believes that blacking out is a protective mechanism.

"They lead some people to think, 'Well maybe I shouldn't keep drinking,' " he said.