This is a special message for all you folks out there who occasionally drink to excess. A team of researchers at Washington University Medical School has figured out what happened to you last time you blacked out!
OK, they can't explain how you ended up in a bar on the completely opposite end of town as the one you remember walking into or confirm whether you really did perform that horribly embarrassing karaoke routine that everyone keeps hinting at. Come on, they're scientists, not psychics. But they can confirm something you may be obsessing about: No, you did not kill any of your brain cells.
You can rest easy now. But read on for some exciting biological fun facts from the cutting edge of neuroscience, culled from an article that appeared yesterday in the Journal of Neuroscience.
Here's what really happened: All that alcohol you consumed messed with some receptors in your brain called NMDA receptors which, in turn, told your neurons to start producing steroids that inhibited long-term potentiation, or LTP, a process that builds connections between neurons. In other words, too much drinking (and drug-taking, too, for that matter) interferes with our ability to make memories.
"It takes a lot of alcohol to block LTP and memory," says senior investigator Dr. Charles F. Zorumski, in a press release. "But 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. The exposure to alcohol blocks some NMDA receptors and activates others, which then trigger the neuron to manufacture these steroids."
Two researchers, Dr. Yukitoshi Izumi and Dr. Kazuhiro Tokuda, found all this out by extracting rat brains and taking slices of the section called the hippocampus, which controls the memory (and, incidentally, spacial navigation, which could explain a bunch of other things). They doused the hippocampus cells with alcohol. Moderate amounts didn't have any effect on LTP, but excessive quantities did.
Surprisingly, there was no physical damage to the cells.
"Alcohol isn't damaging the cells in any way that we can detect," Zorumski says. "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."
Now the researchers are experimenting with ways to keep the neurons from producing the memory-inhibiting steroids when the NMDA receptors go haywire. Mostly, they've been injecting the rat brain cells with 5-alpha-reductase inhibitors, a class of drug that includes finasteride and dutasteride, both used to reduce the swelling of men's prostate glands.
It seems to be working, in the rat brains at least. Next they're going to see how easily the drugs can get to the human brain. But it looks like it'll be a long time before they start passing memory-preservation drugs out in bars.