Some of H&R readers may remember their weekends, and some not. R&D Magazine reports that researchers at the Washington University in St. Louis can now explain why:
They report, in The Journal of Neuroscience, that exposure to large amounts of alcohol does not necessarily kill brain cells as once was thought. Rather, alcohol interferes with key receptors in the brain, which in turn manufacture steroids that inhibit long-term potentiation (LTP), a process that strengthens the connections between neurons and is crucial to learning and memory. …
The brain cells affected by alcohol are found in the hippocampus and other brain structures involved in advanced cognitive functions. Izumi and first author Kazuhiro Tokuda, MD, research instructor of psychiatry, studied slices of the hippocampus from the rat brain.
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.
"It takes a lot of alcohol to block LTP and memory," says senior investigator Charles F. Zorumski, MD, the Samuel B. Guze Professor and head of the department of psychiatry. "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. It also may explain why individuals who get highly intoxicated don't remember what they did the night before."
But not all NMDA receptors are blocked by alcohol. Instead, their activity is cut roughly in half.
"The exposure to alcohol blocks some NMDA receptors and activates others, which then trigger the neuron to manufacture these steroids," Zorumski says.
The scientists point out that alcohol isn't causing blackouts by killing neurons. Instead, the steroids interfere with synaptic plasticity to impair LTP and memory formation.
"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."
Who needs those embarassing memories of excessive alcohol consumption anyway?