Featured Research

from universities, journals, and other organizations

The biology behind alcohol-induced blackouts

Date:
July 10, 2011
Source:
Washington University School of Medicine
Summary:
Neuroscientists have identified the brain cells involved in alcohol-related blackouts and the molecular mechanism that appears to underlie them. Alcohol interferes with key receptors in the brain, which in turn manufacture steroids that inhibit long-term potentiation, a process that strengthens the connections between neurons and is crucial to learning and memory.

When exposed to large amounts of alcohol, neurons in the hippocampus produce steroids (shown in bright green, at left), which inhibit the formation of memory. Pictured at right, neurons in the same region of the brain that have not been exposed to alcohol.
Credit: Kazuhiro Tokuda

A person who drinks too much alcohol may be able to perform complicated tasks, such as dancing, carrying on a conversation or even driving a car, but later have no memory of those escapades. These periods of amnesia, commonly known as "blackouts," can last from a few minutes to several hours.

Now, at Washington University School of Medicine in St. Louis, neuroscientists have identified the brain cells involved in blackouts and the molecular mechanism that appears to underlie them. They report July 6, 2011, 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.

Better understanding of what occurs when memory formation is inhibited by alcohol exposure could lead to strategies to improve memory.

"The mechanism involves NMDA receptors that transmit glutamate, which carries signals between neurons," says Yukitoshi Izumi, MD, PhD, research professor of psychiatry at Washington University School of Medicine in St. Louis. "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."

Izumi says the various receptors involved in the cascade interfere with synaptic plasticity in the brain's hippocampus, which is known to be important in cognitive function. Just as plastic bends and can be molded into different shapes, synaptic plasticity is a term scientists use to describe the changeable properties of synapses, the sites where nerve cells connect and communicate. LTP is the synaptic mechanism that underlies memory formation.

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."

Stress on the hippocampal cells also can block memory formation. So can consumption of other drugs. When combined, alcohol and certain other drugs are much more likely to cause blackouts than either substance alone.

The researchers found that if they could block the manufacture of steroids by neurons, they also could preserve LTP in the rat hippocampus. And they did that with drugs called 5-alpha-reductase inhibitors. These include finasteride and dutasteride, which are commonly prescribed to reduce a man's enlarged prostate gland. In the brain, however, those substances seem to preserve memory.

"We would expect there may be some differences in the effects of alcohol on patients taking these drugs," Izumi says. "Perhaps men taking the drugs would be less likely to experience intoxication blackouts."

The researchers plan to study 5-alpha-reductase inhibitors to see how easily they get into the brain and to determine whether those drugs, or similar substances, might someday play a role in preserving memory.

This work was supported by grants from the National Institute of Mental Health, the National Institute of General Medical Sciences, and the National Institute on Alcohol Abuse and Alcoholism of the National Institutes of Health (NIH), and by the Bantley Foundation.


Story Source:

The above story is based on materials provided by Washington University School of Medicine. The original article was written by Jim Dryden. Note: Materials may be edited for content and length.


Journal Reference:

  1. Tokuda K, Izumi Y, Zorumski CF. Ethanol enhances neurosteroidogenesis in hippocampal pyramidal neurons by paradoxical NMDA receptor activation. The Journal of Neuroscience, Vol. 31(27), pp. 9905-9909. July 6, 2011

Cite This Page:

Washington University School of Medicine. "The biology behind alcohol-induced blackouts." ScienceDaily. ScienceDaily, 10 July 2011. <www.sciencedaily.com/releases/2011/07/110707092439.htm>.
Washington University School of Medicine. (2011, July 10). The biology behind alcohol-induced blackouts. ScienceDaily. Retrieved October 2, 2014 from www.sciencedaily.com/releases/2011/07/110707092439.htm
Washington University School of Medicine. "The biology behind alcohol-induced blackouts." ScienceDaily. www.sciencedaily.com/releases/2011/07/110707092439.htm (accessed October 2, 2014).

Share This



More Mind & Brain News

Thursday, October 2, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Pregnancy Spacing Could Have Big Impact On Autism Risks

Pregnancy Spacing Could Have Big Impact On Autism Risks

Newsy (Oct. 1, 2014) A new study says children born less than one year and more than five years after a sibling can have an increased risk for autism. Video provided by Newsy
Powered by NewsLook.com
Stopping School Violence

Stopping School Violence

Ivanhoe (Oct. 1, 2014) A trauma doctor steps out of the hospital and into the classroom to teach kids how to calmly solve conflicts, avoiding a trip to the ER. Video provided by Ivanhoe
Powered by NewsLook.com
Pineal Cysts: Debilitating Pain

Pineal Cysts: Debilitating Pain

Ivanhoe (Oct. 1, 2014) A tiny cyst in the brain that can cause debilitating symptoms like chronic headaches and insomnia, and the doctor who performs the delicate surgery to remove them. Video provided by Ivanhoe
Powered by NewsLook.com
Burning Away Brain Tumors

Burning Away Brain Tumors

Ivanhoe (Oct. 1, 2014) Doctors are 'cooking' brain tumors. Hear how this new laser-heat procedure cuts down on recovery time. Video provided by Ivanhoe
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Health & Medicine

Mind & Brain

Living & Well

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins