Why we pass out after drinking too much

Until now, scientists had no clue why people after drinking too much alcohol and performing complicated tasks, such as dancing, carrying on a conversation or even driving a car, later forget these escapades.

These periods of amnesia, commonly known as 'blackouts', can last from a few minutes to several hours.

Representational pic

Now, neuroscientists at the Washington University School of Medicine in St. Louis have identified the brain cells involved in blackouts and the apparent underlying molecular mechanism.

They reported 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 mechanism involves NMDA receptors that transmit glutamate, which carries signals between neurons,' said Yukitoshi Izumi, 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,' added Izumi.

'It takes a lot of alcohol to block LTP and memory,' said senior investigator Charles F. Zorumski, 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,' added Zorumski.

'The exposure to alcohol blocks some NMDA receptors and activates others, which then trigger the neuron to manufacture these steroids,' said Zorumski.

The study is detailed in The Journal of Neuroscience.