After general anesthesia, a common problem that shows up in older adults is cognitive deficits, particularly memory loss, but it’s not clear why or how they happen. In a study published in PLOS Biology, researchers have taken a step toward understanding how anesthetic drugs affect the hippocampus, a brain region involved in memory formation and storage. They tested three anesthesia treatments in mice and determined that isoflurane, an inhaled anesthetic commonly used by itself in animal studies and sometimes in combination with other drugs in people, was the least disruptive to hippocampal neurons and didn’t affect memory formation and consolidation.

The authors “not only looked at the onset of the effects and the changes during the acute phase of anesthesia, but like many studies have not done in the past, they’ve also looked at what happens after the drugs wash out,” says Beverley Orser, an anesthesiologist and neuroscientist at the University of Toronto who did not participate in the study. “The results challenge a very fundamental notion that I think the public—and many investigators even—assume. And that is, once the drugs have been eliminated from the body, the brain goes back to baseline state. And that’s not the case.”

“The most potent effects of general anesthetics relate to memory systems but these amnesic effects have been relatively understudied to this level of detail in the hippocampus,” writes George Mashour, an anesthesiologist and neuroscientist at the University of Michigan who was not involved in the study, in an email to The Scientist. In terms of next steps, “two of the three anesthetic combinations tested in this study are used primarily in animal experiments,” he adds. “Additional investigation using experimental models that include other anesthetic regimens commonly used in humans and that also include a surgical intervention will help translate these findings to clinical care.”

Read the full article at The Scientist.