Spraying drugs into the nose can help heal the brain after a stroke

Antibody molecules sprayed into the noses of rats led to the repair of stroke-like brain damage, and this may be due to the fact that drugs passed through the nerve cells for smell.

Drugs that fight the effects of a stroke can be delivered to the brain by injecting them through the nose — at least in rats.

Getting large drug molecules into the brain has long been considered a key medical problem. Most of these compounds cannot enter the brain in large quantities because the walls of the blood vessels that supply the brain with blood are very impermeable, creating the so-called blood-brain barrier.

Previous research has suggested that some drugs may enter the brain through the nose, traveling along the nerve cells that detect odor because they have long fibers that extend from the nasal passages to the brain.

However, it was unclear whether enough molecules would reach the brain to be of medical benefit, says Martin Schwab of the Swiss Federal Institute of Technology in Zurich.

To find out, Schwab and colleagues tested nasal delivery of antibodies that block a brain compound called Nogo-A, which normally inhibits brain cell growth.

The team first mimicked the effects of a stroke in rats by cutting off blood flow to parts of their brains. This meant that the animals became more clumsy in getting food pellets through the hole, which they could easily do beforehand.

In rats treated with an antibody nasal spray once a day for two weeks, their performance on this task improved to about 60 percent of their previous ability four weeks after injury. In animals treated with placebo, this figure was about 30 percent.

When Schwab’s team examined the brains of rats, they found that the treated rats grew more new nerve fibers. “We have reached an antibody level that is effective in repairing a large stroke,” says Schwab. “It shows that there is a natural regenerative power in the brain and you just have to release the brakes for that to happen.”

Moein Mogimi of the University of Newcastle, UK, says that any way to inject drugs into the brain will have great benefits. But this study doesn’t prove that the antibodies reached the brain along the nerves, because they could have traveled from the nose into the bloodstream, where small amounts could have entered the brain, he says.

Sign up for our free Health Check newsletter for health, diet and fitness news you can trust every Saturday.