Spraying drugs up the nose may help heal the brain after a stroke

Antibody molecules sprayed into the noses of rats led to the repair of stroke-like damage to the brain.

To Claire Wilson

Medicines that combat the effects of stroke can be delivered to the brain, at least in rats, by squirting them through their noses.

Getting large drug molecules into the brain has long been viewed as a significant medical challenge. Most such compounds cannot reach the brain in large amounts because the walls of the blood vessels that perfuse the brain are highly impermeable, creating what is known as the blood-brain barrier.

Previous research has suggested that some drugs may be able to reach the brain through the nose because the nerve cells that sense smell have long fibers that extend from the nasal cavity to the brain.

But it’s unclear whether the molecules will travel to the brain in sufficient quantities to provide medical benefit, says Martin Schwab of the Swiss Federal Institute of Technology in Zurich.

To find out, Schwab and his colleagues tested nasal delivery of an antibody that blocks a compound in the brain called Nogo-A that normally inhibits brain cell growth.

The team first mimicked the effects of a stroke in rats by shutting off blood flow to parts of the brain. This means that the animals have become clumsy reaching through the pellet holes. This could have easily been done in advance.

In rats that received a nasal spray of antibodies once daily for 2 weeks, the success rate for this task improved to approximately 60% of their previous ability 4 weeks after injury. This figure was approximately 30% in placebo-treated animals.

When Schwab’s team examined rat brains, they found that treated rats sprouted more new nerve fibers. “We have reached levels of antibodies that are effective in repairing large lesions in stroke,” Schwab said. “This shows that there is a natural regenerative power within the brain, and we need to let go of the brakes to make it happen.”

Moein Moghimi of the University of Newcastle, UK, says any method of getting drugs into the brain would have wide-ranging benefits. However, this study does not prove that the antibody traveled up the nerve to the brain. This is because the antibodies may have been absorbed through the nose into the bloodstream, from where small amounts may have reached the brain.

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