Why the 'Love Hormone' Oxytocin May Become a New Alzheimer's Treatment

When you hear the word oxytocin, you probably think of love. This is with good reason: Oxytocin is the primary hormone that facilitates childbirth, and all humans produce it when they fall in love. But that's not all it does, or might do. In fact, in an animal study published earlier this year, researchers found evidence that an oxytocin derivative could work as a therapy for Alzheimer's patients.

The study in question was conducted by researchers at the Tokyo University of Science in Japan, who performed a series of tests on mice. (Why mice? As with rats, mice are preferred models for research because they are so genetically and physiologically similar to humans. Also, it would be unethical to perform certain tests on humans.)

While more research is needed before these results can apply to humans, it's an important step. As the study authors point out, Alzheimer's disease is the most common form of dementia worldwide. There is currently no cure, and available treatments are only temporary.

Setting Up the Study

As we know, Alzheimer's disease is characterized by a build up of plaque deposits in the brain. Plaque deposits are abnormal clusters of protein fragments known as beta-amyloid (β-amyloid) peptides. (For clarity: A peptide is a molecule that contains between two and 50 amino acids. A protein contains 50+ amino acids.)

β-amyloid peptides collect between brain cells (called neurons), making it difficult for cells to function properly and communicate with one another. This, scientists believe, leads to progressive memory loss. As such, the Tokyo University researchers are on a mission to find ways of reversing memory loss caused by β-amyloid buildup — by testing mice.

However, finding an effective place to inject a drug into a mouse is easier said than done. For example: If the researchers fed the mice the oxytocin solution, it probably wouldn't be effective. Oxytocin is a peptide (a chain of amino acids), and peptides have a hard time crossing the blood-brain barrier. (The blood-brain barrier is a network of blood vessels that keeps harmful substances in the blood from reaching the brain.)

Previous studies have shown that oxytocin is effective when scientists inject it directly into the mouse brain. However, this technique is invasive, and would never be performed on humans. So, the Tokyo University researchers decided to administer the oxytocin derivative through the nasal passages. To find out whether a nasal delivery was just as effective as a brain delivery, they split the mice into three groups — one group received the "medicine" via the brain, one group received it via the nose, and one group had no treatment.

Testing Memory in Mice

First, the Tokyo University researchers simulated memory loss in the mice by injecting their brains with β-amyloid peptides. Then, they gave one group the "medicine" via the brain, and one group the "medicine" via the nose. Finally, the researchers had all the mice perform spatial memory tests.

One of those assessments, known as the Y maze (because the maze is shaped like a Y), tests a mouse's spatial learning and memory. In most Y mazes, the mouse gets a reward for choosing the correct arm of the maze. If the mouse has a good memory, it will start to favor the "reward" arm.

The other test is known as the Morris water maze. In this test, a mouse has to navigate an open swimming arena to find a submerged escape route. If the mouse has a good memory, it will remember where the escape route is on the next try.

The Study Results

After conducting the Y maze and Morris water maze tests on all mice, here's what the Tokyo University researchers found: The mice who received the oxytocin remedy via the brain performed well on both tests. Mice who received the remedy via the nose performed well on the Y-maze test.

While the nasal treatment didn't work as well as the brain treatment, it was important to try, because a nasal delivery is much more practical for humans. Thus, an oxytocin derivative could one day become a treatment for human Alzheimer's patients. Though more research needs to be done to understand the benefits of oxytocin and how it affects the brain, this study could become a key piece of research in the race to find a cure.