Bypassing the Blood-Brain Barrier: Further Applications from Addiction to Depression and other Psychiatric Diseases

For the first time in history, the brain’s nearly impenetrable defense against all manner of blood-borne pathogens—the esoteric blood-brain barrier—has been breached.

Scientists at the Sunnybrook Health Sciences Centre in Canada have discovered a way to non-invasively transport essential drug treatments across the brain’s natural barricade—with potential further applications for Alzheimer’s disease, Parkinson’s disease, addiction and other psychiatric diseases.

Soon, hospitals and drug rehab centers alike will be able to bypass the brain’s main line of defense in order to deliver targeted, specific drug treatments.

The blood-brain barrier is a highly selective wall that separates brain tissue and extracellular fluid from circulating blood. Composed of a line of cells called astrocytes, tight junctions are formed between the blood vessels and the neural tissue, keeping bacteria, viruses and other potential toxins out of the brain.

While the blood-brain barrier prevents potential contaminants from causing fatal damage to the central nervous system, it keeps invasive chemicals out without discrimination. This has posed a serious problem to researchers studying neural disorders at hospitals and rehab centers worldwide, as 98 percent of modern medications are unable to enter the brain this way.

The groundbreaking new method from scientists in Toronto, however, intends to change that.

The ongoing study utilized tiny microscopic air bubbles in conjunction with MRI-guided ultrasonic waves to temporarily disrupt the blood-brain barrier, allowing chemotherapy drugs directly into the site of a malignant brain tumor. The specific type of brain tumor targeted (called a glioma) is one that is especially hard to treat, due to its nature of spreading into neighboring brain tissue.

How were tiny air bubbles able to break through the otherwise-impenetrable barrier? When microscopic air bubbles are exposed to energy through sonication—the type of ultrasound used to monitor babies in the womb—they expand and compress rapidly, vibrating in a way that can temporarily poke holes in the blood-brain barrier.

In the study, researchers intravenously administered these microscopic air bubbles together with chemotherapy drugs that were otherwise incapable of passing through the barrier. The combination of microbubbles and chemo traveled through the bloodstream into the capillaries that serve the brain.

The researchers then targeted the area of the tumor with ultrasound waves so that when the drug-microbubble mixture reached the area, the vibrating bubbles temporarily broke down the barrier, allowing the chemotherapy drugs to directly enter the tumor site.

Initial brain scans suggest the treatment was successful, and the scientists are now examining the later surgically-removed tumor for concentrations of chemotherapy drug. Nine more cancer participants are scheduled to take part in the study.

While the current results are preliminary, the research stands to revolutionize the way doctors and rehab centers treat brain disorders. In their official statement, the researchers suggest the new non-invasive technology could be used in the treatment of not only brain cancer, but Alzheimer’s disease and Parkinson’s disease as well.

While chronic brain diseases are a natural choice for the new technique, the potential applications go much farther. According to Bart De Strooper, co-director of the Leuven Institute for Neuroscience and Disease in Belgium, the breaching of the blood-brain barrier could open up targeted drug treatments for clinical depression, schizophrenia and even addiction.

Addiction rehab centers have long used prescription drugs in the treatment of substance abuse and alcohol addictions. From selective serotonin re-uptake inhibitors and monoamine oxidase inhibitors used to treat co-occurring depression to opioid antagonist naltrexone to control cravings in both heroin addicts and alcoholics, all these drugs are more are employed by rehab centers.

These drugs and others similar aim to disrupt the reward pathway in the brain, a neural circuit that projects from the ventral tegmental area to the nucleus accumbens and the prefrontal cortex. This pathway is heavily involved in addictive behaviors, and as such represents a natural target for the kinds of drug therapy techniques employed by rehab centers.

However, the problem with such drugs is that while they are able to pass the blood-brain barrier, they do so indiscriminately. In other words, when these drugs are administered, they affect neurotransmitters all over the brain, not just in the cells of the reward pathway. This has caused some of the main issues plaguing these kinds of treatments, such as the tendency of strong antidepressants to induce psychosis in some patients.

Until now, there was no way for rehab centers to administer targeted drug treatment to a specific area of the brain. With the use of microbubble transmission, however, new drugs can be manufactured to pass through the blood-brain barrier only in response to ultrasound radiation—and only at the site singled out for treatment.

In addition to treating the addiction itself, the new microbubble treatment can also be employed in the treatment of a plethora of disorders commonly associated with drug and alcohol addiction, such as anxiety, bi-polar attention and depressive disorders.

This new literal breakthrough stands to forever change the way doctors at hospitals and rehab centers treat neural disorders. From cancer to dementia and depression, specialized drug treatments will be able to enter the brain non-invasively, temporarily, and ultimately safely.

Addiction and its co-occurring mental disorders affect millions of people around the world every year. While addiction is comprised of both physiological and behavioral components, addiction is fundamentally a medical condition, not a moral failing.

Through further research on the applications of ultrasound and microbubble drug transport, hospitals and rehab centers across the globe will be able to better target specific brain areas for treatment, for better patient neural health and overall wellbeing.


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