Laser Light Reveals How Cocaine Cuts Blood Flow to Brain
Use of the stimulant drug cocaine is linked to increased risks for experiencing a potentially fatal change in blood vessel health known as a stroke. However, researchers have not previously known how this drug produces its damaging effects inside the brain’s blood vessels. In a study published in September 2014 in the journal Biomedical Optics Express, researchers from two U.S. institutions used laboratory testing on mice to explore the underlying mechanisms of cocaine-related blood vessel damage inside the brain. These researchers concluded that the drug produces its harmful impact by severely reducing blood flow in affected blood vessels.
Strokes are the product of a lack of fresh supplies of oxygen-bearing blood inside the brain. The brain relies on a continual flow of oxygen to keep its tissues healthy and perform its vast range of everyday tasks. When this flow is cut off or seriously diminished, the tissues associated with the affected blood vessels can irreversibly die off in a matter of minutes. Potential results of such a die-off include permanent loss of function in the part(s) of the body controlled by the damaged brain area and death.
The most common form of stroke, ischemic stroke, occurs when something blocks the blood flow inside at least one of the arteries that funnel oxygen-bearing blood to the brain. Typical causes of artery blockage include cholesterol-based plaque deposits and blood clots; both plaque deposits and blood clots can form locally in or near the brain, or travel through the bloodstream from other parts of the body. A second form of stroke, hemorrhagic stroke, occurs when an artery inside the brain starts leaking blood into the surrounding tissue or bursts open. The pressure buildup associated with the pooling of blood inside the skull can severely damage nearby nerve cells. Along with heart attacks, the two forms of stroke are prominent sources of fatalities in much of the industrialized world, including the U.S.
Cocaine Use and Stroke Risks
Use of cocaine dramatically increases the short-term risks for an ischemic stroke, according to findings reported to the American Stroke Association in 2014 by researchers from the University of Maryland and the Department of Veterans Affairs. In fact, for a full day following use of the drug, the odds of experiencing this type of stroke increase roughly 500 percent to 600 percent. Repeated cocaine use is also linked to atherosclerosis (hardening of the arteries), a condition known to increase the risks for an ischemic stroke. In addition, some studies indicate that cocaine use increases the odds for the onset of a hemorrhagic stroke.
Cocaine and Blood Vessels
In the study published in Biomedical Optics Express, researchers from Stony Brook University and the National Institute on Drug Abuse used a new, laser-based technique called ODT (optical coherence Doppler tomography) to assess the impact that cocaine use has on the amount of blood flowing through the brain’s blood vessels. ODT scans measure blood flow by analyzing the amount of laser light that bounces off a blood vessel’s outer wall. A vessel with normal blood flow reflects a lot of light back, while a vessel with reduced flow reflects a smaller amount of light. The researchers used an advanced form of ODT that offsets some of the known drawbacks of this imaging technique. Rather than conduct experiments on humans (an ethically questionable approach), they used mice as stand-ins.
Some of the mice involved in the study received regular doses of cocaine over the course of a month. Other mice received several doses of the drug over much shorter spans of time. After reviewing the results of the ODT imaging, the researchers concluded that both methods of cocaine use produced a serious drop in blood flow in the brain’s main arteries. In some cases, the observed blood flow drops were severe enough to essentially cut off the supply of oxygen-bearing blood reaching the brain. In turn, lack of this blood created the conditions for the onset of an ischemic stroke.
The study’s authors believe that improved understanding of the way in which cocaine interferes with brain blood flow could lead to improved treatments for cocaine users at risk for an ischemic stroke. They also believe that the ODT imaging techniques they developed have additional usefulness for doctors performing brain surgery, as well as for the future bioengineering of replacement blood vessels.