NEW YORK – Melatonin, the hormone more commonly associated with jet lag and sleep cycles, may help protect the brain after a stroke, according to a new animal study.
Rats who received a dose of melatonin within two hours of a stroke experienced less tissue damage than rats who either received melatonin later or not at all.
Reducing tissue damage after a stroke can cut the overall amount of brain damage and help with recovery, study author Dr. Raymond Tak Fai Cheung said.
If these results apply to humans, melatonin could represent a new treatment for patients to protect the brain against stroke’s potentially life-threatening effects, said Cheung, who is based at Queen Mary Hospital in Hong Kong.
But Cheung cautioned that people should not believe that they are no longer in danger of stroke if they buy melatonin, which is commercially available.
Too many questions remained unanswered, he said, including how best to use the hormone against stroke in humans, and whether it even works in people. Many treatments that are successful in rats and mice never pan out for their human counterparts.
“Therefore, taking the usual oral dosage of melatonin may not affect (a person’s) chance of having a stroke, nor the severity of the stroke, Cheung said.
Melatonin is a hormone that is produced by the pineal gland in the brain when the body is exposed to light.
Previous research has shown the hormone can promote sleep and help regulate the body clock. Because melatonin is believed to help regulate sleep patterns, supplements have been touted as a treatment for sleep problems and jet lag.
Recently, investigators have uncovered evidence that the hormone may also protect the brain from stroke.
To investigate further, Cheung and his colleagues blocked blood flow in an artery feeding the brain — the most common cause of stroke — for three hours in a group of rats.
In one experiment, the researchers injected the rats with a single dose of melatonin either immediately, one hour, or three hours later.
In another experiment, the researchers injected rats with multiple doses of the same amount of melatonin, with the first dose occurring within three hours of stroke onset, and additional doses 24 and 48 hours later.
In the first experiment, Cheung and his colleagues found that one dose of melatonin decreased the amount of brain tissue damaged by stroke when administered immediately or one hour after stroke, but not three hours later.
In the second experiment, the authors found that multiple melatonin injections helped reduce the amount of brain tissue damage after stroke, relative to rats that received injections that did not contain the hormone, but only when the first injection was administered within two hours.
Much of the damage inflicted by stroke results from an overproduction of free radicals, particles that can inflict serious tissue damage, Cheung explained.
Melatonin is a potent scavenger of free radicals, a role that largely explains the hormone’s benefits in treating stroke, Cheung noted. “This is the main reason why melatonin protects the brain against stroke,” he said.
The next step, Cheung noted, is to investigate whether melatonin safely works in humans, and if so, how it should be administered.
“One needs to show that an oral or injectable preparation of melatonin can achieve an effective concentration in the blood of stroke patients, and the dose is safe in stroke patients before one can conduct clinical trials on its efficacy,” he said.
Funding for the current research was provided by the University of Hong Kong.
– Source: Reuters Health
