A new study on the effect of ketamine, a pain-relieving drug used in anesthesia procedures, has enabled the detection of unprecedented effects of ketamine on the brain.
Scientists from the University of Cambridge revealed new information on how different doses of ketamine applied to sheep during their research on Huntington’s disease in sheep.
The most striking result of the study was the complete disappearance of brain activity in EEG scans performed after sheep were given high doses of ketamine. Sheep whose brain activity could not be screened showed activity again in EEG scans a few minutes after the drug was given.
“This is not just a reduction in brain activity,” says neurobiologist Jenny Morton, who explains the study. After the high dose of ketamine, the brains of the sheep completely stopped. We’ve never seen this before. A few minutes later his brains started working normally again. It was as if it was closed and opened. ”
Ketamine has been used in anesthesia since 1960
Synthesized for the first time in 1960, ketamine has been used as a pain reliever for decades. Ketamine is also used as a sedative in both humans and animals. The drug has also given promising results in the treatment of various conditions such as depression, post-traumatic stress disorder and migraine in recent years.
The purpose of the study of scientists was to investigate how therapeutic drugs affect the brains of sheep with Huntington’s disease. However, the brain activities of the sheep with EEG devices implanted in the skulls were also recorded during the research.
The main purpose of the study was not to investigate the effects of ketamine.
Jenny Morton said that their main goal was not to look at the effects of ketamine, but to investigate brain activity in sheep with and without Huntington’s disease gene. “But our surprising findings can help explain how ketamine works,” said Morton.
During the study, sheep were given between 3mg / kg (3 milligrams of ketamine per kilogram of body weight) and 24mg / kg of ketamine. Regardless of the doses given to the animals, three separate stages of activity were recorded: the sedation stage after the drug was administered, the still and unconscious stage, and the full alertness stage, although there was still no movement.
In the second phase, which occurred after sedation, scientists identified an alternative oscillation state while performing brain scans. The output of the entire brain cortex during oscillation here varied between low and high frequency oscillation bursts.
EEG activities of sheep with high doses of ketamine stopped completely
When the researchers gave the high dose of 24mg / kg ketamine to the sheep, an unprecedented response occurred. EEG activities completely stopped in 5 of 6 sheep that received high doses of ketamine. Scientists have called this unprecedented reaction the EEG hole.
It was stated in the published results of the study that this effect was observed for the first time. “It seems that the complete cessation of cortical activity is the basis for what is known as the K-hole,” the article said.
Jenny Morton said that the reaction called EEG hole does not necessarily mean that all the brain activity of the animals has stopped. Morton said that if all brain activity had stopped, animals should stop breathing. “Instead, the falling EEG reading reflects that the usual electrical activity that we can detect in the brain under normal circumstances stops very strangely,” Morton said.
Although the activity in the cortex of the sheep that received ketamine stopped completely for a short time, the brains of the sheep did not die during this process or received any damage. Within a few minutes, the EEG hole effect disappeared and the sheep continued to show brain activity consistent with the phases of the drug, as in sheep with low doses of ketamine.
Although the scientists who conducted the study did not know how ketamine produced the unusual activity that the brain produced in the brain, they said their research would help to learn more about how the brain works as a whole.
The researchers explained that understanding how ketamine interacts with brain regions and how it separates from those brain regions will be key to understanding the function of neural networks. Changes resulting from the effects of ketamine observed in EEG can provide a tool to study neural networks that cause neurological diseases to occur.