Rats Necessary in Tinnitus Research—Teach Us About Working of Brain

I have tinnitus, not a huge problem—but irritating.  How would you like to be in the Tetons on a beautiful day and want to “listen” to the silence—and all you perceive is annnoying high-pitched squeal?  Sometimes, it’s two toned.  Sometimes my ears “hear” different tones.  Like I said, not a big deal.  I wouldn’t say I “suffer” from it.  My life is not deleteriously impacted.

Not true for others, however.  People with serious tinnitus lose sleep.  It can get so bad, that it drives some people to near distraction.  So, I was heartened to read that scientists may be on the trail of an effective treatment. From the story:

There is currently no cure for tinnitus, which can range from annoying to debilitating and affects as many as 23 million adults in the United States, including one in 10 seniors and 40 percent of military veterans.  For Gloria Chepko, 66, who has suffered from tinnitus since she was four years old, the sound she describes as “like crickets…  but also bell-like,” gets worse when she is tired. “It’s awful,” she said. “Sometimes it is very loud, and it will get loud if I am under stress or if I have been going for a very long time and I am fatigued,” she said. “If my mind is tired and I sit down I will only hear this sound.”

For some people, such as military veterans who are left with hearing damage after exposure to loud blasts and gunfire, the noise — which could also sound like roaring, whooshing or clicking — interferes with their ability to lead a normal life. The US Veterans Administration spends one billion dollars per year on disability paymentsAfghanistan, related to tinnitus, the most common service-related ailment in soldiers returning from Iraq and industry experts say.

But thanks to animal research on rats, scientist may have found a way to “reboot” the brain and teach it not to hear the squeal:

Scientists believe the disorder is caused by hearing loss or nerve damage, to which the brain tries but fails to adjust. “Brain changes in response to nerve damage or cochlear trauma cause irregular neural activity believed to be responsible for many types of chronic pain and tinnitus,” said Michael Kilgard of the University of Texas, “We believe the part of the brain that processes sounds — the auditory cortex — delegates too many neurons to some frequencies, and things begin to go awry,” he said. co-author of the study in the journal Nature.

To fix that, researchers used rats to test a theory that they could reset the brain by retraining it so that errant neurons return to their normal state. In rats with tinnitus, they electrically stimulated the vagus nerve, which runs from the head through the neck to the abdomen, in combination with playing a certain high-pitched tone.

When stimulated, the nerve can encourage changes in the brain by releasing chemicals such as acetylcholine and norepinephrine that act as neurotransmitters. Rats that underwent the pairing of noise and stimulation experienced a halt to the ringing sounds for up to three and a half months, while control rats that received just noise or just stimulation did not. An examination of neural responses in the auditory cortexes showed normal levels in the rats who were treated with the combination of stimulation and sound, indicating the tinnitus had disappeared. The treatment “not only reorganized the neurons to respond to their original frequencies, but it also made the brain responses sharper,” the study said. “The key is that, unlike previous treatments, we’re not masking the tinnitus, we’re not hiding the tinnitus,” said Kilgard.

Like I said, this isn’t cancer.  But I think this research is worthy of using the rats.  We are learning more about how the brain works.  It could lead to treatments for human maladies beyond tinitus.  Just a small example of why animal research is necessary to increasing biological knowledge and improving the human condition.