Serotonin May Worsen Tinnitus

Serotonin May Worsen Tinnitus

Summary: Researchers report fusiform cells in the dorsal cochlear nucleus become hyperstimulated when exposed to serotonin. Findings could have implications for those taking SSRIs as they may make tinnitus worse in some people.

Source: OHSU.

Millions of people suffer from the constant sensation of ringing or buzzing in the ears known as tinnitus, creating constant irritation for some and severe anxiety for others. Research by scientists at OHSU shows why a common antidepressant medication may worsen the condition.

The study, to be published Aug. 22 in the journal Cell Reports, focused on the action of serotonin, an important neuromodulator in the brain. Researchers examined brain tissue in mice, specifically the dorsal cochlear nucleus where sensory integration and tinnitus occurs. Researchers discovered that neurons known as fusiform cells within this portion of the brain become hyperactive and hypersensitive to stimuli when exposed to serotonin.

“We saw that the activity of those neurons went through the roof,” said senior author Laurence Trussell, Ph.D., a professor of otolaryngology in the OHSU School of Medicine and scientist in the OHSU Vollum Institute.

If the findings bear up to additional research, the study could have implications for a common class of antidepressants known as selective serotonin reuptake inhibitors (SSRI). SSRIs can alleviate symptoms of moderate to severe depression and anxiety by increasing the level of serotonin in the brain. Serotonin is a chemical compound that acts as a neurotransmitter thought to be responsible for maintaining mood balance.

However, the research suggests that SSRIs prescribed to treat anxiety or depression may sometimes worsen patients’ tinnitus. Tinnitus is defined as the chronic perception of sound when there is no internal or external acoustic source.

“If you’re a physician treating a patient for depression who also has hearing loss or tinnitus, you may want to be careful about prescribing a drug that compounds their feelings of anxiety,” said Trussell, who also suffers from tinnitus and, in addition to his other roles, has an appointment in the Oregon Hearing Research Center at OHSU. “The SSRI may be enhancing the thing you’re trying to fix.”

Lead author Zheng-Quan Tang, Ph.D., a senior postdoctoral fellow in Trussell’s lab, noted that a review of existing scientific literature indicated that many patients reported an increase in tinnitus soon after they began taking SSRIs.

Image shows a stick and ball model of serotonin.

“Estimates vary, but at least 10 percent of the U.S. population is affected by tinnitus,” Tang said.

The OHSU scientists are interested in exploring another area of research focused on a type of ion channel in the membrane of neurons that is activated by serotonin. If the scientists can determine a way to deactivate those channels, they may be able to allow the beneficial effects of antidepressants while limiting the severity of tinnitus.

ABOUT THIS NEUROSCIENCE RESEARCH ARTICLE

Funding: The study was supported by the Hearing Health Foundation and National Institutes of Health grants NS028901 and DC004450.

Source: Erik Robinson – OHSU
Image Source: NeuroscienceNews.com image is in the public domain.
Original Research: The study will appear in Cell Reports.

OHSU “Serotonin May Worsen Tinnitus.” NeuroscienceNews. NeuroscienceNews, 22 August 2017.
<http://neurosciencenews.com/tinnitus-serotonin-7348/&gt;.

Risk Factors of Pancreatic Cancer

Risk Factors of Pancreatic Cancer

The causes of pancreatic cancer are not fully understood. However, certain personal, environmental, health, and inherited risk factors have been identified that increase the chances of a person developing the disease.

Personal Risk Factors

  • Age: The risk of developing pancreatic cancer increases after age 50. Most patients are between the ages of 60 and 80 at the time of diagnosis.
  • Ethnicity: There is higher incidence of pancreatic cancer in Ashkenazi Jews, probably due to common genetic mutations present in at least 1% of individuals of this background. African Americans are also more likely to develop pancreatic cancer than are Asians, Hispanics, and Caucasians. The reasons for this discrepancy are not known but may be related to differences in other risk factors and habits like diet and cigarette smoking frequency.

Environmental Risk Factors

  • Cigarette Smoking: About 30% of pancreatic cancer cases are thought to be a direct result of cigarette smoking. People who smoke cigarettes are twice as likely to develop pancreatic cancer as people who do not smoke cigarettes. Additionally, the cancerous tumors that form as a result of cigarette smoking grow at an accelerated rate and develop approximately 10 years earlier than tumors not related to smoking.

Health Risk Factors

  • Chronic Pancreatitis: Pancreatitis is an inflammation of the pancreas. People diagnosed with chronic pancreatitis have an increased risk of developing pancreatic cancer. Chronic pancreatitis is a condition that can strike people of any age. It is typically diagnosed in people who are 35-45 years old. It can be due to a number of factors including hereditary (genetic) pancreatitis, malformation of pancreas ducts, trauma to pancreas, or excessive alcohol abuse for many years. Click here for more information on pancreatitis.
  • Diabetes: Pancreatic cancer is two times more likely to occur in people who have diabetes than in people who do not have diabetes. However, the relationship between diabetes and pancreatic cancer is still not completely understood. It is not uncommon for individuals to develop diabetes before pancreatic cancer is detected and it may be that this glucose intolerance is actually caused by changes in the pancreas resulting from the cancer.
  • Weight: The body mass index (BMI) is a statistical measure calculated based on a person’s height and weight. A person with a BMI above 25 is considered overweight and this can increase the risk of developing pancreatic cancer.

Inherited Risk Factors

  • Inherited Risk: Up to 15% of pancreatic cancer is related to a family history of the disease. The risk of developing pancreatic cancer increases by 2-3 times if a person’s mother, father, sibling, or child had pancreatic cancer. The risk multiplies if a greater number of family members are affected. There are several inherited gene mutations that have been linked to an increased risk of pancreatic cancer including the genes responsible for breast and ovarian cancer, and melanoma. Learn more about the specific genetic conditions, including a BRCA gene mutation, that lead to an increased risk for pancreatic cancer.