Veterinary researchers: nicotine reduces stress, respiratory awareness

If that smoker next to you seems more relaxed than you, you might be right. UF veterinary researchers say smokers reduce stress because nicotine appears to mask the brain's awareness of outside stimuli, thereby reducing anxiety.

"Smoking may kill, but the stress-reducing effects of nicotine on the brain are probably one reason why the habit is so prominent among college students," said Paul Davenport, Ph.D., a professor in the University of Florida College of Veterinary Medicine's department of physiological sciences. "As many as 15 to 20 percent of college students are smokers, perhaps best exemplified by the phenomenon of social smoking. These students often ignore the deadly side effects in exchange for the trade-off of reduced anxiety."

Davenport is studying the effect of nicotine withdrawal on brain activity and cough in one of four projects UF veterinary researchers have been working on as part of a $1 million grant from the Florida Department of Health's James and Esther King Biomedical Research Program. Data from his study assessing how nicotine affects smokers' ability to sense their breathing will be presented in May at the American Thoracic Society meeting.

"Chronic obstructive pulmonary disease is a common problem with smokers," Davenport said. "Both animals and humans can have COPD. The motivation to seek treatment is directly related to the patient's cognitive awareness of their breathing status."

His study measured how respiratory stimuli are controlled by higher brain centers responsible for thinking, reasoning and problem-solving. Davenport found that individuals who are withdrawing from smoking become more aware of their breathing and may even become fearful, especially if their airway becomes obstructed.

"When you have individuals that abstain from smoking for a 12-hour period, they get very agitated," Davenport said. "This is because while they are smoking, smokers' brain activity is 'gated,' or controlled. Nicotine is useful because it reduces anxiety, but it also helps mask certain brain activity, so that if you withdraw from nicotine you are much more sensitive to stimuli coming in."

Other research efforts, spearheaded by Donald Bolser, Ph.D., and Linda Hayward, Ph.D., from the veterinary college and David Fuller, Ph.D., from UF's College of Public Health and Health Professions, are examining the effects of nicotine on everything from sleep patterns to newborns exposed in the womb. In future studies, Davenport plans to examine how nicotine affects the brain pathways that lead to consciousness.

"You don't constantly think about breathing, but when something changes, you become aware of it," Davenport said. "With smoking, your lungs change, but you're not aware of it. It's awareness of one's internal environment that we are most interested in."

In a related study with Bolser, whose expertise is in the cough reflex, Davenport has used capsaicin - the hot ingredient in hot peppers - to induce the urge to cough. He and Bolser are interested in why smokers don't cough in response to inhaling cigarette smoke, but non-smokers do.

"This sensation of the need to cough comes before you actually cough, which allows our consciousness to interact with the cough reflex," Davenport said. "If you're in a concert and you feel the need to cough, you have the ability to suppress that cough by conscious mechanisms.

"That's why it's important that your brain knows your need to cough before you actually cough," he added. "Nicotine is changing the way the brain functions, probably by changing the way respiratory sensations are gated into the conscious regions of the brain."

Bolser said studies of the relationship between the urge-to-cough sensation and the behavior associated with it are new and a "big deal" in the field of respiratory disease research.

"The people in our field of cough research really didn't think about the sensations associated with the behavior and how the behavior is produced," Bolser said. "The urge to cough is a sensation we now know exists and now we are thinking about the relevance of the urge to how the nervous system generates behavior and how this might be a factor in how cough suppressants work."

Davenport said it's clear that if breathing is obstructed in either animals or humans, tremendous fear and anxiety occur, and in many cases, humans experience a full-blown anxiety attack.

"What is it about disordered breathing that makes us so fearful, and what can we do to help patients and animals that have these tremendous fear responses to disordered breathing?" Davenport asks. "Clinically, we need to treat the lung disease, but what we seldom treat is the anxiety the patient has related to their lung disease."

Anyone with COPD understands the feeling of breathlessness even upon such activity as walking through a mall, or mild exercise. Because of this, many people with COPD become less and less active, Davenport said.

"When we fear we won't be able to breathe, we won't exercise," he said. "So if we can figure out how to lessen the anxiety of those who suffer from COPD, we can improve their rehabilitation from lung disease."

And as for those college students who smoke - don't look for their habits to change anytime soon.

"The use of nicotine to self-medicate for stress has serious side effects, produces deadly disease and is extremely addictive," Davenport said. "When I talk to young people, I tell them, 'You will get lung and heart disease; smoking will kill you.' But we have to recognize that even with that knowledge, kids still smoke because they feel the benefits exceed the risks."