The same genes that let smokers sleep without nicotine cravings may lead to methods to help them quit.Smokers, even those heavily addicted to nicotine, can usually sleep through the night without constantly waking up to light up another gasper. A researcher at the University of Colorado’s Institute for Behavioral Genetics is learning why this is so. What is it about sleep that reduces these cravings?
Conducting a study with mice, CU professor Jerry Stitzel found that the reduced effects of nicotine at night were dependent on the mice’s genetic makeup, and whether their brains and bodies were able to recognize melatonin, a powerful hormone and antioxidant that is produced at night by the body. Melatonin is produced in the brains pineal gland, and it helps regulate the human circadian cycle – our daily day/night rhythms – and can cause drowsiness. In concert with other body system, melatonin tells us when to sleep.
“I wanted to answer the question, `Why is it that smokers can sleep through the night without constantly waking with cravings?'” Stitzel said. “Smokers smoke cigarettes during the day to maintain a specific level of nicotine in the body. As soon as they wake up, they smoke to ramp up the amount of nicotine in their blood. Then they maintain it during the day.”
Stitzel said a previous study, which he wasn’t involved in, found that people who were trying to quit smoking were given melatonin, which reduced their nicotine craving in people who were trying to quite smoking. “That was one of the reasons I did the study,” he said. “Melatonin does alter the effects of nicotine. We don’t know why it is altering it, but it does.”
In his mouse study, Stitzel looked at two different sets of genes. When the genes prevented the mice from recognizing the melatonin, their sensitivity to nicotine was not altered either. In other words, the brain has to be able to recognize melatonin before it can respond by reducing the nicotine cravings. Humans have the same genes.
“The depth of a person’s addiction to nicotine appears to depend on his or her unique internal chemistry and genetic makeup,” he said.
The next step is to figure out what areas of the brain are changing the mice’s response to nicotine, he said. “Once we grasp the reason they are responding, from there we might be able to think about developing more treatments,” Stitzel said.
One possibility would be to find a drug that stimulates the activity of the melatonin-recognizing gene. “But we don’t want to mess around in that too much,” Stitzel said, “because it is also responsible for regulating our normal circadian rhythm. We have to get around the melatonin and get further down in the brain to message it is trying to tell us.”
