The George Lab published a new study investigating electronic cigarette use. The main goal of the study was to validate a new pre-clinical model of nicotine vapor self-administration with anatomical and behavioral characterization of dependence. We examined the effects of chronic nicotine vapor intake on key behaviors that are related to nicotine withdrawal in male and female rats, including hyperalgesia, somatic signs, and anxiety-like behavior.
Our data showed that two weeks of nicotine vapor self-administration was sufficient to make the rats dependent, reflected by increased somatic signs of withdrawal, and decreased pain thresholds precipitated by mecamylamine. A separate group of rats self-administering vehicle vapor showed no signs of dependence after the same treatment. Decreased pain thresholds persisted three weeks into abstinence from nicotine vapor, at which point increased anxiety- and relapse-like behavior was also observed.
Our study also tested whether chronic nicotine vapor self-administration would produce long-term cardiopulmonary abnormalities. Our results showed that rats with a history of nicotine vapor use had increased alveolar simplification and decreased heart weight and length three weeks into abstinence. We also observed changes in nicotinic acetylcholine receptor expression during three weeks of abstinence. These effects were not observed in rats without nicotine exposure. These findings suggest electronic cigarette use could cause cardiopulmonary abnormalities and changes in brain cholinergic receptor expression that persist even after cessation. Remaining to be determined in future studies are the effects of vapor on nicotine reward and discrimination and the effects of flavorings on electronic cigarette use.