Electronic nicotine vapor exposure produces differential changes in central amygdala neuronal activity, thermoregulation and locomotor behavior in male mice

Abstract

Nicotine is an addictive substance historically consumed through smoking and more recently through the use of electronic vapor devices. The increasing prevalence and popularity of vaping prompts the need for preclinical rodent models of nicotine vapor exposure and an improved understanding of the impact of vaping on specific brain regions, bodily functions, and behaviors. We used a rodent model of electronic nicotine vapor exposure to examine the cellular and behavioral consequences of acute and repeated vapor exposure. Adult male C57BL/6J mice were exposed to a single 3 hour session (acute exposure) or 5 daily sessions (repeated exposure) of intermittent vapes of 120 mg/ml nicotine in propylene glycol:vegetable glycerol (PG/VG) or PG/VG control. Acute and repeated nicotine vapor exposure did not alter body weight and both exposure paradigms produced pharmacologically significant serum nicotine and cotinine levels in the 120 mg/ml Nicotine group compared to PG/VG controls. Acute exposure to electronic nicotine vapor increased central amygdala (CeA) activity in individual neuronal firing and in expression of the molecular activity marker, cFos. The changes in neuronal activity following acute exposure were not observed following repeated exposure. Acute and repeated nicotine vapor exposure decreased core body temperature, however acute exposure decreased locomotion while repeated exposure increased locomotion. Collectively, these studies provide validation of a mouse model of nicotine vapor exposure and important evidence for how exposure to electronic nicotine vapor produces differential effects on CeA neuronal activity and on specific body functions and behaviors like thermoregulation and locomotion.

SIGNIFICANCE STATEMENT

Nicotine vaping is increasing, prompting the need for an improved understanding of the impact of electronic nicotine vapor exposure on specific brain regions and relevant physiological functions and behaviors. The present study used a mouse model of nicotine vapor exposure to examine the cellular and behavioral consequences of acute and repeated exposure to nicotine vapor. We found that acute, but not repeated, exposure to nicotine vapor increased activity in the central amygdala and that acute and repeated exposure produced differential effects on body temperature and movement. These findings demonstrate that nicotine vaping alters brain function in the central amygdala and produces dysregulation of normal body functions like thermoregulation and locomotion.