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 SIGNIFICANCE STATEMENTNicotine 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.

Alcohol use disorders (AUDs) are a major problem across the United States. While AUD remains a complex human condition, it is difficult to isolate the directionality of anxiety and ethanol (EtOH) drinking from outside influences. The present study sought to investigate the relationship between affective states and EtOH intake using male and female Sprague Dawley rats. Using complementary tests of anxiety- and depressive-like behavior, we found sex- and test-specific differences in basal affective behavior such that females displayed enhanced anxiety-like behavior in the Splash Test and males displayed enhanced anxiety-like behavior in the Novelty Suppressed Feeding Test. Although there were no sex differences in EtOH intake and no correlation between anxiety-like behavior and subsequent EtOH intake, we did find that depressive-like behavior predicted future EtOH intake in females rats only. In addition, we observed an increase in depressive-like behavior is male rats in both the water and EtOH drinking groups. Furthermore, anxiety-like behavior, but not depressive-like behavior predicted subsequent EtOH intake in female rats. Lastly, we found a history of EtOH intake decreased pain thresholds in male and female rats. Together, these experiments provide important information on the complex interaction between negative affect and alcohol intake and how these two contexts reciprocally do, or do not, influence each other in a sex-specific manner.

Alcohol use disorders (AUDs) are a major problem across the United States. While AUD remains a complex human condition, it is difficult to isolate the directionality of anxiety and ethanol (EtOH) drinking from outside influences. The present study sought to investigate the relationship between affective states and EtOH intake using male and female Sprague Dawley rats. Using complementary tests of anxiety-and depressive-like behavior, we found sex-and test-specific differences in basal affective behavior such that females displayed enhanced anxiety-like behavior in the Splash Test and males displayed enhanced anxiety-like behavior in the Novelty Suppressed Feeding Test. Although there were no sex differences in EtOH intake and no correlation between anxiety-like behavior and subsequent EtOH intake, we did find that depressive-like behavior predicted future EtOH intake in females rats only. In addition, we observed an increase in depressive-like behavior is male rats in both the water and EtOH drinking groups. Furthermore, anxiety-like behavior, but not depressive-like behavior predicted subsequent EtOH intake in female rats. Lastly, we found a history of EtOH intake decreased pain thresholds in male and female rats. Together, these experiments provide important information on the complex interaction between negative affect and alcohol intake and how these two contexts reciprocally do, or do not, influence each other in a sex-specific manner.

Nicotine engages dopamine neurons in the ventral tegmental area (VTA) to encode reward and drive the development of nicotine addiction, however how nicotine alters a stress associated VTA population remains unclear. Here, we used male and female CRF1-GFP mice and nicotine vapor exposure to examine the effects of nicotine in VTA corticotropin-releasing factor receptor 1 (CRF1) neurons. We use immunohistochemistry and electrophysiology to examine neuronal activity, excitability, and inhibitory signaling. We found that VTA CRF1 neurons are mainly dopaminergic and project to the nucleus accumbens (VTA-NAcCRF1 neurons).VTA-NAcCRF1 neurons show greater phasic inhibition in naïve females and greater focal nicotine-induced increases in firing in naïve males. Following acute nicotine vapor exposure, phasic inhibition was not altered, but focal nicotine-induced tonic inhibition was enhanced in females and diminished in males. Acute nicotine vapor exposure did not affect firing inVTA-NAcCRF1 neurons, but females showed lower baseline firing and higher focal nicotine-induced firing. Activity (cFos) was increased in the CRF1 dopaminergic VTA population in both sexes, but with greater increases in females. Following chronic nicotine vapor exposure, both sexes displayed reduced basal phasic inhibition and the sex difference in tonic inhibition following acute vapor exposure was no longer observed. Additionally, activity of the CRF1 dopaminergic VTA population was no longer elevated in either sex. These findings reveal sex- and exposure-dependent changes in mesolimbic VTA-NAc CRF1 neuronal activity, inhibitory signaling, and nicotine sensitivity following nicotine vapor exposure. These changes potentially contribute to nicotine-dependent behaviors and the intersection between stress, anxiety, and addiction.SIGNIFICANCE STATEMENT:Nicotine is known to engage reward systems in the brain historically centering the neurotransmitter dopamine however, how nicotine impacts other neurons in the reward pathway is less clear. The current study investigates the impact of acute and chronic electronic nicotine vapor exposure in a genetically-defined cell population containing the stress receptor corticotropin releasing factor 1 (CRF1) that is located in the reward circuitry. This study employs functional measures of neuronal activity and identifies important sex differences in nicotine’s effects across time and exposure.

Nicotine engages dopamine neurons in the ventral tegmental area (VTA) to encode reward and drive the development of nicotine addiction, however how nicotine selectively alters other VTA populations remains to be determined. Here, we used male and female CRF1-GFP mice and nicotine vapor exposure to examine the effects of nicotine in VTA corticotropin-releasing factor receptor 1 (CRF1) neurons. We use immunohistochemistry and electrophysiology to examine neuronal activity, excitability, and inhibitory signaling. We found that VTA CRF1 neurons are mainly dopaminergic and project to the nucleus accumbens (VTA-NAcCRF1 neurons). VTA-NAcCRF1 neurons show greater phasic inhibition in naive females and greater focal nicotine-induced increases in firing in naive males. Following acute nicotine vapor exposure, phasic inhibition was not altered, but focal nicotine-induced tonic inhibition was enhanced in females and diminished in males. Acute nicotine vapor exposure did not affect firing in VTA-NAcCRF1 neurons, but females showed lower baseline firing and higher focal nicotine-induced firing. Activity (cFos) was increased in the CRF1 dopaminergic VTA population in both sexes, but with greater increases in females. Following chronic nicotine vapor exposure, both sexes displayed reduced basal phasic inhibition and the sex difference in tonic inhibition following acute vapor exposure was no longer observed. Additionally, activity of the CRF1 dopaminergic VTA population was no longer elevated in either sex. These findings reveal sex- and exposure-dependent changes in mesolimbic VTA-NAc CRF1 neuronal activity, inhibitory signaling, and nicotine sensitivity following nicotine vapor exposure. These changes potentially contribute to nicotine-dependent behaviors and the intersection between stress, anxiety, and addiction.