Evaluation of Flavor Effects on Oral Nicotine Liking and/or Disliking Using the Taste Reactivity Test in Rats

Neural modulation by nicotine aerosols and the role of flavor additives: insights from local field potentials in mice

Research on nicotine's neurobiological effects has rarely focused on aerosols, despite their primary role in tobacco product consumption. Here, we utilized in vivo electrophysiology to examine brain activity in mice exposed to nicotine aerosols, both alone and with flavor additives (citric acid and menthol). Local field potential (LFP) recordings from the nucleus accumbens (NAc), basolateral amygdala (BLA), ventral tegmental area (VTA), and ventral posteromedial nucleus (VPM) were analyzed under saline, nicotine, nicotine with citric acid(CA + NIC), and nicotine with menthol(MENT + NIC) conditions. Nicotine exposure significantly reduced power spectral density (PSD) in the NAc-Alpha, NAc-Beta, and BLA-Beta bands, unaffected by flavor additives. Coherence between key brain regions (e.g., VPM-VTA in Beta, VPM-BLA in Alpha) also decreased with nicotine but was restored with citric acid or menthol, suggesting their role in mitigating nicotine's disruptive effects on neural synchronization. Our findings show that LFPs can effectively capture nicotine's neural effects and highlight the modulatory role of flavor additives, offering new insights into nicotine exposure management and tobacco product design.

Impact of vanilla flavor on nicotine taste, choice, intake, and seeking behaviors

RATIONALE

Flavors can alter the orosensory properties of tobacco products. Specifically, flavors can serve as an oral cue for smokeless tobacco products.

OBJECTIVES

We aimed to investigate the impact of oral vanillin, the principal chemical of vanilla flavor in tobacco products, on nicotine's taste, and nicotine choice, intake, and seeking behaviors.

METHODS

Experiments were performed in young adult Sprague Dawley rats. We employed a two-bottle free-choice test (2BC) to measure the preference for different concentrations of vanillin and its effect on nicotine preference. To explore the long-term effects of early exposure to sweetened vanillin, we utilized a combined 2BC and intraoral self-administration (IOSA) model. We assessed the nicotine taking and seeking behaviors in the presence or absence of vanillin. We performed a taste reactivity test (TRT) to quantify liking (ingestive) and disliking (aversive) taste responses to oral nicotine with or without vanillin.

RESULTS

In 2BC, female rats preferred vanillin containing solutions more than their male counterparts. In IOSA, vanillin alone and in combination with nicotine led to greater IOSA compared to water. Female rats self-administered vanillin plus nicotine more than male rats. Vanillin increased motivation to nicotine taking, but only in females. In TRT, vanillin increased nicotine's ingestive responses but blocked aversive responses in both sexes.

CONCLUSIONS

These results indicate that vanilla flavor can increase oral nicotine intake. It can also increase liking and decrease disliking of nicotine's taste. Furthermore, the impact of vanilla flavor on nicotine taste and nicotine choice, intake, and seeking behaviors is concentration and sex dependent.

Chemosensory Contributions of E-Cigarette Additives on Nicotine Use

While rates of smoking combustible cigarettes in the United States have trended down in recent years, use of electronic cigarettes (e-cigarettes) has dramatically increased, especially among adolescents. The vast majority of e-cigarette users consume "flavored" products that contain a variety of chemosensory-rich additives, and recent literature suggests that these additives have led to the current "teen vaping epidemic." This review, covering research from both human and rodent models, provides a comprehensive overview of the sensory implications of e-cigarette additives and what is currently known about their impact on nicotine use. In doing so, we specifically address the oronasal sensory contributions of e-cigarette additives. Finally, we summarize the existing gaps in the field and highlight future directions needed to better understand the powerful influence of these additives on nicotine use.

Animal Models to Investigate the Impact of Flavors on Nicotine Addiction and Dependence

BACKGROUND

Tobacco use in humans is a long-standing public health concern. Flavors are common additives in tobacco and alternative tobacco products, added to mask nicotine's harsh orosensory effects and increase the appeal of these products. Animal models are integral for investigating nicotine use and addiction and are helpful for understanding the effects of flavor additives on the use of nicotine delivery products.

OBJECTIVE

This review focuses on preclinical models to evaluate the contribution of flavor additives to nicotine addiction.

MATERIALS AND METHODS

An electronic literature search was conducted by authors up to May 2022. Original articles were selected.

RESULTS

The behavioral models of rodents described here capture multiple dimensions of human flavored nicotine use behaviors, including advantages and disadvantages.

CONCLUSION

The consensus of the literature search was that human research on nicotine use behavior has not caught up with fast-changing product innovations, marketing practices, and federal regulations. Animal models are therefore needed to investigate mechanisms underlying nicotine use and addiction. This review provides a comprehensive overvie.