Caffeine inhalation effects on locomotor activity in mice

Abstract

It is estimated that 80% of the world’s population consumes caffeine from beverages and food every day. The traditional form of caffeine intake is oral, but more recently people have been inhaling caffeine using nasal sprays. However, the effects of caffeine inhalation are not well understood. The purpose of this study was to determine whether caffeine inhalation affects mouse behavior. To test this, we compared spontaneous activity of mice following inhalation and intraperitoneal administration of caffeine. Next, we investigated whether spontaneous activity changed with the time and/or concentration of caffeine inhaled. We found that mice that inhaled caffeine increased their spontaneous activity similar to mice that were administered caffeine intraperitoneally. Furthermore, spontaneous activity increased in an inhalation time-dependent and concentration-dependent manner. These results show that caffeine-induced stimulation also occurs by inhalation in mice, which suggests that caffeine can reach the brain even by inhalation. This study is useful not only for creating new administration methods of caffeine but also for adjusting caffeine storage and management.

Keywords:

• Spontaneous activity
• behavior
• caffeine inhalation
• mouse
• locomotion

Acknowledgments

The authors thank the Kawasaki Medical School Central Research Institute for providing instruments to support this study. The authors also thank Editage (www.editage.jp) for English language editing.

Disclosure statement

The authors declare that there are no conflicts of interest.

Author contributions

All authors had full access to all study data and take full responsibility for the integrity of the data and the accuracy of the data analysis. HU, MO, and TI developed the concept and design of the study. HU, YT, and SS acquired, analyzed, and interpreted the data. HU and MO drafted the manuscript. SM, NK, KW, YM, and TI performed critical revisions of the manuscript for important intellectual content. MO and TI supervised the study.

Availability of data and materials

All relevant data are within the manuscript.

Additional information

Funding

This work is supported by a Grant Aid for the Yakumo Foundation for Environmental Science and the Toyo Suisan Foundation.