The Effect of Vapor of Propylene Glycol on Rats

• Published in: Chemical senses 2010-03, Vol.35 (3), p.221-228
• Main Authors: Inagaki, Hideaki, Taniguchi, Mutsuo, Muramoto, Kazuyo, Kaba, Hideto, Takeuchi, Yukari, Mori, Yuji
• Format: Article
• Language: English
• Subjects: acoustic startle reflex; Animals; aversive stimulus; Biological and medical sciences; Calcium - metabolism; calcium imaging; Fundamental and applied biological sciences. Psychology; Gases - chemistry; habituation/dishabituation test; Male; non-pheromonal odorant; olfaction; Olfaction. Taste; Perception; Propylene Glycols - pharmacology; Psychology. Psychoanalysis. Psychiatry; Psychology. Psychophysiology; Rats; Rats, Wistar; Sensory Gating - physiology; Vomeronasal Organ - drug effects; Vomeronasal Organ - physiology
• ISSN: 0379-864X; 1464-3553
• DOI: 10.1093/chemse/bjp104

Propylene glycol (PG) is commonly used as a solvent for odorous chemicals employed in studies of the olfactory system because PG has been considered to be odorless for humans and other animals. However, if laboratory rats can detect the vapor of PG and if exposure to this influences behaviors, such effects might confound data obtained from experiments exposing conscious rats to odorants dissolved in PG. Therefore, we examined this issue using differences in the acoustic startle reflex (ASR) as an index. We also conducted a habituation/dishabituation test to assess the ability of rats to detect the vapor of PG. In addition, we observed Ca2+ responses of vomeronasal neurons (VNs) in rats exposed to PG using the confocal Ca2+-imaging approach. Pure PG vapor significantly enhanced the ASR at a dose of 1 × 10−4 M, which was much lower than the dose for efficiently detecting. In Ca2+ imaging, VNs were activated by PG at a dose of 1 × 10−4 M or lower. These results suggest that PG vapor acts as an aversive stimulus to rats at very low doses, even lower than those required for its detection, indicating that we should consider such effect of PG when it is employed as a solvent for odorants in studies using conscious rats. In addition, our study suggests that some non-pheromonal volatile odorants might affect animal behaviors via the vomeronasal system.