The disturbances of menthol sensitivity in a prodromal Parkinson's disease model mice with intranasal rotenone

Abstract

Parkinson’s disease (PD) causes taste impairments as well as impaired senses of smell since the early-stage. We previously reported that bitter taste impairments may occur simultaneously, but independently, with olfactory impairments in a prodromal animal model of PD. Cool/cold temperature also affects the perception of bitter taste, but it remains unclear whether bitter taste impairments in this animal model result from altered cool/cold sensitivity. We examined the changes in the menthol sensitivity, such as coolness/irritation at low/high concentrations of menthol, in 1-week intranasal rotenone-administrated mice using brief-access or 48-hour 2-bottle tests. The total number of licks during the 20 trials of 10 sec in rotenone-treated mice showed a significant increase at 2.3 mM menthol compared to the data obtained before the rotenone treatment. In 2-bottle tests, mice after rotenone treatment showed a higher aversion to menthol compared to before. Interestingly, rotenone-treated mice significantly preferred 200 μg/mL nicotine solution to that with 100 μg/mL menthol. The disturbances of the menthol sensitivity in 1-week intranasal rotenone-administrated mice may be induced by the impairment of not only transient receptor potential (TRP) ankyrin 1 channel, but also TRP melastatin 8.