Effect of Different Doses of Atipamezole on Reversal of Medetomidine-Induced Tear-Flow Decrease in Rats

• Main Authors: Teppei Kanda, Manami Gotoh, Ayumi Makino, Kayo Furumoto, Yuki Shimizu, Takamasa Itoi, Noritaka Maeta, Toshinori Furukawa
• Format: Article
• Language: English
• Published: MDPI AG 2020-12-01
• Series: Veterinary Sciences
• Subjects: α₂-adrenoceptor agonist; medetomidine; atipamezole; tear flow; rat
• Online Access: https://www.mdpi.com/2306-7381/7/4/197

It has been reported that α₂-adrenoceptor agonists such as medetomidine decrease tear flow in many species, including rats. Few studies have investigated the involvement of α₂-adrenoceptor in decreased tear flow; the issue has not been illustrated sufficiently. Therefore, we aimed to investigate the effect of different doses of atipamezole on the reversal of medetomidine-induced tear-flow decrease to reveal the specific involvement of α₂-adrenoceptor. Treatment with 400, 800, or 1600 µg/kg atipamezole (or saline as the control) was intramuscularly administered to rats 15 min following intramuscular administration of 200 µg/kg medetomidine. After medetomidine administration, tear flow was measured using a phenol red thread test (PRTT). PRTT values decreased significantly after 200 µg/kg medetomidine administration. The PRTT values after 800 (optimal dose to reverse) and 1600 µg/kg atipamezole administration reached baseline, but never exceeded it significantly. Treatment with 400 µg/kg atipamezole also reversed the decrease in PRTT value but the PRTT remained lower than baseline. The optimal dose and the higher dose of atipamezole fully reversed the medetomidine-induced decrease in tear flow to the baseline level in rats, while the lower dose of atipamezole partially recovered tear flow.