2-B-P-044 〇林田 健一郎、森 大輝、堀本 泰弘、沼田 洋輔 Kenichiro Hayashida, Daiki Mori, Yasuhiro Horimoto, Yosuke Numata 新日本科学・薬効薬理研究部 Dept. Pharmacology. Shin Nippon Biomedical Laboratories, Ltd. The measurement of tail withdrawal latencies to thermal stimuli has been a predominant behavioral assay for analgesic efficacies of drugs in non-human primates. Nevertheless, there are two major concerns. One is to evaluate analgesia using the tail, which is not present in humans, and the other is the presence of individual variations in the motor function of the tail. The present study performed the thermal probe test in 8 male cynomolgus monkeys (6-8 years old) to examine thermal nociception and capsaicin-induced thermal hypersensitivity in the dorsal hind paws (DHPs). Thermal stimuli (cutoff: 60℃) applying to the DHPs increased by 1℃ per second starting from 35℃ and paw withdrawal temperature (PWT) was recorded when the animal withdrew the hind paw. Buprenorphine (0.01 and 0.05 mg/kg i.m.), morphine (1 and 3 mg/kg i.m.) and medetomidine (0.02 and 0.1 mg/kg i.m.) dose-dependently increased PWT, indicating their analgesic efficacies. Topical application of 1% capsaicin to the DHPs resulted in a reduction in PWT, and this capsaicin-induced thermal hypersensitivity was reversed by buprenorphine and medetomidine. These results demonstrate the value of PWT measurements in DHPs for assessing pain and the efficacies of analgesics in cynomolgus monkeys.