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Satoshi Sakakibara, Noritaka Imamachi, Manabu Sakakihara, Yukiko Katsube, Mai Hattori, Yoji SaitoDepartment of Anesthesiology, Shimane University Faculty of Medicine, Shimane, JapanCorrespondence: Noritaka ImamachiDepartment of Anesthesiology, Shimane University Faculty of Medicine, 89-1 Enyacho Izumo, Shimane693-8501, JapanTel +81 85 320 2295Fax +81 85 320 2292Email imamachi@med.shimane-u.ac.jpPurpose: Transient receptor potential vanilloid 1 (TRPV1) not only is activated by multiple stimuli but also is involved with histamine-induced itch. The effects of TRPV1 on morphine-induced itch are unknown. We examined the effects of intrathecal administration of TRPV1 antagonist on morphine-induced itch, body temperature, and antinociception for mice.Methods: Each C57/BL6j mouse was intrathecally administered with one of the following solutions: morphine, SB366791 (as the TRPV1 antagonist), morphine + SB366791, saline, or vehicle. For each mouse, each instance of observed scratching behavior was counted, the body temperature was measured, and the nociceptive threshold was determined using the tail-immersion test.Results: SB366791 dose-dependently reduced the scratching behavior induced by the administration of morphine. SB366791 and the morphine + SB366791 groups did not manifest an increase in body temperature. Antinociceptive effects were observed to occur dose-dependently for morphine but not for SB366791. Compared with morphine alone, the administration of morphine + SB366791 did not reduce significant antinociceptive effects.Conclusion: We propose that an intrathecal TRPV1 antagonist, SB366791, reduced morphine-induced itch without causing hyperthermia and did not suppress morphine-induced antinociception for mice.Keywords: pruritus, opioid, TRPV1, nociception, hyperthermia |
