Thyrotropin-Releasing Hormone Analog Taltirelin Inhibits Acute and Chronic Itch in Mice

Itch is an unpleasant sensation that induces a desire to scratch. Chronic itch is accompanied by inflammatory skin diseases and causes repetitive scratching leading to tissue damage. The thyrotropin-releasing hormone analog taltirelin exerts analgesic effects on acute and chronic pain by activating the descending inhibitory systems. However, little is known regarding its effects on acute and chronic itch. In this study, we examined the effects of taltirelin on acute and chronic itch. Subcutaneous injection of chloroquine increased the number of scratching bouts in 30 min, whereas intraperitoneal injection of taltirelin reduced these episodes in a dose-dependent manner. In addition, chronic itch induced by diphenylcyclopropenone treatment was alleviated by taltirelin injection. These findings indicate that taltirelin alleviates acute and chronic itch in mice, and can be a potent therapeutic antipruritic drug.