Modified Irwin Test with Single Intravenous Administration of Caffeine in Mice

This study investigated the behavioral effects of intravenous caffeine administration in mice using a modified Irwin test. Thirty-two male ICR mice were divided into four groups and received intravenous doses of caffeine: 0 (control), 5, 10, or 20 mg/kg. Behavioral observations were conducted at 0, 0.25, 1.5, 6, and 24 h post administration. Notable traction, locomotion, and respiratory rate changes were observed at 10 and 20 mg/kg doses. Specifically, traction was altered at 0.25 and 1.5 h in the 10 mg/kg group, with more frequent alterations in the 20 mg/kg group. Increased locomotion (grade 6, characterized by frequent grooming and rapid movement) was observed in all the mice at 10 and 20 mg/kg doses between 0.25 and 1.5 h. Respiratory rate changes were observed only in the 20 mg/kg group during the same period. Our findings indicate that intravenous caffeine exposure significantly affects traction and locomotion, providing valuable insights for safe pharmacological testing of the central nervous system.