Evaluation of locomotor activity with open-field test for μ-opioid receptor knockout mice

Abstract

Gray matter volulme in periaqueductal gray (PAG) was increased in μ-opioid receptor knockout (MOP-KO) mice reported by voxel-based morphometry in magnetic resonace imaging. PAG is related to pain modulation with ascending autonomic and sensory input. We evaluated the locomotor activity with open-field test for MOP-KO mice. Tweleve wild-type and tweleve MOP-KO mice were used. Kinetic parameter was analyzed from ten minutes movie recorded by homemade video tarcking system. Mean velocity of wild-type and MOP-KO mice is 145.1±26.7mm/sec and 107.0±27.5 mm/sec, respectively, which was significantly defferent. Velocity fluctuation between wild-type and MOP-KO is almost same, according to the coefficient variation of velocity in wild-type and MOP-KO mice, which indicate 0.39±0.06 and 0.40±0.04, respectively. Moving velocity of MOP-KO mice might be reduced as a result of hyperalgesia.