Effects of vibration therapy on immobilization-induced hypersensitivity in rats

• Published in: Congress of the Japanese Physical Therapy Association Vol. 2014; p. 0105
• Main Authors: Hamaue Yohei, Sekino Yuki, Sakamoto Junya, Nakano Jiro, Okita Minoru
• Format: Journal Article
• Language: Japanese
• Published: JAPANESE PHYSICAL THERAPY ASSOCIATION 2015; 公益社団法人 日本理学療法士協会
• Subjects: hypersensitivity; immobilization; vibration
• ISSN: 0031-9406
• DOI: 10.1016/j.physio.2015.03.1960

【Purpose】Cast immobilization induces mechanical hypersensitivity, which disrupts rehabilitation. The purpose of this study was to investigate the preventive and therapeutic effects of vibration therapy on immobilization-induced hypersensitivity.【Methods】Thirty-five Wistar rats（8-weeks old；all male）were used. The right ankle joints of 30 rats were immobilized by plaster casts for 8 weeks, and 5 rats were used as controls. The immobilized rats were divided randomly into three groups：1）immobilization-only group（Im, n=10）, 2）vibration therapy group 1, with vibration therapy initiated just after the onset of immobilization（Im+Vib1, n=10）, and 3）vibration therapy group 2, with vibration therapy initiated 4 weeks after the onset of immobilization（Im+Vib2, n=10）. Vibration was applied to the hind paw for 15 min, once a day, for 5 days a week. The mechanical hypersensitivity and epidermal thickness of the hind paw skin were measured. To investigate central sensitization, the expression of the calcitonin gene-related peptide（CGRP）in the spinal cord and dorsal root ganglion（DRG）was analyzed.【Results】Immobilization-induced hypersensitivity was inhibited in the Im+Vib1 group but not in the Im+Vib2 group. Central sensitization, which was indicated by increased CGRP expression in the spinal cord and an increased DRG area with CGRP-positive neurons, was inhibited only in the Im+Vib1 group. Epidermal thickness was not affected by vibration stimulation.【Discussion】The reduction of CGRP over-expression in the spinal cord and DRG, which shows inhibition of the central sensitization, was observed in only the Im+Vib1 group. Our data suggested that the initiation of vibration therapy in the early phase of immobilization might inhibit the development of immobilization-induced hypersensitivity.