Age-related changes of enkephalin in rat spinal cord

Met-enkephalin immunoreactive material content was found to be decreased in the cervical and thoracic segments of the spinal cord from rats aged 25 months as comparedto young, 3-month -old rats. No age-related variations were detectable at the lumbar level. Bio_Gel P30 column chromatographyof thoracic segments extracts indicates that the composition of the immunoreactive material is similar in the two age-groups investigated. At the thoracic level opiate receptor binding was also measured. Opiate receptor number is increased in the thoracic segments of the spinal cord of older rats. These age-related changes in immunoreactive Met-enkephalin content and opiate receptor number at spinal levels may contribute to determine an altered pain sensitivity during aging.