Histopathologic Changes in the Epidural Space of the Guinea Pig During Long-term Morphine Infusion

Abstract

A model for long-term epidural cannulation and toxicology testing for drugs applied in the epidural space of the Hartley guinea pig has been developed. The technique for cannulation is described. During long-term cannulation with a nylon catheter, extensive fibrous tissue reaction develops, which ultimately leads to some compression of the spinal cord. The inflammatory response is detectable at 2 days and is well organized by 14 days. One group of animals was injected daily with morphine sulfate. There were no histopathologic changes in the spinal cord and roots that could be attributed to the injection of morphine.