Streptozotocin-induced diabetes decreases substance P levels in experimental arthritis in the rat knee.

Diabetic patients with sensory neuropathy are predisposed to disorders of the musculoskeletal system. It has been postulated that altered neurogenic inflammation, involving the neuropeptide substance P, may play a part in this phenomenon. We investigated the effect of streptozotocin-induced (STZ) diabetes on the development of an antigenic (mBSA) monoarthritis in the rat with particular reference to changes in substance P levels in dorsal root ganglia (DRG) and knee joint synovium. We found that STZ-induced diabetes of 24 weeks duration reduced the substance P content of L4/L5 DRG and knee joint synovial tissue. Induction of mBSA arthritis in diabetic rats resulted in diminished increases in synovial substance P and knee joint swelling compared to non-diabetic arthritic controls. The results show that chronic STZ diabetes reduces neurogenic inflammatory responses in the rat knee which may render the joint more susceptible to arthritic attack.