Heightened pain and delayed regeneration of galanin axons in diabetic mice.

Galanin peptide in primary sensory neurons may confer analgesia following injury. Its presence in regenerative axon sprouts where pain may be initiated has not been examined. We examined very early outgrowth of peptidergic axon sprouts after sciatic nerve crush in mice with experimental streptozotocin-induced diabetes. Diabetic mice had a retarded wave of outgrowing galanin axons, but those expressing calcitonin gene-related peptide grew normally. Diabetic mice also developed early, then persistent excessive autotomy behaviour, an index of pain behaviour in complete nerve lesions. Diabetes is associated with variations in the early outgrowth of peptide-containing axons. A relative delay in galanin axon outgrowth could contribute to heightened neuropathic pain in diabetes.