Neuronal nitric oxide synthase decreased in the peripheral but not in the central nervous system of diabetic rats

We explored and compared the diabetic neuralgia induced in streptozotocin-treated rats, monitoring the expression of nitric oxide synthase in several areas of the central nervous system involved in nociceptive transmission, in the spinal ganglia and in the nodose ganglia. The threshold for heat noxious stimuli decreased in diabetic animals. The number of NADPH-d positive neurons decreased significantly in the spinal ganglia and in the nodose ganglia but not in the spinal cord, periaqueductal gray matter and cortex of diabetic animals. Insulin treatment prevented the decrease of the nociceptive threshold and the loss of NADPH-d positive neurons in the spinal and nodose ganglia. We confirmed the relationship between nociception, diabetes and NADPH-d neuronal expression in the spinal ganglia. We showed also that the nitric oxide is probably involved in the vagal diabetic neuropathy. These results suggest a different sensitivity to diabetes of central and peripheral nitroxidergic neurons.