Behavioral changes of Wistar rats with experimentally-induced painful diabetic neuropathy

With the purpose of studying data on spontaneous customary changes in diabetic rats, we induced diabetes in 28 Wistar rats with streptozotocin. The animals were observed for 27 weeks in an attempt to characterize spontaneous customary changes that could suggest signs of chronic pain. Morphine, as a central-acting potent analgesic and its specific antagonist naloxone, were used. Our results evidenced in the animals a clinical syndrome similar to human diabetes. Long-term customary analysis revealed a significant (p < 0.05) increase of scratching and resting/sleeping behaviors, but diminished motor, eating and grooming customs. Moreover, the thermal tests revealed hyperalgesia in 43% of the animals, what may corroborate the meaning of scratching as a sign of pain. Pharmacological tests with morphine showed a significant (p < 0.05) inhibition of scratch, with concomitant increase of motor and eating activities and diminished rest/sleep capacity. Naloxone antagonized the effects induced by morphine. Such results suggest that these animals exhibit evoked behavior of hyperalgesia and that scratch may possibly be a spontaneous manifestation of chronic pain also in Wistar rats with this experimental model of painful diabetic neuropathy.