Diabetic rats display increased
pain responses after injection of
formalin into the paw or thermal stimulation of the tail, suggesting the presence of
hyperalgesia. In this study, we investigated the efficacy of
URB597 (0.1, 0.3, and 0.5 mg/kg, i.p.), an inhibitor of
endocannabinoids metabolism, on 2 models of experimental
hyperalgesia in
streptozotocin (STZ)-induced diabetic rats. Animals were divided into control, URB597-treated control (0.1, 0.3, and 0.5 mg/kg), diabetic, and URB597-treated diabetic (0.1, 0.3, and 0.5 mg/kg) groups.
Formalin and tail-flick tests were performed 4 and 8 weeks after the onset of
hyperglycemia, respectively. Diabetes caused significant
hyperalgesia during these tests.
URB597 (0.3 and 0.5 mg/kg) reversed chemical and
thermal hyperalgesia in diabetic rats. Administration of
URB597 at a dose of 0.1 mg/kg did not alter
pain-related behaviors in control and diabetic groups compared with those of the respective control groups.
URB597 treatment did not affect
body weight or plasma
glucose level of treated animals compared with nontreated animals. This study shows that increasing
endocannabinoid neurotransmission with
URB597 displays efficacy in chemical and thermal models of diabetic
hyperalgesia. It also suggests that
URB597 is a promising tool for treatment of
painful diabetic neuropathy.