The role of opioid receptors in diabetes and hyperglycemia-induced changes in pain threshold in the rat

Abstract

The role of opioid receptors in diabetes and hyperglycemia-induced analgesia was studied in male Sprague-Dawley rats. Animals maintained under controlled environmental conditions were used in all studies. Pain latency was determined by the hot plate test (55 degrees C) and analgesy-meter force method. The results of these studies indicate that streptozotocin-induced diabetic animals have a significantly higher pain threshold (P less than 0.01) than the control groups. The pain threshold was found to be diurnally controlled with a peak at the beginning of the light phase (1000 hours) and a trough at the end of the dark phase (0800 hours). Diabetes-induced analgesia was found to be reversed by both acute or chronic insulin administration. In another study, glucose-induced hyperglycemic rats were found to have a significantly higher pain threshold (P less than 0.01) than control animals, with a peak occurring at the beginning of the dark phase (2000 hours), and a trough at the beginning of the light phase (0800 hours). The administration of the opioid antagonist naloxone (2 mg/kg) reversed the hyperglycemia and diabetic-induced analgesia. The results of these studies might indicate that analgesia found in diabetic or hyperglycemic animals may be related to the endogenous opioid system.

The hyperalgesic effect of naloxone is attenuated in streptozotocin-diabetic mice

“…For example, genetically diabetic mice are shown to have increased reaction latencies to tail pinch and radiant heat (Levine et al 1982b). Similarly, in the hot plate test, streptozotocin-induced diabetic animals and dextrose-induced hyperglycemic animals were reported to show an elevation in pain threshold (Chu et al 1986;Akunne and Soliman 1987). In contrast, decreases in paw-lick and jump latencies have been reported in streptozotocin-treated rats (Forman et al 1986).…”

Diabetic Neuropathy in Spontaneously Diabetic Torii Rat

“…Duration of hyperglycemia, the severity of diabetic state, sex or species may affect progression to diabetic hyper-or hypoalgesia. While thermal hypoalgesia is reported in diabetic animals using tail-flick test or hot plate test [23][24][25], others have found hyperalgesia [26][27][28]. At 32 weeks of age, marked thermal hypoalgesia was observed in SDT rats by tail-flick test [17].…”

Assessment of Anti-Diabetic Activity of Syzygium jambolanum Using In vitro Model

“…There are many studies of hyper and hypoalgesia in STZ-induced diabetic animal models. While thermal hypo-algesia is reported in diabetic rats using the tail-flick test or the hot-plate test [2,3,6,10,19,20] , others have found hyperalgesia in diabetic animals [13,31,37,38] . In the present study, alloxan-induced diabetic rats showed hyperalgesia in the formalin test and showed thermal hypoalgesia.…”