The role of opioid receptors in diabetes and hyperglycemia-induced changes in pain threshold in the rat.
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.
Akunne
H C
HC
College of Pharmacy and Pharmaceutical Sciences, Florida A & M University, Tallahassee 32307.
Soliman
K F
KF
D000698:Analgesia; D000818:Animals; D002940:Circadian Rhythm; D003921:Diabetes Mellitus, Experimental / Q000503:physiopathology*; D006943:Hyperglycemia / Q000503:physiopathology*; D007328:Insulin / Q000494:pharmacology; D008297:Male; D009270:Naloxone / Q000494:pharmacology; D010146:Pain / Q000503:physiopathology*; D051381:Rats; D011919:Rats, Inbred Strains; D011957:Receptors, Opioid / Q000502:physiology*; D012684:Sensory Thresholds
D007328:Insulin; D011957:Receptors, Opioid; D009270:Naloxone