The Effect of Streptozotocin-Induced Chronic Hyperglycemia on Respiratory Effects of Morphine in Rats

Neuropathic pain is a common complication of diabetes. Today opioid analgesics such as morphine, use for the management of neuropathic pain. Since the respiratory effects of morphine have not been studied in diabetes, the aim of this study was to investigate the effect of chronic hyperglycemia on the effects of morphine on respiration.

32 Male Wister rats were randomly allocated into control group (injection of citrate buffer as streptozotocin solvent), morphine group (injection of citrate buffer as STZ solvent and injection of morphine before respiratory recording) group, hyperglycemia group (STZ injection), and hyperglycemia-morphine group (STZ injection and morphine injection before respiratory recording). Hyperglycemia was induced by injecting streptozotocin (35 mg/kg, i.p.). Respiration was recorded by plethysmography after which respiratory volume, inter-breath interval, and respiratory rate were quantified using MATLAB.

Mean of respiratory rate (in the hyperglycemia was 83±3.9 and control was 101±4 (p<0.05)), coefficient of variation of respiratory rates (in the hyperglycemia was 0.615±0.1 and control was 1.05±0.07 (p<0.05)), mean of respiratory volume (in the hyperglycemia was 1.44±0.19 and was control 1.1±0.11 (p<0.05)), and mean of inter-breath interval (in the hyperglycemia was 1.28±0.01 and control was 0.93±0.03 (p<0.05)). coefficient of variation of respiratory volumes (in the hyperglycemia-morphine was 1.14±0.16 and was morphine was 1.68±0.1 (p<0.05)), mean of respiratory rate (in the hyperglycemia-morphine was 1.24±0.34 and morphine was 0.37±0.04 (p<0.05)), and mean of inter-breath interval (in the hyperglycemia-morphine was 1.09±0.07 and morphine was 0.74±0.05 (p<0.01)).

Our results show that chronic hyperglycemic changed breathing pattern and respiratory response to morphine.