Effect of intrathecal morphine on blood glucose, glucagon and tissue glycogen in rat: comparison with the effect of xanthan gum on blood glucose.

The effects of intrathecal (i.t.) morphine (25-100 micrograms) and of the intraperitoneal (i.p.) xanthan gum (30, 60 micrograms/kg) on blood glucose were studied in nonfasted rats. Morphine produced a time and dose-dependent hypoglycemia, whereas xanthan caused moderate decrease effect on blood glucose. Morphine and xanthan appears to be acting by different mechanisms, although the hypoglycemic effects of morphine appear to be due largely to an increased glucose uptake by skeletal muscle. Xanthan has a slow onset of hypoglycemic action which may allow homeostatic mechanisms to intervene. On the other hand, glucagon was increased significantly after i.t. morphine (50 micrograms) both at 30 and 60 min. The hyperglucagonaemic response after morphine may be due to a direct opioid effect on pancreas. The i.t. administration of morphine (50 micrograms) caused time-dependent decrease in liver and muscle glycogen levels in morphine-treated rats compared with saline-controlled rats. The data obtained point to the occurrence of active utilization of liver and muscle glycogen (glycogenolysis) in morphinized animals which is in concomitant with hypoglycemia and increased glucagon level recorded during the present work.