Intestinal motility responses to insulin and glucagon in streptozotocin diabetic rats

Abstract

Myoelectrical and mechanical activities were chronically recorded by use of nichrome electrodes and miniaturized strain-gage transducers sutured on the serosa of the antrum, the duodenum, and the jejunum, in a first experiment (n = 6 rats) the early (0–6 h) and late (> 4 days) effects of streptozotocin (65 mg/kg i.v.) was recorded. In addition, the effect of insulin (1–5 IU/kg) and glucagon (6–200 μg/kg) administered intravenously were studied separately each in groups of seven normal and streptozotocin-induced diabetic-fed and fasted rats. The results indicated that within the 30 min following streptozotocin administration there was a significant stimulation of the duodenal and jejunal motility lasting 46 ± 8 min. When diabetes was established as shown by the basal blood glucose level obtained in those rats (2.30 ± 0.84 g/L), a progressive decrease of the frequency of the migrating myoelectric complex was observed along with a disorganization of the regular spiking activity phases without disturbing the basal electrical rhythm. Comparing with the basal level, a significant increase in the gastrointestinal motility indexes (MI) appeared both in fasted (p < 0.01) and fed (p < 0.05) normal animals, 13.1 ± 1.6 min after an i.v. injection of 1 IU/kg insulin. Motor effects of glucagon were related to the dose. When used at 25 μg/kg a disorganization of the spiking activity was observed with a stimulation of the contractile activity in the jejunum. At higher dosages, i.e., 100 μg/kg, it induced an immediate and significant decrease of motility at any level tested and lasting up to 20 ± 7 min. The motility responses to both hormones were lower in diabetic than in normal rats.