Effects of diabetes on cholinergic transmission in two rat gut preparations

The gut may be a site of early diabetic neuropathy in humans and rats. The latter may provide appropriate models of these conditions. Therefore, cholinergic function was examined in two gut smooth muscle preparations from control, 30-day, and 6-month streptozotocin-diabetic and similarly diabetic rats that had received continuous treatment with an aldose reductase inhibitor, ponalrestat. Responses of terminal ileum longitudinal muscle to transmural nerve stimulation were depressed in preparations from untreated 30-day diabetic animals. Responses to exogenous acetylcholine were also depressed, by at least the same extent, in preparations from both 30-day and 6-month diabetic groups. Ponalrestat treatment prevented both changes in the 30-day study but did not prevent a depression of responses to acetylcholine in the 6-month study. Neither diabetes nor ponalrestat affected responses of esophageal muscularis mucosa to electrical stimulation or to exogenous acetylcholine. These observations suggest a change in the smooth muscle and/or noncholinergic innervation rather than in the cholinergic nerves of the ileal preparation. Cholinergic function in the ileum did not, therefore, seem to be an appropriate model of diabetic neuropathy.