Effect of streptozotocin-induced diabetes on the autonomic ganglia of albino rats

Abstract

Objectives : One of the common clinical observations regarding long-standing hyperglycemia is autonomic neuropathy, probably due to its unfavorable destructive effects on the neurons of the autonomic ganglia. Accordingly, the current study was aimed to analyze the effect of experimental hyperglycemia on parasympathetic pterygopalatine ganglion (PtG) and sympathetic coeliac ganglion (ClG) of albino rats. Methods: Thirty-six albino rats were divided into six groups (n=6, each) and were designated as control, two weeks, one month, two months, four months and six months groups. Diabetes was induced with a single dose of streptozotocin (STZ, 60 mg/kg, i.p.). Body weight and blood sugar were monitored at biweekly intervals. At the end of each experimental period, animals were euthanized by deep ether anesthesia and blood samples were collected by direct puncture of heart for biochemical analysis. Animals were perfused with Karnovsky fixative. After 48 hours, tissue samples were collected and processed for light microscopy. Results : Biochemical analysis of serum revealed increased serum creatinine and reduced serum total protein. Histopathology and histomorphometry of ganglia revealed that the progressively increasing duration of hyperglycemia was associated with decreased proportion of small-sized neurons, increased proportion of large-sized neurons, dark and dead neurons, and thickening of capsular and endoneurial collagen. Conclusion: The association of the long-standing hyperglycemia with increased neuronal death, altered proportion of neurons and deposition of collagen fibers in autonomic ganglia appear to be important contributing factors likely to be responsible for diabetic autonomic neuropathy.