Morphometric analysis of the vagus nerve in non-diabetic and ketonuric diabetic Chinese hamsters.

Morphometric analysis of axons from the ventral division of the vagus nerve of ketonuric diabetic Chinese hamsters and age-sex matched non-diabetic controls was performed to determine the frequency distribution and numerical and volume density. Myelinated fibres of diabetics displayed a significant reduction in diameter (P less than 0.001) compared with controls, which was correlated inversely with progressive ketonuria (P less than 0.05). The reduced calibre of myelinated fibres was the result of thin myelin sheaths rather than a reduction in axon diameter. A marked decrease in numerical density (P less than 0.05) and volume density (P less than 0.005) was found in the myelinated fibres of diabetics compared with controls. Non-myelinated axons showed a significant shift to smaller diameter (P less than 0.001) in diabetics, which was correlated inversely with duration of ketonuria (P less than 0.05). Numerical density of non-myelinated axons was increased (P less than 0.01) in diabetic hamsters whereas volume density was comparable in diabetic and control animals. These data provide morphological evidence of impairment in the parasympathetic nervous system which may be a major factor underlying previously reported gastrointestinal and pancreatic islet dysfunction in the diabetic Chinese hamster.