[Responsive property of afferent units in the caudal nerve of streptozotocin-diabetic rats].

In the present study, the responsive properties of afferent units in caudal nerve of streptozotocin (STZ) induced diabetic rats were investigated. It was found that some of the C and A delta units spontaneously discharged and their mechanical threshold was decreased significantly in diabetic rats. The response of the C units of diabetic and control rats to a 1 min sustained mechanical stimulus of threshold strength was similar, whereas, discharge frequencies during sustained suprathreshold mechanical stimulus were significantly greater in the C units of diabetic rats. After removal of threshold or suprathreshold mechanical stimulus, after discharges were also greater in C units of diabetic rats. Conduction velocity of C units, A delta units and A beta mechanical receptive units were also decreased in diabetic rats. However, there was no significant difference in the subunits of all kinds of receptive units between diabetic and control rats. The present data suggested that the C and A delta units with lowered mechanical threshold contribute to the decrease of the behavioral nociceptive threshold of diabetic rats and abnormal discharge of the C and A delta units may be a peripheral factor in hypersensitivity to painful stimuli and paresthesia of diabetic rats.