Primary afferent terminal function following acrylamide: alterations in the dorsal root potential and reflex

The dorsal root potential (DRP) and the dorsal root reflex (DRR) were studied in acrylamide (ACR)-induced axonopathy to determine the nature and extent of primary afferent terminal (PAT) dysfunction. Cats were administered 30 mg/kg/day ACR for either 5 (ACR 5D) or 10 (ACR 10D) days. The day after the last injection, the spinal cord as isolated in situ and the DRP and DRR were elicited. It was found that only 21% of the ACR 10D animals exhibited a DRP. Furthermore, in that 21%, the DRP appeared to degrade over distance differently from the control group. There was no change in the DRP evoked in the ACR 5D group. ACR affected the DRR when evoked from the cutaneous sural nerve (SU) to a greater extent than when evoked from the medial gastrocnemius (MG) nerve. A SU-evoked DRR could not be elicited in any of the animals in the ACR 10D group and in only 20% of the ACR 5D group. There was no difference in the ability to elicit a MG-evoked DDR in either ACR-treated group when compared to control. However, the maximum-evoked area under the DRR elicited from the MG nerve was significantly smaller in the ACR-treated groups than in control. These data show that ACR does indeed impair PAT function. ACR preferentially affects the PAT processing of the SU when compared to the MG nerve, which may indicate that the selective vulnerability of the largest diameter fibers to ACR is not necessarily true.