Paradoxical changes in spinal cord reflexes following the acute administration of acrylamide.

Acrylamide (ACR) produces a central-peripheral distal axonopathy when administered chronically. This is characterized functionally by decreases in the monosynaptic reflex (MSR) and dorsal root potential (DRP) and alterations in the characteristics of the dorsal root reflex (DRR). Acute administration of ACR inhibits the oxidative enzyme complex NADH-tetrazolium reductase and slows retrograde axoplasmic transport. This study was carried out to determine if the spinal cord reflexes are also affected following acute administration of ACR. Dose-response studies revealed a dose-dependent increase in both the MSR and DRR. A single injection of 50 mg/kg ACR caused an increase in both the MSR and DRR within 15 min and continued for over 3 h. These data are paradoxical since chronic administration of ACR results in decreased function. Two possible mechanisms are proposed. First, calcium ion regulation may be involved in both the acute and chronic effects of ACR on spinal cord reflexes. Second, a depolarization of the neurons is occurring just prior to cell injury or death.