Reduced Ia-afferent-mediated Hoffman reflex in streptozotocin-induced diabetic rats

In addition to reduced nerve conduction velocity, diabetic neuropathic pati ents often exhibit a reduction in the amplitude of the compound muscle acti on potential elicited by stimulation of the la-afferent-mediated reflex pat hway (Hoffman or H wave) that can contribute to diminished or absent tendon reflexes. In contrast to nerve conduction velocity deficits, changes in H- wave amplitudes have not been reproduced in diabetic animal models. Using e lectrophysiological techniques developed for repeated recordings in individ ual animals, we report H-wave deficits in streptozotocin (STZ)-treated insu lin-dependent diabetic rats. After 4 weeks of diabetes induced by STZ treat ment, a 47% reduction in the H-wave amplitude was demonstrated by recording compound muscle action potentials in foot muscles after stimulation of la afferents. Interestingly, we also demonstrate that the H-wave amplitude gra dually recovers to a 26% deficit after 12 weeks of experimental diabetes. T he recovery of the H wave in STZ-treated rats distinguishes this deficit me chanistically from other STZ-induced electrophysiological changes and may m odel a similar recovery of the H wave reported in diabetic patients. (C) 20 01 Academic Press.