Changes in phrenic nerve compound muscle action potential in streptozotocin-induced diabetic rats

Purpose: To evaluate the phrenic nerve compound muscle action potential (CMAP) in rats after diabetes mellitus (DM) induction. Methods: Twenty DM animals(intravenous streptozotocin, 45 mg.kg- 1) and 25 controls underwent CMAP analysis before and 30, 60 and 90 days after DM induction. Results: Amplitude (mV) progressively declined in DM group after 30 (Mean difference (MD): -0.915, 95 % Confidence interval (CI) -1.580 to -0.250, p < 0.01), 60 (MD: -1.122, 95 % CI -1.664 to -0.581, p < 0.001) and 90 days (MD: -2.226, 95 % CI -3.059 to -1.393, p < 0.001); as well as the area (mV.ms) after 30 (MD: -3.19, 95 % CI -5.94 to -0.44, p < 0.05), 60 (MD: -3.94, 95 % CI -6.24 to -1.64, p < 0.001) and 90 days (MD: -8.64, 95 % CI -12.08 to -5.21, p < 0.001). Transient differences were observed in latency and duration at 60 days. Conclusions: The progressive changes in phrenic nerve CMAP observed during DM suggest a decrement in axonal function rather than substantial demyelination.