Thermal effects on horseradish peroxidase uptake in laser nerve transections

The authors previously reported that rat tibial nerves transected with CO2 or KTP/532 laser transmit less horseradish peroxidase (HRP) than those transected with a scalpel. This may be due to laser-specific effects or to thermal phenomena that are laser-independent. This study investigated potential thermal effects on the transmission of HRP through the tibial branch of the sciatic nerve in rats. Bilateral nerve transections were performed on 18 animals using a scalpel (control) or an electrocautery device, which simulated the thermal effects produced by lasers. HRP retrograde transport and deposition in the rat spinal cord were analyzed. Thirteen of 15 animals showed a higher number of HRP-labelled neurons on the scalpel side compared to the electrocautery side; a paired student's t test showed a significant difference (P = .028) in the numbers of HRP-stained cell bodies between the control group (x = 687.13 +/- 119.3) and the electrocautery group (x = 388.1 +/- 111.2). In conclusion, reduced HRP uptake in tibial nerves transected with lasers may be in part due to thermal effects produced by the lasers.