Influence of water immersion stress on peripheral nerve recovery in the rat

An experimental study was performed to investigate the relationship between stress and peripheral nerve recovery. Male Wistar rats weighing 200-250 g were used. The sciatic nerve was crushed unilaterally with an aneurysm clip. Stress was applied by water immersion for 3 h, three times a week, from 1 week preoperatively, and continued for 6 or 8 weeks. The animals' walking tracks were measured every week to evaluate nerve function, and a sciatic functional index (SFI) was calculated. Specimens for histological examination were taken from the nerve at a site distal to the crush injury. By 3 weeks postoperatively, the SFI in the non-stress groups had recovered, but it remained at significantly lower levels in the stress groups (P < 0.01). Histological studies showed that the recovery of nerve fibers was retarded and regenerating axons were smaller in the stress groups. Peripheral nerve recovery after crush injury was suppressed by water-immersion stress.