Reinnervation of muscles after transection of the sciatic nerve in adult rats

Abstract

Functional recovery after transection of the sciatic nerve in adult rats is poor, probably because of abnormalities in reinnervation. Denervation and reinnervation patterns were studied morphologically in the lateral gastrocnemius (LGC), tibialis anterior (TA), and soleus (SOL) muscles for 21 weeks after nerve transection (motor endplates by acetylcholinesterase staining; nerves by silver impregnation). Motor endplates in the TA showed improving morphology with age, and, at 21 weeks, three-quarters of these were normal. Poorest recovery was observed in the SOL, as, at 21 weeks, only one-third of the motor endplates had a normal morphology. Polyneuronal innervation initially was more pronounced in the SOL, but, at 21 weeks, 10% of the motor endplates in all three muscles were still polyneuronally innervated. Our results indicate important differences in the reinnervation of these three hindleg muscles, and, even at 5 months, abnormalities were still present. These factors may in part explain the abnormal locomotion in rats as well as the limited recovery of function observed clinically in humans after nerve transection.

Regeneration of Reinnervated Rat Soleus Muscle Is Accompanied by Fiber Transition Toward a Faster Phenotype

“…However, the repaired nerve started to regenerate, reinnervating the hindlimb muscles z7 weeks after the operation (Ijkema-Paassen et al 2002). In accordance with other morphological, motor endplate, and functional studies of sciatic nerve recovery (Hare et al 1992;Sterne et al 1997;IjkemaPaassen et al 2001IjkemaPaassen et al ,2002, we found that by 3-4 months after microsurgery, the weight and morphology of reinnervated soleus muscles reached a near-optimal status and improved only slightly afterwards (Pinte´r et al 2003).…”

“…To gain information about the innervation state of the affected muscles, we performed AChE staining of motor endplates as well (Figures 2D-2F; Pinte´r et al 2003). In reinnervated muscles, we confirmed the findings of others (Ijkema-Paassen et al 2002) who found highly variable motor endplates, several of which were characterized by abnormal (fragmented or granular) morphology ( Figure 2E, arrowheads; see also inset). In reinnervated-regenerated muscles (i.e., on day 28 of regeneration), we observed motor endplates with similar morphological abnormalities coupled several times to smaller fibers (Figure 2F, arrowheads;Pinte´r et al 2003).…”

Effect of Sciatic Nerve Transection on acetylcholinesterase activity in spinal cord and skeletal muscles of the bullfrog Lithobates catesbeianus

“…Interestingly, the effect of SNT on AChE activity in bullfrog skeletal muscles was similar to the one described for mammals (Glisović et al, 2010;Ijkema-Paassen et al, 2002;Guth et al, 1964). However, while SNT induced a rapid initial decrease in AChE activity in rat skeletal muscles (Guth et al, 1964), such reduction occurred later and more slowly in bullfrog tissues.…”

“…In mammals and birds, SNT cause temporary decrease in AChE activity in skeletal muscles and nervous tissue (Ijkema-Paassen et al, 2002;Wan et al, 1997). In frog Rana pipiens, it has been demonstrated that spinal-cord AChE activity did not significantly change in the first days following ventral root transection (Sinicropi et al, 1982), another model to study neuropathic pain (Jaggi et al, 2011;Klusáková and Dubový, 2009).…”

“…Thus, our study assessed the effect of SNT on AChE activity in lumbosacral spinal cord of Lithobates catesbeianus. We also assessed the effects of SNT on AChE activity in bullfrog tibial posticus and gastrocnemius muscles because SNT has been shown to induce time scale differences of motor endplate maturation in skeletal muscles of rats (Ijkema-Paassen et al, 2002). Tibial posticus was chosen because it is a postural muscle in frogs (Crockett and Peters, 2008), and gastrocnemius is a typical skeletal muscle that is frequently used to study the motor system.…”