The modified surgery is a simplified method for mouse or rat spared nerve injury model that requires only one ligation and one cut to injure both common peroneal and sural nerves.
Spared nerve injury (SNI) is an animal model that mimics the cardinal symptoms of peripheral nerve injury for studying the molecular and cellular mechanism of neuropathic pain in mice and rats. Currently, there are two types of SNI model, one to cut and ligate the common peroneal and the tibial nerves with intact sural nerve, which is defined as SNIs in this study, and another to cut and ligate the common peroneal and the sural nerves with intact tibial nerve, which is defined as SNIt in this study. Because the sural nerve is purely sensory whereas the tibial nerve contains both motor and sensory fibers, the SNIt model has much less motor deficit than the SNIs model. In the traditional SNIt mouse model, the common peroneal and the sural nerves are cut and ligated separately. Here a modified SNIt surgery method is described to damage both common peroneal and sural nerves with only one ligation and one cut with a shorter procedure time, which is easier to perform and reduces the potential risk of stretching the sciatic or tibial nerves, and produces similar mechanical hypersensitivity as the traditional SNIt model.
Nerve injury-induced neuropathic pain following surgery or trauma has a significant economic burden that impairs quality of life. A host of nerve injury models, including spinal nerve ligation (SNL)1, chronic constriction injury (CCI)2 to the sciatic nerve, partial sciatic nerve ligation (pSNL)3, sciatic nerve transaction (SNT)4 and spared nerve injury (SNI)5,6,7,8, were successfully developed to mimic the cardinal symptoms of peripheral nerve injury in rats and mice for studying the molecular and cellular mechanism of neuropathic pain6,7,8,9,10. However, each surgical model has its benefits and limitations, therefore particular attention should be given to exploring and developing the surgery models10.
The rodent SNI model produces long-term hypersensitivity to mechanical stimulation. However, it is somewhat confusing because there are two different SNI models. The initial SNI model was developed in Woolf's lab, in which the common peroneal and the tibial nerves were injured, leaving the sural nerve intact5,6. The second SNI model was developed in Basbaum's lab, in which the common peroneal and the sural nerves were injured, leaving the tibial nerve intact7,8. The initial Woolf's model is defined as SNIs here because the sural nerve is left intact, and Basbaum's model is defined as SNIt here because the tibial nerve is left intact. Because the sural nerve is purely sensory whereas the tibial nerve contains both motor and sensory fibers, the SNIt model has much less motor deficit than the SNIs model. However, unlike the SNIs model, mice in the SNIt model do not develop thermal hypersensitivity, but mechanical hypersensitivity develops in both models. Although the SNIt model is a relatively easy procedure, it requires the ligation of the sural and common peroneal nerves separately with the potential risk of stretching the sciatic or tibial nerves6,7,8,9.
The common peroneal, tibial, and sural nerves are three branches of the sciatic nerve and can be clearly identified at the superior edge of the gastrocnemius muscle (Figure 1): the tibial nerve goes under the gastrocnemius muscle, and the common peroneal (cephalad side) and sural nerve (caudal side) are above the gastrocnemius muscle11. Based on its anatomical features, a modified mouse SNIt surgery procedure was developed to ligate the common peroneal and sural nerves together with only one nerve-ligation and one nerve-cutting, which results in shortened procedure-time.
Compared to the traditional mouse SNIt method that ligates the common peroneal nerve and the sural nerve separately6,7,8,9, the modified SNIt model has three advantages: (1) it has less risk of contracting or stretching sciatic or tibial nerves; (2) there is no need to remove the distal nerve stumps after nerve-cutting because by ligating the common peroneal nerve and the sural nerve together, …
The authors have nothing to disclose.
Z.G. is supported by NINDS R01NS100801.
6-0 suture | Henry Schein | 9007482 | Nerve ligation and close the muscular layer |
Iris Scissors | Integra Miltex | 12460598 | Cut muscle and fascia |
Mayo dissecting scissors | Fisherbrand | 895120 | Cut skin incision |
Micro forcep | Fisherbrand | 16100110 | Blunt dissection biceps femoris muscle |
Micro Scissors | Excelta | 17467496 | Cut nerve |
Microdissection Forceps | Fisherbrand | 16100123 | Separate the common peroneal and the sural nerves from the neighboring tissues |
Needle Holder | Fisherbrand | 8966 | Hold 6-0 needle |
Prism software | Graph Pad | version 8.0 | Statistical analysis software |
Wound clips | Roboz Surgical | NC1878744 | Close skin incision |
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