Z.G. is supported by NINDS R01NS100801.

Animal experiments were approved by UCSF Institutional Animal Care and Use Committee and were conducted in accordance with the NIH Guide for the Care and Use of Laboratory animals. Adult C57BL/6 mice weighing 20-30 g was used in this study. The von Frey assessment was performed between 1:00 pm and 3:00 pm.
1. Anesthesia and mouse preparation
<ol>
	<li>Place a mouse in a plastic chamber filled with 2% isoflurane in O2 at a flow rate of 1.0 L/min until it is fully a...

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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, ...

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&#39;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&#39;s lab, in which the common peroneal and the sural nerves were injured, leaving the tibial nerve intact7,8. The initial Woolf&#39;s model is defined as SNIs here because the sural nerve is left intact, and Basbaum&#39;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.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>6-0 suture</td>
			<td>Henry Schein</td>
			<td>9007482</td>
			<td>Nerve ligation and close the muscular layer</td>
		</tr>
		<tr>
			<td>Iris Scissors</td>
			<td>Integra Miltex</td>
			<td>12460598</td>
			<td>Cut muscle and fascia</td>
		</tr>
		<tr>
			<td>Mayo dissecting scissors</td>
			<td>Fisherbrand</td>
			<td>895120</td>
			<td>Cut skin incision</td>
		</tr>
		<tr>
			<td>Micro forcep</td>
			<td>Fisherbrand</td>
			<td>16100110</td>
			<td>Blunt dissection biceps femoris muscle</td>
		</tr>
		<tr>
			<td>Micro Scissors</td>
			<td>Excelta</td>
			<td>17467496</td>
			<td>Cut nerve</td>
		</tr>
		<tr>
			<td>Microdissection Forceps</td>
			<td>Fisherbrand</td>
			<td>16100123</td>
			<td>Separate the common peroneal and the sural nerves from the neighboring tissues</td>
		</tr>
		<tr>
			<td>Needle Holder</td>
			<td>Fisherbrand</td>
			<td>8966</td>
			<td>Hold 6-0 needle</td>
		</tr>
		<tr>
			<td>Prism software</td>
			<td>Graph Pad</td>
			<td>version 8.0</td>
			<td>Statistical analysis software</td>
		</tr>
		<tr>
			<td>Wound clips</td>
			<td>Roboz Surgical</td>
			<td>NC1878744</td>
			<td>Close skin incision</td>
		</tr>
	</tbody>
</table>

modified spared nerve injury surgery model of neuropathic pain in mice

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.

The comparison of procedure time between modified and traditional methods. 
The procedure time from the beginning of cutting the skin to the end of closing skin was recorded in 5 mice with the modified approach and 5 mice with the traditional approach, respectively. A minimal number of animals was used to obtain results with statistical significance. Compared with the control of the traditional approach7,14 to perform SNIt, the modified appr...

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Modified Spared Nerve Injury Surgery Model of Neuropathic Pain in Mice

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 ...

To cut and ligate a common peroneal and sural nerves with intact tibial nerve, defined as SNIt, has much less motor deficit with a shorter learning curve. The 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. To begin, place the mouse in a right lateral position.Keep the left leg up with knee flexion, and secure it with adhesive tape. Remove the hair around the thigh and knee area with an electric shaver and hair removal cream. After placing the mouse on a new sterile surgery towel, disinfect the skin with 2%chlorhexidine and 70%alcohol.Secure it with adhesive tape. Cut a one centimeter incision starting at one third of the horizontal line, crossing the knee with an approximately 30 degree angle from the vertical line with a scalpel. Two white lines can be visualized under the biceps femoris muscle after separating skin incision with the medial cephalad thick line above the femur and lateral caudal thin line above sciatic nerve.Blunt dissect the biceps femoris muscle along the caudal white line using curved micro forceps and micro scissors to expose the sciatic nerve. Differentiate the three branches from the sciatic nerve at the superior edge of the gastrocnemius muscle. The tibial nerve has the biggest diameter passing under the gastrocnemius muscle, whereas the sural nerves are lateral and smallest in diameter.The common peroneal nerve runs above the gastrocnemius muscle. Depending on how the biceps femoris muscle is dissected and opened, visualize the common peroneal nerve as lateral or medial to the tibial nerve. Then separate the common peroneal and the sural nerves from the neighboring tissues using curved micro forceps.Ligate the common peroneal and sural nerves together with a 6/0 suture. Both nerves run above the gastrocnemius muscle, but the tibial nerve passes under the gastrocnemius muscle. Observe the limb for contraction following the tight ligature.Cut nerve at a distal part within two to four millimeters of the ligation with a pair of micro scissors. Ensure that the tibial nerve remains untouched during the whole procedure. Close the muscular layer with a 6/0 silk suture and close the skin incision with wound clips.The results show that the modified approach took almost half the amount of procedure time to perform SNlt compared with the control of the traditional approach. No difference in Von Frey assessment was observed in the two groups at baseline. The traditional method and the modified method induced similar mechanical hypersensitivity on the ipsilateral side from postoperative day one to postoperative day 14.The percentage response between traditional and modified methods showed similar mechanical hypersensitivity on the ipsilateral side from baseline. Easy and rapid exposure of the sciatic nerve, accurate identification of the common peroneal, tibial, and sural nerves, cutting and ligation of the common peroneal and sural nerves are the three critical steps in this protocol. The method was successfully developed to mimic peripheral nerve injury cardio symptoms and randomized to study the molecular and cellular mechanism of neuropathic pain.

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JoVE Journal

Neuroscience

3.7K vistas.  Capital Medical University. Cortar y ligar un nervio peroneo y sural común con el nervio tibial intacto, definido como SNIt, tiene mucho menos déficit motor con una curva de aprendizaje más corta. El procedimiento de cirugía SNIt modificado en ratones se desarrolló para ligar los nervios peroneo y sural comunes junto con una sola ligadura de nervios y un corte de nervio, lo que resulta en un tiempo de procedimiento más corto. Para empezar, coloque el ratón en una posición latera...