The Sciatic Nerve Preparation

In order to successfully investigate the properties of the sciatic nerve it is important to obtain as long a stretch of uninjured nerve as possible. The procedure to remove the nerve is relatively straightforward and is summarised below:

1. The frog is stunned and pithed, a procedure which destroys the brain and spinal cord.
2. A circular cut is made with scissors around the belly and the skin covering the lower half of the body removed (removing the "trousers").
3. The frog is laid dorsal surface uppermost and the urostyle removed by cutting through the muscle on both sides and finally cutting it away from the spinal column. At this point the sciatic nerve roots can be seen leaving the spinal cord on both sides. The nerve is ligatured close to where it leaves the spinal cord and cut anterior to the ligature. (Note: the cell bodies which lie in the spinal cord are thus removed.)
4. The nerve is carefully dissected free from surrounding tissue down to the knee joint. The path of the nerve through the thigh may be exposed by parting the muscles of the thigh using the thumbnails. Care must be taken not to touch the nerve with metal dissection instruments or to stretch the nerve unduly. Remember the functioning of the nerve depends on the integrity of the membrane. The nerve must be kept moist throughout with frog Ringer solution which closely resembles the extracellular fluid of the frog.
5. A ligature is tied around the nerve at the knee end and the preparation is placed in a small beaker of frog Ringer solution.