When the axon of a neurone is transacted, the neurone is said to be axotomized. This occurs when the nerve trunk is cut, crushed, ligated or frozen. The stump of the axon becomes swollen with accumulated organelles originally destined for the nerve terminals. The soma responds within ~ 6 hours, by changing the synthesis of proteins from transmitter synthesizing enzymes, to those associated with regeneration of axonal membrane and other structural components. If regeneration is prevented by scar formation or another impediment, a neuroma forms. Axotomy of the sciatic nerve, particularly in rats or mice, is frequently used as an animal model for nerve injury and neuropathic pain.