Autotomy following nerve injury: genetic factors in the development of chronic pain.

Several weeks following transection and ligation of the hind limb nerves in rats, the animals often attack their anaesthetic foot ("autotomy"). This behaviour is thought to reflect a sensory pathology analogous to anaesthesia dolorosa. We report here that the extent of autotomy varies greatly in genetically different populations of rats. Rats of one population, LC2, showed high autotomy levels; rats of another, LC1, showed very low autotomy levels. The main genetic difference between these two populations is the presence of inbred Lewis rat stock in the LC1 population. Pure Lewis strain rats proved to have very low autotomy levels. Thus, constitutional differences between different rat populations effect the extent of autotomy. These data may bear on the fact that after seemingly identical nerve injuries, some humans develop chronic pain syndromes and others do not. Our rat strains may provide a model for investigating the physiological basis of constitutional susceptibility to chronic pain.