INTRATHECAL ADMINISTRATION OF CLONIDINE SUPPRESSES AUTOTOMY, A BEHAVIORAL SIGN OF CHRONIC PAIN IN RATS AFTER SCIATIC-NERVE SECTION

The effect of chronic intrathecal (i.t.) administration of the alpha(2) adrenoceptor agonist clonidine on self-mutilation behavior (autotomy) after unilateral transection of the sciatic nerve was studied in rats. Rats injected with 10-mu-g clonidine twice daily for 21 days, starting 1 h before nerve section, autotomized significantly less than saline controls. However, in the few rats which received clonidine and autotomized, clonidine did not delay the onset of autotomy compared to saline controls. Termination of clonidine injection after 21 days resulted in increased autotomy within 1-4 days. No sedation or motor impairment was found after this dose of i.t. clonidine. It is suggested that clonidine may be useful in treating neuropathic pain in humans.