INDUCTION OF UROKINASE-TYPE PLASMINOGEN-ACTIVATOR IN RAT FACIAL NUCLEUS BY AXOTOMY OF THE FACIAL-NERVE

The response of plasminogen activator activity in the CNS to periphera l nerve axotomy was examined in vivo. After transection of the rat fac ial nerve, a transient increase in plasminogen activator activity was observed in the facial nucleus on the operated side with maximal activ ity 3-5 days after lesion. This activity was inhibited by the urokinas e-specific inhibitor amiloride but not by antibodies against tissue pl asminogen activator. The molecular mass of the induced form of plasmin ogen activator was estimated to be similar to 48 kDa. An in vitro assa y of plasminogen hydrolysis also demonstrated an increase in amiloride -sensitive plasminogen activator activity in facial nerve extracts fol lowing facial nerve axotomy. These data indicate that the plasminogen activator activity induced in the facial nucleus following axotomy of facial motoneurons is of the urokinase type. It is suggested that the urokinase-type plasminogen activator might play a role in the events a ccompanying injury and regeneration in the facial nucleus following mo toneuron lesion.