DIFFERENTIAL-EFFECTS OF FACIAL-NERVE TRANSECTION ON HEAT-SHOCK-PROTEIN-70 EXPRESSION IN THE DEVELOPING AND ADULT HAMSTER FACIAL NUCLEUS

In this study, the effects of axotomy on heat shock protein 70 (hsp70) protein levels were analyzed by immunoblotting with a hsp70 antibody that recognized constitutive and inducible forms of the protein. The r ight facial nerve of postnatal day 4 (neonate) or 100 (adult) hamsters was transected at its exit from the stylomastoid foramen, with the le ft nerve serving as internal control. Postoperative survival times wer e 2, 6, 12, and 24 h, with 3 animals per time point. Tissue punches co ntaining individual facial nuclear groups were collected and homogeniz ed. Approximately 10 mu g of total protein was loaded onto paired gels and electrophoretically separated. Immunoblots of one gel from each p air were prepared, with the other gel stained in 0.2% Coomassie blue a nd used for verification of equality of lane loading. The results indi cate that hsp70 protein levels increase in the adult, but decrease in the neonate, after axotomy. It is concluded that a stress response to cellular damage is an initial component of the classically described ' 'axon reaction'' and that hsp70 plays a role in mediating motoneuron s urvival after peripheral nerve transection.