Effects of ciliary neurotrophic factor on retrograde cell reaction after facial nerve crush in young adult rats

Abstract

Locally applied ciliary neurotrophic factor (CNTF) has a powerful effect on retrograde axonal reaction following facial nerve crush in neonatal rats. We examined whether it also exerts a strong effect on retrograde axonal reaction in young adult rats when administered subcutaneously. The dose was 1 mg/kg body weight, three times a week, similar to that used in a previous experiment in which CNTF was reported to have an effect. We studied changes in the morphology of the motor nerve cell bodies, in the number of perineuronal microglial cells and in the expression of five proteins. It appeared that CNTF prevented swelling of the facial motoneuron cell bodies but it did not influence the swelling of the nucleus nor the shift of the nucleus towards the periphery. In saline-treated rats, facial nerve crush resulted from day two to day six in a marked increase in the number of perineuronal glial cells. This increase was neither diminished nor augmented by CNTF. Following facial nerve crush, the immunoreactivity of the proteins C3bi, GFAP, B-50 and CGRP increased in the glial cells and motoneuron cell bodies, whilst the immunoreactivity of synaptophysin at the membrane of the motoneuron cell bodies decreased. CNTF had no obvious effect on these changes. It was concluded that in young adult rats under the present conditions, CNTF had only a small effect on a specific aspect of the retrograde cell reaction. The small effects might be explained by the minor availability of CNTF to the motoneuron cell bodies. The gain in body weight of rats treated with CNTF was less than that of saline-treated rats.