Influence of FK506, Cyclosporin A, Testosterone and Nimodipine on Motoneuron Survival Following Axotomy

Injury to immature motoneurons results in extensive nerve cell death. Avulsion injury in adult animals has a similar effect. Rescuing injured neurons from degeneration and death is a prerequisite for succesful functional recovery. Here, we have explored the possible survival promoting effect of the immunosuppressant agents FK506 and cyclosporin A, the calcium channel blocker nimodipine as well testosterone on axotomized neonatal facial motoneurons. In addition, we examined the effect of cyclosporin A and Nimodipine, a calcium channel blocker, on survival of adult motoneurons following hypoglossal nerve avulsion. FK506 and cyclosporin A were administered intraperitoneally, testosterone intramuscularly and Nimodipine via the food. After the appropriate postoperative survival periods, the number of surviving facial or hypoglossal motoneurons respectively was calculated. FK506 and Cyclosporin A were found to enhance facial motoneuron survival following neonatal axotomy. Cyclosporin A and Nimodipine were found to promote motoneuron survival in adult rats after hypoglossal nerve avulsion. Nimodipine possibly also reduced motoneuron death in neonatal rats twenty-one days after facial nerve transsection, but failed to rescue motoneurons in neonatal rats during the first seven days after nerve injury. Treatment with testosterone was ineffective in preventing neonatal facial motoneurons from axotomy-induced death at seven days postaxotomy. The restults indicate that motoneuron degeneration can be counteracted to a large extent by immunosuppressant agents as well as by calcium channel blockers. Taken together with findings form previous studies, we conclude that motoneuron survival following axotomy can be promoted by a variety of endogenous and exogenous molecules acting on different cellular mechanisms.