LONG-TERM LOCAL CORTICOSTEROID APPLICATION DOES NOT INFLUENCE NERVE TRANSMISSION OR STRUCTURE

The long-term effects of a locally applied depot form of a corticoster oid on the electrical properties and structure of nerves were investig ated in an animal experimental model. The conduction in electrically s timulated A-fibres of the plantar nerve was monitored by a bipolar vol ley recording of the sciatic nerve whereas the conduction in C-fibres of the plantar nerve was measured through a C-fibre evoked segmental f lexion reflex in the anaesthetized rat. Droplets of either methylpredn isolone acetate or vehicle were placed under direct observation on the plantar nerve. Saline was used as a control on the contralateral side . One to two weeks after the application both the h-fibre volley of th e sciatic nerve and the C-fibre evoked reflex discharge of flexor moto neurons were recorded. No difference was found between the nerves trea ted with corticosteroid, constituent vehicle or saline. Light and elec tron microscopic analysis of the nerves showed no changes in the nerve fibres or in the intraneural connective tissue in either the corticos teroid treated or the control nerves. It is concluded that locally app lied corticosteroids in limited amounts have no long-term effects on t he electrical and structural properties of peripheral nerves.