Glucocorticoid effects on spinal cord function

The effects of intensive glucocorticoid treatment on segmental spinal cord function in cats were examined. Adult cats were treated with triamcinolone (8 mg/kg) intramuscularly once daily for 7 days. On the first post-treatment day segmental spinal reflexes in the lumbar cord were studied. Under halothane anesthesia, a tracheotomy was performed and the spinal cord was transected at C1. Anesthesia was terminated and positive pressure ventilation with room air was begun. The lumbar cord was exposed and the popliteal fossa of one hindlimb was dissected to provide peripheral nerves for stimulation. All reflex responses were recorded at ventral root L7. Complete paralysis was maintained with gallamine. The 7-day intramuscular triamcinolone regimen was found to improve significantly the rate of monosynaptic recovery after single impulse transmission and the magnitude of monosynaptic post-tetanic potentiation. Single mono-synaptic impulse transmission was slightly increased while polysynaptic discharge was significantly enhanced. Presynaptic inhibition was greatly augmented, while postsynaptic and recurrent inhibitory mechanisms were not altered. It is concluded that these results mainly reflect a direct action of glucocorticoids on primary afferent terminals, increasing their responsiveness and evoked transmitter release. This finding may have relevance for beneficial effects of glucocorticoid therapy in pathologic and traumatic injuries in the central nervous system.