Effects of dexamethasone on the electrical activity of spinal neurons in rats with the transected sciatic nerve

Effects of the glucocorticoid hormone dexamethasone on the reflex discharges in the lumbar ventral roots and background activity (BA) of single neurons in the dorsal laminae of spinal grey were studied in rats after transection of the sciatic nerve. Administration of the hormone during early post-traumatic period (up to seven days) evoked no significant changes in the amplitude of increased (due to the postdenervation hyperreflexia) monosynaptic discharges on the side of nerve transection. At the same time, the monosynaptic discharges grew by 150-170% on the intact side. During later post-transection periods (up to 35 days), when ventral root reflex discharges were suppressed, dexamethasone facilitated reflex transmission via the polysynaptic segmental pathways on both the operated and intact sides. Nonetheless, the monosynaptic component of reflex discharges on the injured side did not recover. Dexamethasone treatment resulted in an increase in the number of BA-generating interneurons within the superficial dorsal horn laminae, and in a decrease in the proportion of units generating bursting activity (possibly of pathological nature).