The effects of steroids on vestibular compensation and vestibular nucleus neuronal activity in the guinea pig.

Recent studies have suggested that steroids such as dexamethasone and methylprednisolone might be useful in the treatment of vestibular disorders, irrespective of whether inflammatory processes are involved. The aim of this study was to investigate the effects of systemic administration of dexamethasone on vestibular compensation of spontaneous nystagmus (SN) in guinea pig, and the effects of dexamethasone and methylprednisolone on extracellularly recorded spontaneous activity of medial vestibular nucleus (MVN) neurons in brainstem slices in vitro. In the behavioral study, none of the 3 doses of dexamethasone (5, 10, or 40 mg/kg i.p., delivered at 0, 12, 24, and 36 h following a unilateral surgical labyrinthectomy (UL)) resulted in a significant change in the frequency or compensation of SN, relative to the vehicle control group. In the in vitro study, only a minority of MVN neurons showed any response to 1 microM dexamethasone (1 out of 9 neurons), or 10 nM (3 out of 13), or 0.1 microM methylprednisolone (3 out of 7). These results suggest, contrary to previous evidence, that dexamethasone may not accelerate compensation of SN following surgical UL and that dexamethasone and methylprednisolone may have a direct action only on a minority of MVN neurons.