The effect of stress application on vestibular compensation

It is still unknown how stress, which is known to delay recovery from vestibular symptoms in patients with vertigo, influences recovery from vertigo. We therefore investigated the effect of stress on vestibular compensation following unilateral labyrinthectomy (UL) as a model of recovery from vertigo. In addition, we examined the effect of trilostane (4alpha, 5-epoxy-17beta-hydroxy-3-oxo-5alpha-androstane-2alpha-carbon itrile; TRIL), an inhibitor of the steroid biosynthesis enzyme delta5-3beta-hydroxysteroid dehydrogenase (3beta-HSD), on vestibular compensation under conditions of stress. After UL, Wistar rats were divided into five groups as follows and subjected to stress and/or drug application: UL only (native, n = 6); UL + stress (S, n = 6); UL + vehicle (V, n = 5); UL + stress + vehicle (S + V, n = 5); and UL + stress + TRIL (S + TRIL, n = 5). In the S group, the decrease in frequency of spontaneous nystagmus (SN) was significantly (p < 0.05) slower than, in the native group at 3, 12, 24, 30, 36 and 48 h. The decreases in frequency of SN in the V and S + V groups were similar to those in the native and S groups, respectively, suggesting that neither handling on injection nor administration of vehicle affected vestibular compensation. In the S + TRIL group, the frequency of SN was significantly (p < 0.05) less than that m the S + V group at 24 h after UL. At 30 h, the frequency of SN m the S + TRIL group was almost the same as that in the V group. These findings suggest that stress attenuates vestibular compensation and that changes in steroid concentrations account at least in part for this attenuation.