The effects of continuous administration of diazepam on the recovery of lesion-induced nystagmus in unilaterally labyrinthectomised rats

BackgroundDiazepam, a gamma-aminobutyric acid type A receptor agonist, is classified as a vestibular suppressant and is effective in treating acute vertigo. However, its effects on vestibular compensation (VC) remain unclear.ObjectivesWe examined the effects of continuous administration of diazepam on the frequency of spontaneous nystagmus (SN) after unilateral labyrinthectomy (UL) as an index of the initial process of VC in rats.Materials and methodsDiazepam was continuously administered at doses of 3.5 and 7.0 mg/kg/day, intraperitoneally, via an osmotic minipump. The frequency of SN beating against the lesion side after UL was measured. Potassium chloride (KCl) solution (1 M) was injected intratympanically to induce SN beating to the injection side.ResultsContinuous administration of diazepam significantly and dose-dependently decreased the frequency of SN after UL, and also reduced the x intercept of the nonlinear regression curve of the decline in UL-induced SN with time in rats. However, the continuous administration of diazepam did not affect the frequency of intratympanic KCl-induced SN in the rats.ConclusionThese findings suggested that continuous administration of diazepam accelerates the initial process of VC; however, it does not suppress the nystagmus-driving mechanisms in rats.