The systemic application of diazepam facilitates the reacquisition of a well-balanced vestibular function in a unilateral vestibular re-input model with intracochlear tetrodotoxin infusion using an osmotic pump.

Diazepam is a popular medicine used in the treatment of acute vertigo. In the past, many studies investigating the effect of diazepam in peripheral vestibular destruction have been reported. However, no previous study has yet investigated the effect of diazepam on a model with a transient and reversible vestibular function similar to recurrent vertigo as seen in Meniere's disease. We thus made a peripheral vestibular re-input model by the unilateral intracochlear administration of tetrodotoxin (TTX) using an osmotic pump and then examined the influence of diazepam on the vestibular system in this model. Hartley white guinea pigs were intracochlearly administered with TTX on the right side for 3 days by an osmotic pump. Animals were divided into three groups, TTX alone (control group (n = 7)), TTX and an intraperitoneal diazepam injection once a day for 3 days (diazepam group (n = 6)) and vehicle injection (vehicle group (n = 6)). A caloric response and vestibuloocular reflex (VOR) were observed at 7 and 14 days after completing 3 days of TTX administration. Seven days after vestibular re-input, a directional preponderance of the nystagmus (DP) to the TTX-treated side was observed in the control and vehicle groups on VOR examination. DP was not observed in the diazepam group on any examined day. The R/L time ratio of caloric response showed no statistical difference between three groups on any examined day. These results suggest that diazepam may thus be useful for patients in an acute stage of peripheral vestibular vertigo by decreasing their vertiginous symptoms.