Middle ear procaine injection before surgical labyrinthectomy reduces nystagmus

: A middle ear injection of 2% procaine (0.1 ml) was given to guinea-pigs 15-30 min before a surgical unilateral labyrinthectomy (UL) and the effects on spontaneous ocular nystagmus (SN) were observed. The pre-UL injection of procaine significantly reduced SN frequency compared to vehicle-injected controls or to animals receiving a post-UL injection of procaine. This result supports the hypothesis that the decrease in resting activity observed in vestibular nucleus neurones following UL may be due, at least in part, to Ca2+ influx due to injury-related glutamate release from vestibular nerve terminals.