Development of short latency vestibular evoked potentials in the neonatal rat

The development of short latency vestibular evoked potentials (VsEPs) was i nvestigated in the neonatal rat. Using the appropriate stimulus (linear or angular acceleration impulses) and head orientation, responses elicited in various vestibular end-organs (utricle: x-VsEP; saccule: z-VsEP; lateral se mi-circular canal: a-VsEP) were measured in rat pups at various ages betwee n post-natal days (PND) 5 and 30, and compared to those recorded from adult animals. It was found that the VsEPs initially appeared on PND 6 (x-VsEPs and z-VsEPs) or 7 (a-VsEPs), and that by PND 8 the three responses could be recorded in all animals. The first wave of the responses, generated in the primary sensory nerve and reflecting end-organ activity, reached adult lat encies and amplitudes by PND 10, showing rapid maturity of the responses. A uditory responses, on the other hand, develop at a later stage (from PND 11 ). The possible mechanisms involved in this differential maturation between vestibular and auditory activity are discussed. (C) 1999 Elsevier Science B.V. All rights reserved.