POSTNATAL-DEVELOPMENT OF SPONTANEOUS TONIC ACTIVITY IN MOUSE MEDIAL VESTIBULAR NUCLEUS NEURONS

The timecourse of the appearance and maturation of intrinsic tonic act ivity in medial vestibular nucleus (MVN) neurones was examined using e xtracellular single unit recording techniques in slices of the dorsal brainstem prepared from balb/c mice at specific stages during the firs t postnatal month. In slices from animals at postnatal day 5 (P5), the intrinsic spontaneous discharge rate was low (< 5 impulses/s on avera ge). Over the period P10 to P30 this gradually increased to levels com parable to those of adult MVN cells in vitro. There was a rostro-cauda l gradient in the time-course of development of tonic activity, such t hat cells located rostrally within the MVN developed higher frequencie s of tonic discharge earlier than caudally located cells. The opening of the eyes around P14 was associated with a significant increase in t he mean discharge rate of caudally located, but not rostrally located, MVN cells.