The vestibulo-ocular reflex arc in the newborn kitten. An electrophysiologic investigation.

Field potentials and postsynaptic potentials were recorded in the vestibular and abducens nuclei and neurons following vestibular nerve stimulation in anesthetized newborn kittens (within 72 h after birth). Stimulation of the ipsilateral vestibular nerve evoked an initial P wave and an N1 field potential in the vestibular nuclei. No N2 potential was evoked. Latencies of the peak of the P wave, the onset and the peak of the N1 potential were 0.99 +/- 0.16 ms, 1.66 +/- 0.18 ms, and 2.51 +/- 0.23 ms, respectively. Ipsilateral vestibular nerve stimulation evoked monosynaptic excitatory postsynaptic potentials (EPSPs) and polysynaptic inhibitory postsynaptic potentials (IPSPs) in vestibular nuclear neurons. Stimulation of the contralateral vestibular nerve evoked polysynaptic IPSPs in vestibular nuclear neurons. In abducens motoneurons, ipsilateral vestibular nerve stimulation evoked monosynaptic EPSPs and disynaptic IPSPs; contralateral vestibular nerve stimulation produced disynaptic EPSPs. We conclude that short circuit pathways of the vestibulo-vestibular and vestibulo-ocular reflex arc are present in the kitten already at birth.