Electrophysiological and horseradish peroxidase studies of precerebellar afferents to the nucleus interpositus anterior. I. Climbing fiber system.

The input to the nucleus interpositus anterior (NIA) of the cat from the inferior olive (IO) was studied by stimulating the IO while recording intracellularly from the NIA, and by the retrograde transport of horseradish peroxidase (HRP). Stimulation of the IO evoked monosynaptic EPSPs in NIA neurons. The cells labeled in the IO following electrophoretic and pressure injection of HRP into NIA were located in the rostral parts of the dorsal and medial accessory olive. Stimulation of the IO also polysynaptically evoked an IPSP and a late disinhibitory depolarization. Data were presented which indicated that these potentials were mediated by the Purkinje cells of the cerebellar cortex.