NPUTS TO CEREBELLAR DENTATE NUCLEUS FROM THE PONTINE NUCLEUS IN THE CAT

Abstract

We have reported before that there are excitatory inputs to the cerebellar dentate nucleus (DN) from the cerebral cortex. This study was performed to examine whether the pontine nucleus (PN) and the nucleus reticularis tegmenti pontis (NRTP), which are among the precerebellar nuclei that relay inputs to the cerebellar cortex, also play a role as the relay nucleus of the excitatory input to the DN. In anesthetized cats, we stimulated the PN and the NRTP, and recorded intracellular potentials from DN neurons. Short-latency EPSPs were evoked from these nuclei and their latencies ranged from 1.1 to 3.6 msec, which are compatible with monosynaptic latencies. Systematic stimulation of the PN and the NRTP with weak stimulus intensities revealed that low-threshold foci for monosynaptic EPSPs in each cell were localized in the PN or the NRTP or both. We could not find monosynaptic inputs from the red nucleus and by recurrent collaterls of the dentate output neurons. Accordingly, the possibility was excluded that the monosynaptic EPSPs evoked from the PN and the NRTP were evoked by inadvertent current spread to the descending axons of DN neurons in the brain stem. The conditioning-testing stimuli of the cerebral peduncle and the PN or the NRTP yielded spatial facillitation. This result showed that the input from the cerebral cortex to the DN was relayed by way of the PN or the NRTP.