Intracellular analysis of antidromically and synaptically activated nucleus reticularis tegmenti pontis neurons

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.

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

Inputs to the nucleus interpositus anterior (NIA) of the cat from precerebellar nuclei which are thought to give rise to mossy fibers were studied using electrophysiological and anatomical techniques. Stimulation of one of these precerebellar nuclei, the lateral reticular nucleus (LRN) evoked monosynaptic EPSPs in NIA neurons. These EPSPs were followed by polysynaptic IPSPs and late depolarization mediated by the response of the cerebellar cortex. Similar responses were occasionally seen following stimulation of the brachium pontis (BP). When horseradish peroxidase was injected into the NIA, labeled cells were found in the magnocellular and parvicellular LRN, the external cuneate nucleus (ECN), the pontine nuclei and the perihypoglossal nuclei. There was no evidence for a direct projection of the nucleus reticularis pontis to the NIA. It was suggested that most of the tonic excitation of NIA neurons is provided by the LRN and ECN.