Reciprocal connections between the nucleus interpositus of the cerebellum and precerebellar nuclei.

Reciprocal excitatory connections which give rise to reverberatory activity were investigated by intracellular recording and retrograde horseradish peroxidase (HRP) transport. Neurons in the interpositus nucleus (IP) were activated antidromically from the nucleus reticularis tegmenti pontis (NRTP) and paramedian reticular nucleus (PMRN). Stimulation of these nuclei and lateral reticular nucleus (LRN) elicited monsynaptic EPSPs in IP neurons. PMRN neurons could be activated antidromically as well as orthodromically from IP. HRP-positive neurons were found in NRTP, PMRN and LRN following injection of HRP into IP. Neuronal connections of IP-NRTP-IP, IP-PMRN-IP and IP-RN-LRN-IP were suggested as possible components of reverberating circuits.