The nucleus reticularis tegmenti pontis and the adjacent rostral paramedian reticular formation: differential projections to the cerebellum and the caudal brain stem

Summary The projection of the nucleus reticularis tegmenti pontis and the adjacent tegmental area, to the caudal brain stem and the cerebellum were investigated by means of anterograde transport of tritiated leucine. The nucleus reticularis tegmenti pontis was found to be exclusively connected with the cerebellum. Mossy fiber terminals were absent only from lobule X and most abundant in lobule VII and the hemispheres with a slight contralateral predominance. The paramedian pontine reticular formation projects with bilateral symmetry to the cerebellar lobules VI, VII and the crura I and II, and heavily to the medial aspect of predominantly the ipsilateral reticular formation in the lower brain stem including specific targets as the nucleus reticularis paramedianus, the nucleus prepositus hypoglossi, the nucleus intercalatus, the nucleus of Roller, the nucleus supragenualis and the dorsal cap of the inferior olive. The nucleus vestibularis medialis receives a very weak projection. The connections are discussed in the light of their possible involvement in pathways for the execution of voluntary and reflex eye movements.Abbreviations bp brachium pontis - CBL cerebellum - cr I, II crus I, II - ct corpus trapezoides - dc dorsal cap of Kooy - dl dorsal lamina of the principal olive - FL flocculus - flm fasciculus longitudinalis medialis - gVII genu of the facial nerve - H VI hemisphere of lobule VI - IO inferior olivary nucleus - ll lemniscus lateralis - ml lemniscus medialis - NCS nucleus centralis superior - NIC nucleus intercalatus - NP nuclei pontis - NPH nucleus prepositus hypoglossi - NRaP nucleus raphe pontis - NRGc nucleus reticularis gigantocellularis - NRL nucleus reticularis lateralis - NRo nucleus of Roller - NRP nucleus reticularis paramedianus - NRPoC nucleus reticularis pontis caudalis - NRPoO nucleus reticularis pontis oralis - NRTP nucleus reticularis tegmenti pontis - NSG nucleus supragenualis - NVM nucleus vestibularis medialis - N VI nucleus abducens - n XII nervus hypoglossus - ped pedunculus cerebri - PFLD dorsal paraflocculus - PFLV ventral paraflocculus - PMD paramedian lobule - PPRF pontine paramedian reticular formation - vl ventral lamina of the principal olive - vlo ventrolateral outgrowth - X nucleus dorsalis vagi - XII nucleus hypoglossus - I-X lobules I to X