Immunocytochemical Localization of Glutamatergic Neurons in the Lateral Reticular Nucleus Projecting to Ansiform (Crus I and II) and Paramedian Cerebellar Lobules of the Rat

I examined the projection of glutamatergic neurons in the lateral reticular nucleus into ansiform (crus l and ll) and paramedian lobules in the rat cerebellum using immunocytochemical methods with antiserum against glutamate combined with WGA-HRP histochemistry. The projections of glutamatergic neurons from the lateral reticular nucleus to crus l were most extensive in number among the three injection cases and the majority of projections originated at the dorsal to dorsomedial region of the ipsilateral magnocellular nucleus. Glutamate-immunoreactive cells projecting to crus ll were less extensive in number than those projecting to crus l and were mainly localized at the dorsomedial portion of the ipsilateral magnocellular nucleus. Double-labelled neurons projecting to crus l or crux ll were also located at ipsilateral subtrigeminal as well as contralateral magnocellular nuclei. Glutamatergic neurons projecting to paramedian lobules were moderate in number and mainly located at the dorsal area of the ipsilateral magnocellular nucleus. A few double-labelled cells were also found at ipsilateral subtrigeminal or contralateral magnocellular nuclei. The present study suggests that glutamate-immunoreactive neurons at the dorsal to dorsomedial magnocellular division of the lateral reticular nucleus may participate in the excitatory control of target neuronal activities at ipsilateral, posterior hemispheric lobules of the rat cerebellum.