Fig. 1

Excitatory connections from the deep cerebellar nuclei to the striatum. a Stereotaxic injection scheme in P18 mice. A glycoprotein-deficient retrograde rabies virus (RV-∆G-RFP) was injected into the dorsal striatum of one hemisphere and an adeno-associated virus (serotype 2; AAV2-GFP) expressing GFP under the control of the human synapsin promoter was injected into the contralateral deep cerebellar nuclei (DCN). b Primary AAV2-GFP infection sites in the DCN is confined to medial cerebellar nuclei (Med) and interposed cerebellar nuclei (IntA, IntP), but does not extend to the lateral nucleus (Lat). Two dorso-ventral (DV) planes are shown with the position relative to bregma indicated. Scale bar: 1 mm. c Scheme of horizontal section planes used for the analysis. d Example images of intralaminar thalamic nuclei (ILN) at two different dorsal–ventral planes. GFP-positive axons are concentrated in several ILN substructures, including the centrolateral thalamic nucleus (CL), parafascicular thalamic nucleus (PaF) as well as the ventrolateral thalamic nucleus (VL). Note that the fluorescence seen in the striatal area (ST) is tissue autofluorescence. Thalamic neurons retrogradely labeled from the dorsal striatum with RV-∆G-RFP are mostly observed in PaF and CL. The dashed rectangle marks the region enlarged in e. Scale bar: 500 µm. e Enlargement of ILN area. GFP-positive axons from DCN form varicosities onto RFP-positive neurons back-labeled from the dorsal striatum. Scale bars: 250 µm and 50 µm, respectively. f Some GFP-positive varicosities (arrow head) located on dendrites of RFP-positive cells are vGluT2-positive, indicating the presence of synaptic terminals. Scale bars: 10 µm. g Fluorescence intensity measurement demonstrating the alignment of a GFP- and vGluT2-positive varicosity apposed to a retrogradely marked RFP-expressing thalamic cell. Several consecutive optical sections from a z-stack are displayed. Scale bars: 10 µm. All experiments in this figure were replicated in three mice per condition. Anatomical annotations: APT anterior pretectal nucleus; fr fasciculus retroflexus; LDDM laterodorsal thalamic nucleus, dorsomed; LDVL laterodorsal thalamic nucleus, ventrolateral; LHb lateral habenular nucleus; MD mediodorsal thalamic nucleus; Po posterior thalamic nuclear group; PoMn posteromedian thalamic nucleus; pIRt- prosomere 1 reticular format; ST striatum; VL ventrolateral thalamic nucleus