Intrastriatal targets of projection fibers from the central lateral nucleus of the rat thalamus

We examined light and electron microscopically intrastriatal targets of pro jection fibers from the central lateral thalamic nucleus (CL), which is a m ajor relay of cerebello-striatal projections. The study was done in the rat by combining the anterograde tract-tracing with immunohistochemistry for p arvalbumin (PV); an anterograde tracer (biotin dextran amine: BDA) was inje cted into the CL. In the striatum, 91% of BDA-labeled axon terminals made a symmetrical synapses on PV immunonegative dendritic spines (assumed to be t hose of striatal projection neurons); only 0.5% of BDA-labeled axon termina ls made synapses on PV immunopositive dendritic shafts. The remaining BDA-l abeled axon terminals were in synaptic contact with PV immunonegative dendr itic shafts. The results suggest that the cerebello-striatal projections th rough the CL predominantly access to striatal projection neurons, with only minor access to PV immunopositive (assumed to be GABAergic) interneurons i n the striatum. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.