THALAMIC RETICULAR INPUT TO THE RAT VISUAL THALAMUS - A SINGLE-FIBER STUDY USING BIOCYTIN AS AN ANTEROGRADE TRACER

This study describes the axonal projections of single thalamic reticul ar (TR) neurons within the visual thalamus in rats. Experiments were p erformed under urethane anesthesia and reticular cells were labeled by extracellular or juxtacellular microiontophoretic applications of bio cytin. The axonal arborizations of 19 TR cells projecting to the dorsa l lateral geniculate nucleus (DLG) or to the lateral dorsal/lateral po sterior complex (LD/LP) were reconstructed from serial horizontal sect ions. It was found that single TR cells projected within the limits of a single thalamic nucleus, either the DLG or the LD/LP complex, where their terminal fields formed rostrocaudally oriented rods (length: ap proximate to 800 mu m; diameter: approximate to 100 mu m) densely pack ed with grape-like boutons and varicosities. In addition, none of the labeled TR cells possessed recurrent axonal collaterals that ramified within the reticular complex itself. The functional implications of th ese morphological data for the synchronization of thalamic oscillation s are discussed.