ROSTRAL RETICULAR NUCLEUS OF THE THALAMUS SENDS A PATCHY PROJECTION TO THE PULVINAR LATERALIS-POSTERIOR COMPLEX OF THE CAT

The pulvinar lateralis posterior complex (Pul-LP) and the reticular nu cleus of the thalamus (RE) are thought to be involved in visual and at tention-related tasks. This report provides data on the anatomical con nections between these two nuclei following the analysis of injections of horseradish peroxidase (HRP) + [H-3]leucine into the Pul-LP and RE of the cat. Following the retrograde transport of HRP from the Pul-LP , labeled cells were distributed in regions of the RE ventral to the c audate nucleus and adjacent to the stria terminalis between Horsley-Cl arke anterior-posterior (AP) coordinates 13.0 and 9.5 and more caudall y in areas dorsal and ventral to the lateral geniculate nucleus (LGN) between AP 9.0 and 4.5. The majority of the cell labeling within the R E following injections within the Pul-LP was seen dorsal to the latera l geniculate nucleus around AF 6.5-6.0. Cell labeling was heaviest fol lowing injections within the lateral LP in contrast to injections with in the Pul which resulted in fewer labeled cells. Autoradiographic ana lysis of the anterograde transport of leucine showed that the labeled Pul-LP fibers within the RE did not completely coincide with the distr ibution of HRP-labeled reticular cells from the same injection site. T his indicated a lack of strict reciprocity between these two nuclei. I n addition, injections of [H-3]leucine into dorsomedial areas of the R E near the rostral pole of the LGN resulted in a patchy distribution o f label within the Pul-LP which was most prominent as oblique dorsoven tral slabs across the thalamus. It was inferred that this distribution was along the borders between different subdivisions within the Pul-L P. The lack of strict reciprocity between the thalamic relay nuclei an d the reticular nucleus implies that areas of the Pul-LP may receive i nhibition from RE regions which they do not directly influence; this a natomical feature may provide a basis for selective inhibition of thal amic nuclei. (C) 1994 Academic Press, Inc.