Thalamic descendents from anterior and parafascicular nuclei to the brainstem. An experimental study using the HRP technique in the rat.

Method of HRP retrograde transport tracing (injections of 0.1 um 30% HRP, Sigma VI, in 17 rats) helped to prove the existence of a thalamo-raphe projection, part of which is the thalamo-reticular projection for the medial system of reticular formation. This projection takes its origin in the ncl. anteroventralis, ncl. anterodorsalis, ncl. parafascicularis and in the habenular nuclei. Terminations of the axons of those nuclei are situated in the ncl. centralis superior, ncl. raphealis dorsalis, ncl. tegmentalis ventralis et dorsalis Guddeni, substantia grisea centralis pontis, medial part of ncl. pontis oralis, area ventralis tegmenti Tsai and in the ncl. supramamillaris. Habenular nuclei project to the same area and also to the ncl. intercruralis. Thalamic descendents are in their termination field topographically arranged.