AFFERENT SOURCES OF SUBSTANCE-P IN THE C1 AREA OF THE RAT ROSTRAL VENTROLATERAL MEDULLA

To examine the potential extrinsic sources of substance P (SP)-contain ing terminals in the C1 area of the RVL, immunoperoxidase localization of SP was combined with retrograde transport of wheat germ agglutinin -conjugated horseradish peroxidase (WGA-HRP). In all cases examined, s everal neurons containing SP and WGA-HRP were found in the nucleus rap he pallidus and a few dual labeled neurons were found in the nucleus o f the solitary tract and the paraventricular nucleus of the hypothalam us. In some cases, one or two double labeled neurons were detected in the lateral hypothalamic area and nucleus raphe obscurus. The results demonstrate that although several brain structures contribute SP affer ents to the RVL, the nucleus raphe pallidus is the major extrinsic sou rce.