Immunocytochemical studies of the lateral cervical and lateral spinal nuclei

s130 IMMUNOCYTOCHEMICAL STUDIES OF THE LATEKAL CERVICAL AND LATERAL SPINAL NUCLEI. G.J. Giesler, Jr. and R.P. Elde*, Dept. of Anatomy, Univ. Minn., Minneapolis, Mn 55455, USA __ The lateral cervical nucleus (LCN) is the terminus of the nociceDtive uathway, the spinocervical tract, and'projects heavily to the thalamis. It is thus thought to be importantly involved in nociception in the cat. The cat LCN is located in the dorsal lateral funiculus (DLF) of seclments Cl and 2. In the rat, neurons are found in the DLF at all'levels of the spinal cord. Early workers suggested that this entire nucleus in the rat DLF might be the homologue of the LCN. We reported however, that DLF neurons in C2 of the rat differ from DLF neurons in the remainder of the cord in both their response characteristics and projections. Since anatomically and physiologically DLF neurons in C2 are very similar to cat LCN cells, we suggested that they constitute the previously overlooked rat LCN. To distinguish them from LCN neurons, DLF neurons in other segments are referred to as the lateral spinal nucleus (LSN). We now report studies in which the peptidergic content of fibers in these two nuclei has been compared using Antibodies raised against indirect fluorescent antibody techniques. dynorphin 1-8 and substance P produced dense labeling of fibers in apposiClearly visible but less dense tion to LSN neurons at all spinal levels. labeling was produced in fibers within LSN by antibodies against menkephalin, somatostatin, FMRF-NH2. Several other compounds, including neurotensin, 5-HT, VIP, CCK, CRF and oxytocin, were found in very few, if very few labeled fibers were found in any, fibers in LSN. In contrast, These observations were confirmed LCN regardless of the antibody employed. in a blind rating procedure. We have also examined fibers within LCN of Like those in the rat LCN, fibers in the cat LCN are only rarely the cat. immunostained with antibodies raised against any of the above compounds. Supported by NS 17540 and DA 02148. DOUBLE LABELING OF CAT SPINAL DORSAL HORN NEURONS WITH 191 Slide FLUORESCENT SUBSTANCES. S.S. Jiao*, G.F. Zhang*, Y.J. Liu*, Sun 3:45 Y.S. Wang* and G.W. Lu, Department of Anatomy and Neuror Vashon ~~ --I~: physiology, Beijing Second Medical College, Beijing, China. Spinal dorsal horn neurons (SDHN) have been implicated in mechanisms of pain. Physiological evidence has been presented for SDHN with branched axons ascending both the dorsal and dorsolateral funiculi. The present study is aimed at doubly labeling the cells of origin of the SDHN system. Fast blue (FB) was injected within unilateral gracile nucleus (GN) of adult cats anesthetized with pentobarbital. Nuclear yellow (NY) was injected ipsilaterally within the lateral cervical nucleus (LCN) 8-9 days later. After an additional 18-30 hrs. of survival, the cats were sacrificed and perfused. The spinal cords were sectioned and viewed on a fluorescence microscope. The sections were then counterstained with Nissl's method. Most neurons labeled with both FB and NY were located mainly in Laminae III, IV and V of the dye-injected side throughout Ll-S3. These neurons At ipsilateral L6-7 level, a few were large in size and polygonal in form. double-labeled cells, which were small spindle-shaped, were also found in Lamina I. Neurons labeled with only FB or NY were situated primarily in Laminae IV, V and VI of the same side of segments Ll-S3. The findings demonstrate morphologically the existence of individual SDHN with branched axons projecting to both the GN and LCN. These neurons are thought to be involved in somatosensory function and the mechanisms of pain activation and modulation in particular.