THE LOCALIZATION OF PERIPHERAL EFFERENT AND ASCENDING PROJECTION NEURONS IN THE LUMBOSACRAL "VISCERAL FIELD" OF THE RAT——FLUORO-GOLD AND HRP TRACING STUDY / 解剖学报

ABSTRACT

In the present study, the fluoro-gold(FG) and horseradish peroxidase(HRP) combined tracing method was used to investigate the localization of parasympathetic preganglionic neurons and ascending projection neurons in lumbosacral spinal cord of the rat. FG was injected into the lateral parabrachial nucleus(PBL) or into Barrington's nucleus on one side, and HRP was applied to the contralateral pelvic nerve. The retrogradely FG-labeled neurons were found in bilateral "visceral field" at segments L_5-S_2, and the majority of them were concentrated in the intermediolateral nucleus (IML), and the dorsal commissural nucleus (DCN). In addition to these areas, some labeled neurons were also observed in bilateral lamina I and lateral spinal nucleus (LSN). The parasympathetic preganglionic neurons labeled with HRP were seen in the IML at segments L_6-S_1, occasionally appeared in the intercalated nucleus. In the IML area, HRP-labeled parasympathetic preganglionic neurons were located in its ventral part, however, the localization of FG-labeled neurons projected to the PBL and Barrington's nucleus were mainly found in the dorsal and dorsomedial part of the IML, and a few FG-labeled cells were scattered among HRP-labeled cells. Based on the present and other investigations, the nomenclature, organization and function of the IML and the composition of the LSN were discussed.