NUCLEUS RETROAMBIGUOUS PROJECTIONS TO LUMBOSACRAL MOTONEURONAL CELL GROUPS IN THE MALE CAT

Recently, in the female cat, nucleus retroambiguus (NRA) projections h ave been described as distinct motoneuronal cell groups in the lumbar enlargement, possibly involved in lordosis behavior. The present study deals with the NRA-lumbosacral pathway in the male cat, Lumbosacral i njections of wheat germ agglutinin-horseradish peroxidase (WGA-HRP) we re made to localize and quantify retrogradely labeled neurons in the c audal medulla. These injections were preceded by spinal hemisections t o distinguish between neurons with ipsi- and contralaterally descendin g axons. The NRA-lumbosacral fibers descended almost exclusively contr alaterally, but neurons in areas surrounding the NRA projected mainly ipsilaterally. Injections of WGA-HRP were made in the region of the NR A to determine its targets in the lumbosacral cord. To distinguish bet ween the contralateral NRA pathways and the ipsilateral projections fr om neurons in the adjoining lateral tegmentum, the injections were pre ceded by ipsilateral hemisections in C2. A new scaling method was used to compare the results of the different cases, despite variations in size and segmental organization. The results show that the distributio n pattern of anterogradely labeled fibers in the lumbosacral cord matc hed precisely the location of certain motoneuronal cell groups. The NR A projected densely to the abdominal wall and pelvic floor motoneurons in Onuf's nucleus, moderately to adductor longus, semimembranosus, an d biceps femoris anterior motoneuronal cell groups, and only sparsely to iliopsoas and semitendinosus motoneuronal cell groups. Compared wit h the findings in the female, the NRA in the male cat projects more he avily to the biceps anterior and adductor longus and only sparsely to the iliopsoas and semitendinosus motoneuronal cell groups. These male- female differences are discussed. (C) 1997 Wiley-Liss. Inc.