Ultrastructural evidence for direct excitatory retroambiguus projections to cutaneous trunci and abdominal external oblique muscle motoneurons in the cat (original) (raw)

The nucleus retroambiguus (NRA) is a group of neurons, located laterally in the caudal medulla oblongata. The NRA is thought to modulate abdominal pressure in the framework of respiration, vomiting, vocalization, probably parturition, and, in all likelihood mating behavior. The NRA exerts this control through its projections to motoneurons to the nucleus ambiguus in the lateral medulla (innervating pharynx, larynx), and spinal cord (innervating cutaneous trunci, intercostal, abdominal, pelvic floor, and lower limb muscles). The nature of these NRA-motoneuronal projections is unknown. In this study we have determined the ultrastructure of the NRA-motoneuronal projections, and especially those to the abdominal external oblique and cutaneous trunci muscles.