Transneuronal tracing of neural pathways controlling an abdominal muscle, rectus abdominis, in the ferret

Abdominal muscles participate in generating a large number of behaviors and reflex responses, including expiration, coughing, sneezing, vomiting, post ural control, production of speech, straining, facilitation of venous retur n to the heart, and reaction to vestibular stimulation. However, the only p remotor neurons that have been conclusively shown to influence abdominal mo toneurons are located in nucleus retroambiguus, the expiratory region of th e caudal ventral respiratory group. In the present study, the neural circui try controlling the activity of one abdominal muscle, rectus abdominis, was mapped using the transneuronal tracer pseudorabies virus (PRV) in the ferr et. Injections of PRV into rectus abdominis labeled large presumed motoneur ons in the ventral horn of T-12-L-4 and smaller presumed interneurons that were scattered in laminae VII, VIII, IX, and X of T-4-L-4. In addition, neu rons in several areas of the medulla and caudal pens, including the retroam bigual nucleus, medial and ventromedial reticular formation, nucleus prepos itus hypoglossi, vestibular nuclei, and raphe nuclei, were infected by tran synaptic passage of PRV from rectus abdominis motoneurons. Thus, the multif unctional roles of abdominal muscles appear to be coordinated by premotor n eurons located in both the spinal cord and several regions of the brainstem . (C) 1999 Elsevier Science B.V. All rights reserved.