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This Article Full Text Full Text (PDF) All Versions of this Article: 94/4/2617    most recent 00370.2005v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Web of Science (3) Citing Articles via Google Scholar Google Scholar Articles by Boers, J. Articles by Kirkwood, P. A. Search for Related Content PubMed PubMed Citation Articles by Boers, J. Articles by Kirkwood, P. A.

Functional Heterogeneity Among Neurons in the Nucleus Retroambiguus With Lumbosacral Projections in Female Cats

¹Sobell Department of Motor Neuroscience and Movement Disorders, Institute of Neurology, University College London, London, United Kingdom; ²Department of Anatomy and Embryology, Faculty of Medicine, University of Groningen, Groningen, The Netherlands; and ³University of Nottingham School of Nursing, Queen's Medical Centre Nottingham, United Kingdom

Submitted 11 April 2005; accepted in final form 10 June 2005

Nucleus retroambiguus (NRA), in the caudal medulla, projects to all spinal levels. One physiological role is abdominal pressure control, evidenced by projections to intercostal and abdominal motoneurons from expiratory bulbospinal neurons (EBSNs) within NRA. The roles of NRA projections to the lumbosacral cord are less certain, although those to limb motoneurons may relate to mating behavior and those to Onuf's nucleus (ON) to maintaining continence. To clarify this we physiologically characterized NRA projections to the lumbosacral cord. Extracellular recordings were made in NRA under anesthesia and paralysis in estrus cats. Administered CO₂ gave a strong respiratory drive. Antidromic unit responses were recorded to stimulation of the contralateral ventrolateral funiculus of L₆, L₇, or sacral segments and to microstimulation in the region of semimembranosus motor nucleus or ON. All units were found at sites showing expiratory discharges. Units that showed collisions between antidromic and spontaneous spikes (all in late expiration) were identified as EBSNs. These were common from the ventrolateral funiculus (VLF) of L₆ (42.5%) or L₇ (32.9%), but rare from the sacral VLF or the motor nuclei. Antidromic latencies revealed a subthreshold respiratory drive in some non-EBSNs. This group had lower conduction velocities than the EBSNs. The remainder, with a negligible respiratory drive, had even lower conduction velocities. A new population of NRA neurons has thus been defined. They are not active even with a strong respiratory drive, but may provide most of the synaptic input from NRA to lower lumbar and sacral segments and could subserve functions related to mating behavior.