Physiology of Neuronal Subtypes in the Respiratory-Vocal Integration Nucleus Retroamigualis of the Male Zebra Finch

• Published in: Journal of neurophysiology Vol. 94; no. 4; pp. 2379 - 2390
• Main Authors: Kubke, M. F, Yazaki-Sugiyama, Y, Mooney, R, Wild, J. M
• Format: Journal Article
• Language: English
• Published: United States Am Phys Soc 01.10.2005
• Subjects: Action Potentials - physiology; Animals; Electric Stimulation - methods; Finches; Functional Laterality; Immunohistochemistry; In Vitro Techniques; Male; Microscopy, Confocal - methods; Multivariate Analysis; Neural Pathways - cytology; Neural Pathways - physiology; Neurons - classification; Neurons - physiology; Principal Component Analysis; Reaction Time; Receptors, Glycine - metabolism; Respiration; Respiratory Center - cytology; Respiratory Muscles - physiology; Taeniopygia guttata; Time Factors; Vocalization, Animal - physiology
• ISSN: 0022-3077; 1522-1598
• DOI: 10.1152/jn.00257.2005

1 Division of Anatomy, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand; and 2 Department of Neurobiology, Duke University Medical Center, Durham North Carolina Submitted 10 March 2005; accepted in final form 28 May 2005 Learned vocalizations, such as bird song, require intricate coordination of vocal and respiratory muscles. Although the neural basis for this coordination remains poorly understood, it likely includes direct synaptic interactions between respiratory premotor neurons and vocal motor neurons. In birds, as in mammals, the medullary nucleus retroambigualis (RAm) receives synaptic input from higher level respiratory and vocal control centers and projects to a variety of targets. In birds, these include vocal motor neurons in the tracheosyringeal part of the hypoglossal motor nucleus (XIIts), other respiratory premotor neurons, and expiratory motor neurons in the spinal cord. Although various cell types in RAm are distinct in their anatomical projections, their electrophysiological properties remain unknown. Furthermore, although prior studies have shown that RAm provides both excitatory and inhibitory input onto XIIts motor neurons, the identity of the cells in RAm providing either of these inputs remains to be established. To characterize the different RAm neuron types electrophysiologically, we used intracellular recordings in a zebra finch brain stem slice preparation. Based on numerous differences in intrinsic electrophysiological properties and a principal components analysis, we identified two distinct RAm neuron types (types I and II). Antidromic stimulation methods and intracellular staining revealed that type II neurons, but not type I neurons, provide bilateral synaptic input to XIIts. Paired intracellular recordings in RAm and XIIts further indicated that type II neurons with a hyperpolarization-dependent bursting phenotype are a potential source of inhibitory input to XIIts motor neurons. These results indicate that electrically distinct cell types exist in RAm, affording physiological heterogeneity that may play an important role in respiratory–vocal signaling. Address for reprint requests and other correspondence: M. F. Kubke, Div. of Anatomy, Faculty of Medical and Health Sciences, Univ. of Auckland, Private Bag 92019, Auckland, New Zealand (E-mail: f.kubke{at}auckland.ac.nz )