Transneuronal tracing of neural pathways that regulate hindlimb muscle blood flow

• Published in: American journal of physiology. Regulatory, integrative and comparative physiology integrative and comparative physiology, 2007-04, Vol.292 (4), p.R1532-R1541
• Main Authors: Lee, T.-K, Lois, J. H, Troupe, J. H, Wilson, T. D, Yates, B. J
• Format: Article
• Language: English
• Subjects: Animals; Blood pressure; Cardiovascular system; Herpesvirus 1, Suid - genetics; Herpesvirus 1, Suid - physiology; Hindlimb - blood supply; Hindlimb - innervation; Immunohistochemistry; Lumbar Vertebrae; Male; Medulla Oblongata - cytology; Medulla Oblongata - physiology; Mesencephalon - cytology; Mesencephalon - physiology; Muscle, Skeletal - blood supply; Muscle, Skeletal - innervation; Muscle, Skeletal - physiology; Musculoskeletal system; Neural Pathways - physiology; Neurons; Neurons - cytology; Neurons - enzymology; Neurons - physiology; Neurons - virology; Neurotransmitters; Pons - cytology; Pons - physiology; Pseudorabies virus; Rats; Rats, Sprague-Dawley; Spinal Cord - surgery; Swine; Sympathetic Nervous System - physiology; Tyrosine 3-Monooxygenase - metabolism; Viruses
• ISSN: 0363-6119; 1522-1490
• DOI: 10.1152/ajpregu.00633.2006

Departments of 1 Otolaryngology and 2 Neuroscience, University of Pittsburgh, Pittsburgh, Pennsylvania; 3 Department of Neurology, Soonchunhyang University College of Medicine, Bucheon City, Gyunggido, Republic of Korea; and 4 Faculty of Health Sciences, University of Western Ontario, London, Ontario, Canada Submitted 5 September 2006 ; accepted in final form 1 December 2006 Despite considerable interest in the neural mechanisms that regulate muscle blood flow, the descending pathways that control sympathetic outflow to skeletal muscles are not adequately understood. The present study mapped these pathways through the transneuronal transport of two recombinant strains of pseudorabies virus (PRV) injected into the gastrocnemius muscles in the left and right hindlimbs of rats: PRV-152 and PRV-BaBlu. To prevent PRV from being transmitted to the brain stem via motor circuitry, a spinal transection was performed just below the L2 level. Infected neurons were observed bilaterally in all of the areas of the brain that have previously been shown to contribute to regulating sympathetic outflow: the medullary raphe nuclei, rostral ventrolateral medulla (RVLM), rostral ventromedial medulla, A5 adrenergic cell group region, locus coeruleus, nucleus subcoeruleus, and the paraventricular nucleus of the hypothalamus. The RVLM, the brain stem region typically considered to play the largest role in regulating muscle blood flow, contained neurons infected following the shortest postinoculation survival times. Approximately half of the infected RVLM neurons were immunopositive for tyrosine hydroxylase, indicating that they were catecholaminergic. Many (47%) of the RVLM neurons were dually infected by the recombinants of PRV injected into the left and right hindlimb, suggesting that the central nervous system has a limited capacity to independently regulate blood flow to left and right hindlimb muscles. blood flow patterning; pseudorabies virus; exercise hyperemia Address for reprint requests and other correspondence: B. J. Yates, Univ. of Pittsburgh, School of Medicine, Dept. of Otolaryngology, Eye and Ear Institute, Rm. 519, Pittsburgh, PA 15213 (e-mail: byates{at}pitt.edu )