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  1. Article ; Online: Volatile anesthetic effects on midbrain-elicited locomotion suggest that the locomotor network in the ventral spinal cord is the primary site for immobility.

    Jinks, Steven L / Bravo, Milo / Hayes, Shawn G

    Anesthesiology

    2008  Volume 108, Issue 6, Page(s) 1016–1024

    Abstract: Background: Volatile anesthetics produce immobility primarily by action in the spinal cord; however, anesthetic effects among different neuronal classes located in different spinal regions, and how they relate to immobility, are not understood.: ... ...

    Abstract Background: Volatile anesthetics produce immobility primarily by action in the spinal cord; however, anesthetic effects among different neuronal classes located in different spinal regions, and how they relate to immobility, are not understood.
    Methods: In decerebrated rats, effects of isoflurane and halothane on movement elicited by electrical microstimulation of the mesencephalic locomotor region (MLR) were assessed in relation to minimum alveolar concentration (MAC). Anesthetic effects on step frequency and isometric limb force were measured. The authors also examined effects of MLR stimulation on responses of nociceptive dorsal horn neurons and limb force responses to tail clamp.
    Results: Mean isoflurane requirements to block MLR-elicited stepping were slightly but significantly greater than MAC by 10%. Mean halothane requirements to block MLR-elicited stepping were greater than those for isoflurane and exceeded MAC by 20%. From 0.4 to 1.3 MAC (but not 0.0 to 0.4 MAC), there was a dose-dependent reduction in the frequency and force of hind limb movements elicited by MLR stimulation during both anesthetics. MLR stimulation inhibited noxious stimulus evoked responses of dorsal horn neurons by approximately 80%. Aptly, MLR stimulation produced analgesia that outlasted the midbrain stimulus by at least 15 s, as indicated by an 81% reduction in hind limb force elicited noxious tail clamp.
    Conclusions: Because electrical stimulation of the MLR elicits movement independent of dorsal horn activation, the immobilizing properties of isoflurane and halothane are largely independent of action in the dorsal horn. The results suggest that volatile anesthetics produce immobility mainly by action on ventral spinal locomotor networks.
    MeSH term(s) Anesthetics, Inhalation/pharmacology ; Animals ; Anterior Horn Cells/drug effects ; Dose-Response Relationship, Drug ; Halothane/pharmacology ; Immobilization/methods ; Isoflurane/pharmacology ; Locomotion/drug effects ; Male ; Mesencephalon/drug effects ; Mesencephalon/physiology ; Models, Animal ; Motor Neurons/drug effects ; Physical Stimulation/methods ; Posterior Horn Cells/drug effects ; Rats ; Rats, Sprague-Dawley ; Spinal Cord/drug effects ; Spinal Cord/physiology
    Chemical Substances Anesthetics, Inhalation ; Isoflurane (CYS9AKD70P) ; Halothane (UQT9G45D1P)
    Language English
    Publishing date 2008-08-13
    Publishing country United States
    Document type Journal Article ; Research Support, N.I.H., Extramural ; Research Support, Non-U.S. Gov't
    ZDB-ID 269-0
    ISSN 1528-1175 ; 0003-3022
    ISSN (online) 1528-1175
    ISSN 0003-3022
    DOI 10.1097/ALN.0b013e3181730297
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article ; Online: Brainstem regions affecting minimum alveolar concentration and movement pattern during isoflurane anesthesia.

    Jinks, Steven L / Bravo, Milo / Satter, Omar / Chan, Yuet-Ming

    Anesthesiology

    2010  Volume 112, Issue 2, Page(s) 316–324

    Abstract: Background: Spinal transection or selective delivery of volatile anesthetics to the spinal cord reduces minimum alveolar concentration (MAC), whereas precollicular decerebration does not. The authors sought to determine which brainstem regions influence ...

    Abstract Background: Spinal transection or selective delivery of volatile anesthetics to the spinal cord reduces minimum alveolar concentration (MAC), whereas precollicular decerebration does not. The authors sought to determine which brainstem regions influence anesthetic requirements and movement responses with isoflurane.
    Methods: Movement (biceps femoris electromyogram) and MAC were measured in adult rats before and after decerebration at the precollicular, mid-collicular, pontine or medullary level, or decerebellation. Additional experiments assessed the effects of lidocaine inactivation of the mesencephalic locomotor region on MAC and the effects of isoflurane on nociceptive neuronal responses in this region.
    Results: Transections placed at the level of the mid-colliculus, rostral pons, and pontomedullary junction significantly reduced MAC by approximately 10, 40, and 45%, respectively. MAC was decreased 9% after mid-medullary transections that were placed caudal to the nucleus raphe magnus but rostral to the dorsal reticular nucleus; however, only weak, single movements occurred. Caudal medullary transections at the obex decreased MAC by 60%. Bilateral inactivation of the mesencephalic locomotor region with lidocaine caused a reversible, 32% decrease in MAC and reduced the number and amplitude of movements at sub-MAC isoflurane concentrations. Neuronal responses of mesencephalic locomotor region neurons to supramaximal noxious tail clamp were reduced by 87% by 1.2 MAC isoflurane.
    Conclusions: The authors conclude that the mesencephalic locomotor region influences anesthetic requirements and promotes repetitive movement with sub-MAC isoflurane by facilitating ventral spinal locomotor circuits, where anesthetics seem to exert their key immobilizing effects. However, net brainstem influences on MAC seem to result from interaction among descending nociceptive and locomotor modulatory pathways.
    MeSH term(s) Anesthesia ; Anesthetics, Inhalation/pharmacology ; Anesthetics, Local/administration & dosage ; Anesthetics, Local/pharmacology ; Animals ; Brain Stem/cytology ; Brain Stem/drug effects ; Brain Stem/physiology ; Electromyography ; Isoflurane/pharmacology ; Lidocaine/administration & dosage ; Lidocaine/pharmacology ; Locomotion/physiology ; Male ; Microinjections ; Movement/drug effects ; Neural Pathways/drug effects ; Neurons/drug effects ; Physical Stimulation ; Pulmonary Alveoli/metabolism ; Rats ; Rats, Sprague-Dawley
    Chemical Substances Anesthetics, Inhalation ; Anesthetics, Local ; Lidocaine (98PI200987) ; Isoflurane (CYS9AKD70P)
    Language English
    Publishing date 2010-01-25
    Publishing country United States
    Document type Journal Article ; Research Support, N.I.H., Extramural ; Research Support, Non-U.S. Gov't
    ZDB-ID 269-0
    ISSN 1528-1175 ; 0003-3022
    ISSN (online) 1528-1175
    ISSN 0003-3022
    DOI 10.1097/ALN.0b013e3181c81319
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  3. Article: Responses of bronchial C-fiber afferents of the rabbit to changes in lung compliance.

    Ma, Amy / Bravo, Milo / Kappagoda, C Tissa

    Respiratory physiology & neurobiology

    2003  Volume 138, Issue 2-3, Page(s) 155–163

    Abstract: Rapidly adapting receptors (RAR) in the lung are stimulated when the lung compliance is reduced. The present investigation was undertaken to determine whether bronchial C-fibers are also activated when lung compliance is decreased since both RAR and ... ...

    Abstract Rapidly adapting receptors (RAR) in the lung are stimulated when the lung compliance is reduced. The present investigation was undertaken to determine whether bronchial C-fibers are also activated when lung compliance is decreased since both RAR and bronchial C-fibers are influenced by extra-vascular fluid in the airways. Action potentials (AP) were recorded from bronchial C, pulmonary C, RAR and slowly adapting receptor (SAR) afferents in the cervical vagus in open chest New Zealand White rabbits ventilated at a constant rate and tidal volume. AP were recorded during (a) positive end-expiratory pressure (PEEP) of 2-3 cmH2O (control), (b) zero end-expiratory pressure (ZEEP), (c) negative end-expiratory pressure (NEEP) of -4 cmH2O, (d) restoration of PEEP and (e) final control after hyper-inflation. Both RAR and bronchial C-fiber activity increased significantly compared with control when lung compliance was decreased (bronchial C-fibers: 35 +/- 5 vs. 66 +/- 13 impulses per 30 sec and RAR: 3 +/- 1 vs. 94 +/- 14 impulses per 30 sec).
    MeSH term(s) Action Potentials/physiology ; Animals ; Blood Pressure ; Heart Rate ; Lung/metabolism ; Lung Compliance/physiology ; Male ; Nerve Fibers, Unmyelinated/physiology ; Positive-Pressure Respiration/methods ; Pulmonary Stretch Receptors/physiology ; Rabbits ; Reflex/physiology ; Tidal Volume/physiology ; Trachea/innervation ; Trachea/physiology
    Language English
    Publishing date 2003-11-04
    Publishing country Netherlands
    Document type Comparative Study ; Journal Article ; Research Support, U.S. Gov't, P.H.S.
    ZDB-ID 2077867-3
    ISSN 1878-1519 ; 1569-9048
    ISSN (online) 1878-1519
    ISSN 1569-9048
    DOI 10.1016/s1569-9048(03)00189-7
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  4. Article: Responses of C fiber afferents of the rabbit airways and lungs to changes in extra-vascular fluid volume.

    Gunawardena, S / Ravi, K / Longhurst, J C / Kaufman, M P / Ma, Amy / Bravo, Milo / Kappagoda, C T

    Respiratory physiology & neurobiology

    2002  Volume 132, Issue 3, Page(s) 239–251

    Abstract: Effects of changes in extra-vascular fluid volume produced by pulmonary lymphatic obstruction and plasmapheresis on the activities of bronchial and pulmonary C fiber receptors and rapidly adapting receptors (RARs) were investigated in New Zealand White ... ...

    Abstract Effects of changes in extra-vascular fluid volume produced by pulmonary lymphatic obstruction and plasmapheresis on the activities of bronchial and pulmonary C fiber receptors and rapidly adapting receptors (RARs) were investigated in New Zealand White rabbits. In intact rabbits, pulmonary lymphatic obstruction either alone or in combination with plasmapheresis did not stimulate pulmonary C fiber receptors. Only the combined stimulus activated the bronchial C fiber receptors. Bronchial C fiber receptors were also stimulated by graded increases in left atrial pressure (+5 and +10 mmHg). In contrast, RARs were activated by lymphatic obstruction either alone or in combination with plasmapheresis. These procedures increase the extra-vascular fluid volume in the carina and bronchi but not in the lungs (alveoli). In rabbits with chronic pulmonary venous congestion secondary to mitral valve damage, bronchial C fiber receptors were not stimulated by these increments in left atrial pressure which were insufficient to increase the extra vascular fluid content of the airways. However, both pulmonary and bronchial C fiber receptors were stimulated when the left atrial pressure was raised to 25 mmHg in these animals to cause pulmonary edema.
    MeSH term(s) Adaptation, Physiological ; Afferent Pathways/physiology ; Airway Obstruction/physiopathology ; Animals ; Electrophysiology ; Lymphatic System/physiopathology ; Male ; Mitral Valve Insufficiency/physiopathology ; Nerve Fibers, Unmyelinated/physiology ; Plasmapheresis/methods ; Pulmonary Artery/physiology ; Pulmonary Artery/physiopathology ; Pulmonary Edema/physiopathology ; Pulmonary Stretch Receptors/physiopathology ; Rabbits ; Venous Cutdown ; Venous Pressure
    Language English
    Publishing date 2002-09-04
    Publishing country Netherlands
    Document type Comparative Study ; Journal Article ; Research Support, U.S. Gov't, P.H.S.
    ZDB-ID 2077867-3
    ISSN 1878-1519 ; 1569-9048
    ISSN (online) 1878-1519
    ISSN 1569-9048
    DOI 10.1016/s1569-9048(02)00114-3
    Database MEDical Literature Analysis and Retrieval System OnLINE

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