The Experts below are selected from a list of 732 Experts worldwide ranked by ideXlab platform
Refik Kanjhan - One of the best experts on this subject based on the ideXlab platform.
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electrophysiological study of Dorsal Respiratory neurons in the medulla oblongata of the rat
Brain Research, 1994Co-Authors: Denis De Castro, Janusz Lipski, Refik KanjhanAbstract:Abstract There has been controversy whether the Dorsal Respiratory Group (DRG), identified in the cat and several other species as a concentration of mainly inspiratory neurons located in the ventrolateral subnucleus of the solitary tract, also exists in the rat. The aim of this study was to re-examine this question by systematically exploring this region with extracellular microelectrodes, in anesthetized and artificially ventilated rats. One-hundred and forty-two units were recorded which fired in phase with central Respiratory cycles (determined by recording from the phrenic nerve) and/or lung inflations. One-hundred and nineteen recordings were thought to be from neuronal cell bodies (confirmed in some cases by excitatory responses to microelectrophoretic administration of dl -homocysteic acid), while the remaining 23 were from lung vagal afferents. Most neurons in the former Group (87/119) were inspiratory. Out of 96 neurons tested for spinal projections only 14 (12 inspiratory, 2 expiratory) responded antidromically following stimulation at C3 segment. These results confirm the existence of the DRG in the rat and demonstrate that neurons located in this region have firing patterns generally similar to those previously described in the cat. The main difference is the relative paucity in the rat of neurons projecting spinally below the C2 level, which indicates that most DRG neurons in this species do not project directly to phrenic and intercostal motoneurons, but to other, as yet unidentified, neuronal Groups within the brainstem or upper cervical segments.
Michael George Zaki Ghali - One of the best experts on this subject based on the ideXlab platform.
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Midbrain control of breathing and blood pressure: The role of periaqueductal gray matter and mesencephalic collicular neuronal microcircuit oscillators.
The European journal of neuroscience, 2020Co-Authors: Michael George Zaki GhaliAbstract:Neural circuitry residing within the medullary ventral Respiratory column nuclei and Dorsal Respiratory Group interact with the Kolliker-Fuse and medial parabrachial nuclei to generate the core breathing rhythm and pattern during resting conditions. Triphasic eupnea consists of inspiratory [I], post-inspiratory [post-I], and late-expiratory [E2] phases. Mesencephalic zones exert modulatory influences upon Respiratory rhythm-generating circuitry, sympathetic oscillators, and parasympathetic nuclei. The earliest evidence supporting the existence of midbrain control of breathing derives from studies conducted by Martin and Booker in 1878. These authors demonstrated electrical stimulation of the deep layers of the mesencephalic colliculi in the rabbit augmented ventilation and sequentially elicited chest wall tremors and tetany. Investigations performed during the past several decades would demonstrate stimlation of distributed zones within the midbrain reticular formation elicits starkly disparate effects upon Respiratory phase switching. Schmid, Bohmer, and Fallert demonstrated electrical stimulation of the nucleus rubre and emanating axon bundles alternately elicits or inhibits the activity of medullary expiratory- or inspiratory-related units and phrenic nerve discharge with differential latency. A series of studies would later indicate the red nucleus mediates hypoxic ventilatory depression. Periaqueductal gray matter neurons exhibit extensive afferent and efferent interconnectivity with suprabulbar, brainstem, and spinal cord zones aptly positioning these units to modulate breathing, autonomic outflow, nociception locomotion, micturtion, and sexual behavior. Experimental stimulatory activation of the tectal colliculi and periaqueductal gray matter via electrical current or glutamate, D,L-homocysteinic acid, or bicuculline microinjections coordinately modulates neuromotor inspiratory bursting frequency and amplitude and discharge of pre-Botzinger complex, ventrolateral medullary late-I and post-I, and ventrolateral nucleus tractus solitarius decrementing early-I and augmenting and decrementing late-I neurons, elicits expiratory outflow and vocalization, and blunt the Hering-Breuer reflex in unanesthetzed decerebrate and anesthetized preprations of the cat and rat. Stimulation of the mesencephalic colliuli or Dorsal divisions of the PAG potently amplifes renal sympathetic neural efferent activity, dynamic arterial pressure magnitude, and myocardial contraction frequency and elicits various behavioral defense responses. Elicited physiological effects exhibit extensive locoregional heterogeneity and variably enlist requisite contributions from the dorsomedial hypothalamus and/or lateral parabrachial nuclei. Stimulation of the Dorsal mesencephalon occasionally elicits dynamic increases of arterial pressure magnitude exhibiting prominent oscillatory variability coherent with phrenic nerve discharge, perhaps by generating intra-neuraxial hysteresis, serving to intermittently deliver blood to organ vascular beds under high pressure in order to prevent organ edema, microcirculatory dysfunction, and downregulation of vascular smooth muscle alpha adrenergic receptors. Chemosensitive mesencephalic caudal raphe units and projections of hypoxia-sensitive units in the caudal hypothalamus to the periaqueductal gray matter may imply the existence of a diencephalo-smesencephalic chemosensitive network modulating breathing and sympathetic discharge.
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Respiratory rhythm generation and pattern formation oscillators and network mechanisms
Journal of Integrative Neuroscience, 2019Co-Authors: Michael George Zaki GhaliAbstract:The Respiratory rhythm is generated by the interaction of oscillators disparately distributed throughout the pons, medulla, and spinal cord. According to the classic model, the interaction amongst preBotzinger complex (preBotzC) spontaneously bursting preinspiratory units and Botzinger complex (BotzC) expiratory cells generates the principal Respiratory rhythm, thence relayed caudally to the pattern generating elements and premotoneurons of the rostral and caudal divisions of the ventral Respiratory Group and bulbospinal units of the Dorsal Respiratory Group. Rhythm and pattern generating elements in the ventrolateral medulla receive powerful phasic and tonic modulatory inputs from diencephalic structures, midbrain, Kolliker-Fuse, and parabrachial nuclei, retrotrapezoid nucleus, parafacial Respiratory Group, ventrolateral metencephalon, nucleus tractus solitarius, and brainstem reticular formation, collectively shaping the normal eupneic discharge. Empirical and computational studies have generated models of Respiratory rhythmogenesis and pattern formation variously predicated upon pacemaker, network, or hybrid pacemaker network mechanisms to explain oscillatory behavior and regularity. Network mechanisms critically require the integrity and functionality of inhibitory synaptic neurotransmission. The operation and contribution of inhibitory elements in Respiratory rhythm generation and pattern formation are well demonstrated empirically and incorporated in computational network and hybrid models of breathing. Fast inhibitory synaptic neurotransmission utilizes GABAAergic and glycinergic mediated activation of receptor linked chloride conductances, generating an inwardly directed flux of chloride ions mediating membrane voltage hyperpolarization and is required to generate eupneic Respiratory patterns in vivo and situ. Persistence of rhythmicity in the presence of synaptic antagonism of GABAA and glycine receptor mediated fast inhibitory neurotransmission indicates pacemaker generating mechanisms sufficiently capable of independently generating this behavior in vivo and transected intact preparations maintaining the preBotzC as the most rostrally preserved structure. The role of GABAB receptor mediated neuromodulation in Respiratory rhythm generation and pattern formation is comparatively significantly less investigated. GABABergic activation of postsynaptic and presynaptic membrane receptors variably upregulates potassium conductances and downregulates calcium conductances. Respiratory rhythm and pattern are powerfully modulated in vivo, in situ, and in vitro by superfusion or localized microinjections of GABABergic agonists and antagonists, though are typically not abolished by these experimental interventions. Directionality and magnitude of these effects exhibit maturational changes. The relative depolarization of chloride reversal potentials during the early neonatal period, with gradual shifts towards normal hyperpolarizing values during development, suggests GABABergic signaling may mediate the inhibitory neurotransmission necessary to generate triphasic eupnea. We review and discuss the role of spontaneously bursting oscillators and network mechanisms predicating upon fast inhibitory synaptic neurotransmission in contributing to Respiratory rhythmogenesis and pattern formation.
Ikuo Homma - One of the best experts on this subject based on the ideXlab platform.
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Optical imaging of Respiratory neuron activity from the Dorsal view of the lower brainstem
Clinical and Experimental Pharmacology and Physiology, 2005Co-Authors: Hiroshi Onimaru, Ikuo HommaAbstract:1. We visualized Respiratory-related neuron network activity in the Dorsal part of the pons and medulla of an in vitro preparation from newborn rats by optical recordings using a voltage-sensitive dye. We measured optical signals from several seconds before to several seconds after the inspiratory phase using the inspiratory motor nerve discharge as the trigger signal and we averaged the optical signals of 20-50 Respiratory cycles to obtain an optical image correlating specifically to inspiratory activity. 2. Four areas that were excited or inhibited corresponding to the Respiratory cycles were detected. (i) The most rostral activity was in the rostral and lateral parts of the pons, with activity mainly in the inspiratory phase, corresponding to the pontine-Respiratory Group. (ii) In the midpontine level, inspiratory activity followed by long-lasting hyperpolarization appeared in the midlateral parts. This part was presumed to reflect activity in the locus coeruleus. The hyperpolarization became almost negligible after treatment with the alpha-adrenergic antagonist, phentolamine. (iii) In the Dorsal medulla, the predominantly inspiratory activity was detected at the rostral level of the area postrema. This part was considered to reflect activity mainly of the hypoglossal nucleus. (iv) At a similar level, we also detected weak and disperse inspiratory activity extending more laterally and caudally than that of the hypoglossal nucleus activity. This might reflect activity of the Dorsal Respiratory Group. 3. In conclusion, the present optical recording study revealed that the Dorsal part of the lower brainstem in the in vitro preparation is noticeably active as well as the ventral part shown in the previous study. This method is very useful for analysis of pharmacological properties, as well as the spatio-temporal pattern of Respiratory-related network activity in the brainstem.
Denis De Castro - One of the best experts on this subject based on the ideXlab platform.
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electrophysiological study of Dorsal Respiratory neurons in the medulla oblongata of the rat
Brain Research, 1994Co-Authors: Denis De Castro, Janusz Lipski, Refik KanjhanAbstract:Abstract There has been controversy whether the Dorsal Respiratory Group (DRG), identified in the cat and several other species as a concentration of mainly inspiratory neurons located in the ventrolateral subnucleus of the solitary tract, also exists in the rat. The aim of this study was to re-examine this question by systematically exploring this region with extracellular microelectrodes, in anesthetized and artificially ventilated rats. One-hundred and forty-two units were recorded which fired in phase with central Respiratory cycles (determined by recording from the phrenic nerve) and/or lung inflations. One-hundred and nineteen recordings were thought to be from neuronal cell bodies (confirmed in some cases by excitatory responses to microelectrophoretic administration of dl -homocysteic acid), while the remaining 23 were from lung vagal afferents. Most neurons in the former Group (87/119) were inspiratory. Out of 96 neurons tested for spinal projections only 14 (12 inspiratory, 2 expiratory) responded antidromically following stimulation at C3 segment. These results confirm the existence of the DRG in the rat and demonstrate that neurons located in this region have firing patterns generally similar to those previously described in the cat. The main difference is the relative paucity in the rat of neurons projecting spinally below the C2 level, which indicates that most DRG neurons in this species do not project directly to phrenic and intercostal motoneurons, but to other, as yet unidentified, neuronal Groups within the brainstem or upper cervical segments.
Hiroshi Onimaru - One of the best experts on this subject based on the ideXlab platform.
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Optical imaging of Respiratory neuron activity from the Dorsal view of the lower brainstem
Clinical and Experimental Pharmacology and Physiology, 2005Co-Authors: Hiroshi Onimaru, Ikuo HommaAbstract:1. We visualized Respiratory-related neuron network activity in the Dorsal part of the pons and medulla of an in vitro preparation from newborn rats by optical recordings using a voltage-sensitive dye. We measured optical signals from several seconds before to several seconds after the inspiratory phase using the inspiratory motor nerve discharge as the trigger signal and we averaged the optical signals of 20-50 Respiratory cycles to obtain an optical image correlating specifically to inspiratory activity. 2. Four areas that were excited or inhibited corresponding to the Respiratory cycles were detected. (i) The most rostral activity was in the rostral and lateral parts of the pons, with activity mainly in the inspiratory phase, corresponding to the pontine-Respiratory Group. (ii) In the midpontine level, inspiratory activity followed by long-lasting hyperpolarization appeared in the midlateral parts. This part was presumed to reflect activity in the locus coeruleus. The hyperpolarization became almost negligible after treatment with the alpha-adrenergic antagonist, phentolamine. (iii) In the Dorsal medulla, the predominantly inspiratory activity was detected at the rostral level of the area postrema. This part was considered to reflect activity mainly of the hypoglossal nucleus. (iv) At a similar level, we also detected weak and disperse inspiratory activity extending more laterally and caudally than that of the hypoglossal nucleus activity. This might reflect activity of the Dorsal Respiratory Group. 3. In conclusion, the present optical recording study revealed that the Dorsal part of the lower brainstem in the in vitro preparation is noticeably active as well as the ventral part shown in the previous study. This method is very useful for analysis of pharmacological properties, as well as the spatio-temporal pattern of Respiratory-related network activity in the brainstem.