Effects of focal cooling in the ventrolateral medulla on chemoresponsiveness in dogs

Chonan, Tatsuya; Adams, E. M.; Euler, Curt von; Cherniack, Neil S.

doi:10.1016/0034-5687(90)90005-j

Cited by 7 publications

(3 citation statements)

References 18 publications

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“…Neuronal structures in rostral parts of the ventral bulbar surface (VBS) participate in the integration of various afferent signals addressed to the respiratory center, including signals from central chemoreceptors [3,4,7]. Stimulation of these structures in a bulbospinal preparation from neonatal rats evokes rhythmic discharges in the phrenic nerve [5].…”

Section: Abstract: Central Inspiratory Activity; Subretrofacial Areamentioning

confidence: 99%

Effect of bilateral destruction of the subretrofacial area on central inspiratory activity of the respiratory center and on the respiratory response to hypercapnia

1997

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Local bilateral destruction with 1 M glutamic acid of neuronal structures located between ventral surface of the medulla oblongata and the retrofacial nucleus (subretrofacial area) in rats increases the amplitude of pulses from the phrenic nerve and lowers respiratory rate. Hypercapnia does not affect the amplitude of phrenic nerve pulses but increases respiratory rate. It is suggested that the amplitude of central respiratory activity is regulated by the central chemoreceptors with participation of neuronal structures located in the subretrofacial area. Key Words: central inspiratory activity; subretrofacial area; hypercapniaSignals from the central chemoreceptors play a crucial role in generating the inspiratory activity of the respiratory center [6]. Neuronal structures in rostral parts of the ventral bulbar surface (VBS) participate in the integration of various afferent signals addressed to the respiratory center, including signals from central chemoreceptors [3,4,7]. Stimulation of these structures in a bulbospinal preparation from neonatal rats evokes rhythmic discharges in the phrenic nerve [5]. Previously, we showed that respiratory reactions are most pronounced upon electrical stimulation of zones located between the VBS and retrofacial nucleus [2]; however, physiological mechanisms of these reactions remained unclear. The objective of this study was to evaluate the role of rostral structures of the VBS in the responses of the respiratory center to hypercapnia.Department of Normal Physiology, State Medical University, Samara MATERIALS AND METHODSThe study was conducted on 20 randomly bred albino rats under Nembutal anesthesia (40 mg/kg). The VBS was exposed in a region extending from the C, to the level of exit of cranial nerves VII-VIII and located 4.0-4.5 mm lateral to the midline of the brain. Neuronal structures of the VBS were stimulated with bipolar tungsten electrodes (distance between the electrodes 50 g) using square pulses (100 Hz, 1 msec, 0.5-20 gA) delivered by an ELS-2 electrostimulator. Glutamic acid (I M solution) was applied to the VBS bilaterally using a glass electrode with a tip diameter of 1 mmL Hypercapnia was produced for 1 min with a gaseous mixture containing 7% CO,_ in 02. CO 2 was measured with a GAU-5 gas analyzer. The phrenic nerve activity (PNA) was determined with bipolar silver electrodes connected to an amplifying and integrated unit [11. The medulla oblongata was removed for examination after each test.

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Section: Abstract: Central Inspiratory Activity; Subretrofacial Areamentioning

confidence: 99%

Effect of bilateral destruction of the subretrofacial area on central inspiratory activity of the respiratory center and on the respiratory response to hypercapnia

1997

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“…This effect leads to the working hypothesis that the information from both chemosensitive fields (rostral and caudal areas) would converge within the inter mediate area, from where it would be relayed to the respiratory integrative network. Evi dence for central chemosensitive areas on the ventral medullary surface of other species has been also demonstrated (rat [4]; dog [5]) but so far nothing definitive is known about the H+ ion sensitivity characteristics of the ven tral brain stem surface of man. However, histopathological findings on the ventral medul lary surface of sudden infant death victims provide some hints that this area may play a vital role in man as well [ 1 ].…”

Section: Introductionmentioning

confidence: 99%

Brain Stem Chemosensitivity; Its Implication in Central Respiratory Regulation

et al. 1994

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Central brain stem chemosensitivity plays an essential role in acid-base regulation. The site of the chemosensitive neuronal elements has not yet been clearly established. To address this question, we used an in vitro adult guinea pig isolated brain stem preparation, maintained in survival conditions by intrabasilar and bath perfusions of Krebs solution saturated with 95% O₂ and 5% CO₂. Hypercapnic stimulation, produced by modifying the CO₂ concentration of the medium perfusing brain stem structures via the basilar perfusion system, increased the respiratory burst frequency recorded from the hypoglossal nerve. Hypercapnia evoked by ventral surface superfusion increased the respiratory burst amplitude. These data suggest that chemosensitive neuronal elements could be located at the ventral surface as well as in the deeper brainstem structures. However, their characteristics may be different.

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“…The role of central chemoreceptors in this activity remains unclear because these receptors have not been identified. Recent studies have shown that neuronal structures located in the rostral region of the ventral surface of medulla oblongata (ventral bulbar surface, VBS) probably fulfil a chemosensory function and exert a complex effect on the respiratory center [2,4]. The mechanism of this effect is poorly understood.…”

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Alterations of phrenic nerve activity caused by stimulation of neuronal structures in rostral area of ventral surface of the medulla oblongata

1997

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Electrical stimulation of neuronal structures in a rostral area of the ventral bulbar surface alters central inspiratory activity in anesthetized rats, augmenting the amplitude and velocity of this activity during the periods of its increase and plateau. The reactions are more pronounced in rats with transected vagal nerves. Blockade of pulmonary mechanoreceptors eliminates the influence of rostral neuronal structures only on the temporal" parameters of the plateau. Bilateral cooling of neuronal structures to 20~ results in complete block of central inspiratory activity. Key Words: rostral region of ventral bulbar structure; central inspiratory activity; respiratory centerCentral inspiratory activity (CIA) of the respiratory center forms under the influence of specific afferent pulses from chemo-and mechanoreceptors [6,71. The role of central chemoreceptors in this activity remains unclear because these receptors have not been identified. Recent studies have shown that neuronal structures located in the rostral region of the ventral surface of medulla oblongata (ventral bulbar surface, VBS) probably fulfil a chemosensory function and exert a complex effect on the respiratory center [2,4]. The mechanism of this effect is poorly understood. The purpose of the present study was to evaluate the role of the rostral region of the VBS in the mechanisms through which the CIA of the respiratory center is formed. MATERIALS AND METHODSThe study was carried out on 58 Nembutal-anesthetized (35 mg/kg) rats (body weight 200-250 g) with intact (n=36) or cut (n=22) vagal nerves. The VBS was exposed from the C1 level to the level of Department of Normal Physiolo9% State Medical University, Samara exit of roots of cranial nerves VI-VII and 4.0-4.5 mm lateral to the midline. Rostral neuronal structures of the VBS were stimulated via bipolar electrodes (interelectrode distance 100 g) with square pulses (100 Hz, 1 msec, 0.5-20 gA) delivered by an ESU-2 electrostimulator. Neuronal structures were cooled to 20~ unilaterally or bilaterally with a thermode. Electrical activity of the phrenic nerve was measured with bipolar silver electrodes, amplified, and integrated using standard equipment [1]. Arterial blood pressure was recorded with an ID-2I apparatus. The results were statistically analyzed by Student's t test with comparison of the means. RESULTSNeuronal structures of the VBS were electrically stimulated, with a step of 1 mm, at levels from the middle of cranial nerve XII roots to the exit of nerve VI roots (Fig. 1). A neurogram with its envelope showing variations of the phrenic nerve activity (PNA) before and after electrical stimulation is shown in Fig. 2. This activity changed, upon stimulation of a limited zone within the rostral region of the VBS.

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Effects of focal cooling in the ventrolateral medulla on chemoresponsiveness in dogs

Cited by 7 publications

References 18 publications

Effect of bilateral destruction of the subretrofacial area on central inspiratory activity of the respiratory center and on the respiratory response to hypercapnia

Effect of bilateral destruction of the subretrofacial area on central inspiratory activity of the respiratory center and on the respiratory response to hypercapnia

Brain Stem Chemosensitivity; Its Implication in Central Respiratory Regulation

Alterations of phrenic nerve activity caused by stimulation of neuronal structures in rostral area of ventral surface of the medulla oblongata

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