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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Pflügers Archiv 332 (1972), S. 146-170 
    ISSN: 1432-2013
    Keywords: Cerebrospinal Fluid ; Control of Respiration ; Central Chemoreceptors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In cats lightly anesthetized with chloralose-urethane, vagal and carotid nerves dissected, the ventral surface of the medulla oblongata was perfused with mock CSF solutions. The pH of the fluids was varied by altering either the bicarbonate concentration or the CO2 pressure. During each period of perfusion steady stateP A CO2 response curves of respiration were recorded. Tidal volume, respiratory frequency, and ventilation were plotted against a) the alveolar CO2 pressure, b) the pH of the perfusion fluids (pHCSF), and c) the pH in the extracellular space of the medulla (pHe). pHe was calculated from the acid base parameters of the blood and the mock CSF by means of a mathematical model described by Berndt, Berger and Mückenhoff (1972). Under the conditions specified above respiration was neither a unique function ofP A CO2 nor of pHCSF. In a single experiment, severalP A CO2 response curves could be recorded, the number and position of which depended upon the number and the composition of the fluids simultaneously applied to the medullary surface. Similarly, pHCSF response curves could be constructed, the position and course of which was determined by theP A CO2. On the other hand, respiration could be shown to be an almost unique function of the medullary extracellular pH—irrespective of whether pHe was changed by alteringP A CO2 or pHCSF—ifV T or  were platted against the pHe values located at a depth of 200–400 μm below the ventral medullary surface. A worse correlation was obtained between respiration and pHe at smaller or greater depth. It is concluded that the effects on respiration of changes in the CO2 pressure of the blood or in the bicarbonate concentration and the CO2 pressure of the CSF can be explained by their influence on the extracellular hydrogen ion concentration in the medulla. The chemosensitive structures responding to the hydrogen ion concentration have to be assumed at a location less than 1 mm below the ventral medullary surface.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Pflügers Archiv 332 (1972), S. 184-197 
    ISSN: 1432-2013
    Keywords: Control of Respiration ; Central Chemoreceptors ; Decerebration ; Anesthesia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The ventilatory response to changes in the extracellular pH in the medullary tissue (pH e ) was studied in decerebrate cats and in cats anesthetized with chloralose-urethane. pH e was varied by changing theP ACO2 and by perfusion of the ventral medullary surface with solutions of different bicarbonate concentrations. For comparison,P ACO2 response curves of respiration were recorded in the decerebrate animals without simultaneous perfusion. 1. TheP ACO2 response curves ofV T obtained during perfusion of the ventral medullary surface with mock CSF show a smaller slope than the control curves recorded without perfusion. 2. The frequency response to changes inP ACO2 resembles the response obtained under control conditions only during alkaline perfusion (pH 7.6–7.8). More acid perfusates cause a decrease of frequency, which is probably due to their effect on calcium ionization. 3. During perfusion, ventilation does not reach the maximal values observed under control conditions. This is mainly caused by the diminished frequency response. 4. A similar behaviour ofV T ,f andV is observed in anethetized cats. However,f andV, less obviouslyV T , are distinctly diminished as compared with the decerebrate animals. 5. The pH e -response ofV T is not diminished during anesthesia, which is attributed to a local wash-out ot the narcotics by the perfusion. Frequency response and ventilatory response, however, are reduced as compared with decrerebrate cats.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Pflügers Archiv 332 (1972), S. 171-183 
    ISSN: 1432-2013
    Keywords: Control of Respiration ; Central Chemoreceptors ; Vagus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In cats lightly anesthetized with chloralose-urethane, the respiratory response to changes in the medullary extracellular pH (pH e ) was studied before and after cervical vagotomy. pH e was varied by perfusion of the ventral medullary surface with mock CSF of different pH (pHCSF) and by changes inP ACO2; it was calculated from the acid-base parameters of the blood and the mock CSF by means of a mathematical model described by Berndt, Berger, and Mückenhoff (1972). Results. 1. The hydrogen ion concentration in the CSF does not influence respiration at pHCSF values below 6.5. 2. An increase of ventilation as a response to increasing extracellular hydrogen ion concentration is only obtained in a pH e range of about 0.2 pH units, which under the conditions of the present experiments lay between pH e 7.1 and 7.3, due to the methods of calculation employed. pH e -values below 7.1 usually caused a decrease in ventilation. 3. Vagotomy influences the response of the tidal volume and the respiratory frequency to changes in pH e : the tidal volume is increased after vagotomy and the slope of the pH e -response curve ofV T is steeper, while the frequency decreases and further diminishes with decreasing pH e . The average response of ventilation, however, is not significantly altered after vagotomy. This confirms the hypothesis that in the case of the central chemical control of respiration the vagal activity is responsible for the partition of the total response to chemical stimuli into partial responses ofV T andf rather than for the magnitude of the total ventilatory response.
    Type of Medium: Electronic Resource
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