J. Berndt

A superficial substrate on the ventral surface of the medulla oblongata influencing respiration

SummaryThe medulla oblongata of cats anesthetized with Chloralose-Urethane was electrically stimulated with a unipolar electrode (rectangular impulses 40/sec; 1 msec; 1–4 V) from the lower pons to C1–C2. Beginning at the ventral surface all points were stimulated at distances of 0.1–0.2 mm up to a depth of 1 mm, thereafter at millimeter intervals up to a depth of 6 mm below the surface. Ventilation, expiratoryPCO2 and arterial pressure were recorded.1.As has been demonstrated earlier by Loeschckeet al. (1970) stimulation of two separate areas on the ventral medullary surface caused increase in tidal volume, respiratory frequency and arterial pressure, the latter not without exception.2.In the more caudal area medial of the hypoglossal roots the response to electrical stimulation was strongest at the surface or not more than 0.2 mm below the surface. The response decreased with increasing distance from the surface until at a depth of 0.6–0.8 mm no or only a minimal response was observed. In 2 to 3 mm depth either a second rise in the rhythmic ventilatory response or a maintained forced inspiration was evoked, while stimulation at still deeper location was followed by a decrease of the tidal volume or by respiratory arrest in expiratory position.3.In the more rostral area, the response pattern in the more superficial layer was similar but less marked.4.It is suggested that one type of substrates responding to stimulation is confined to two thin layers at the ventral surface of the medulla oblongata and that these structures are involved in the drive of ventilation and of vasomotor tone. Their location is similar to the location of chemosentitivity as described by Schläfkeet al. (1970) and it seems possible that they play a role either in the origin or the transmission of chemosensitive impulses. Other substrates showing respiratory responses of the inspiratory or expiratory type are located deeper in the medulla oblongata and well demarcated from the described superficial substrates. They include the respiratory centres.

Histological Structures in the Chemosensitive Regions on the Ventral Surface of the Cat's Medulla oblongata*

SummaryThe region on the ventral surface of the medulla oblongata (see preceding communication) responding maximally to both electrical and chemical stimulation by inducing an increase of ventilation was marked electrolytically and examined histologically. A characteristic group of large multipolar nerve cells was always found at the spot marked by electrolysis.These cells are located medial to the hypoglossal roots and ventral to the inferior olive which separates them from the respiratory centers. The cells are distributed at a distance of 8–450 μm from the ventral surface of the medulla oblongata, the greatest concentration being located at 150–200 μm beneath the surface.The possible role of these cells in the central chemical respiratory drive is discussed.

Topography of the respiratory responses to electrical stimulation in the medulla oblongata

SummaryThe medulla oblongata of cats was exposed from the ventral surface and the effects of superficial and intramedullary submaximal stimulation with a unipolar electrode (40/sec, 1 msec, 1–4 V) on respiration were investigated. The response pattern was analysed with respect to reaction types. The observed ventilatory response was then mapped into medullary sections.Confirming the evidence of the older literature it was thus demonstrated that the ‘respiratory center’ may be functionally demarcated into ‘inspiratory’ and ‘expiratory’ structures. New data on their locations are presented. At the transition between them there was some overlapping of the effects. The data suggest, however, macroscopic grouping of inspiratory and of expiratory structures rather than a mixing of inspiratory and expiratory units on a cellular level as may have been concluded from some studies of the spike activity.

Interaction of central and peripheral respiratory drives in cats. II. Peripheral and central interaction of hypoxia and hypercapnia.

AbstractIn cats anesthetized with chloralose-urethane the blood supply to the right carotid body was performed by an extracorporal circuit containing a supporting pump and a membrane oxygenator. Inlet and outlet of the circuit were connected to the central and the peripheral end, resp., of the dissected right common carotid artery. By exposure of the circuit blood to different gas mixtures in the membrane oxygenator,

Untersuchungen zum zentralen chemosensiblen Mechanismus der Atmung

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Untersuchungen zum zentralen chemosensiblen Mechanismus der Atmung@@@Studies on the central chemosensitive mechanism of respiration: II. Die Steuerung der Atmung durch das extracellulre pH im Gewebe der Medulla oblongata@@@II. Control of respiration by the extracellular pH in medullary tissue

and

[Respiratory response to isolated changes of cerebrospinal fluid pH: studies of anesthetized and decerebrate cats before and during vagus nerve blockade].

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