低酸素症の臨床的ならびに実験的研究 : 実験編
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概要
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B) Experimental Observation All experiments were performed on random Kilo gram dogs anesthetized with sodium pentothal (30-50mg per Kilo intravenously); in minor experiments urethane was also used. Blood pressure was recorded from the femoral artery by mercury manometer, using 5000 units of Heparin as anticoagulant. Maintenance of artificial respiration was routine procedure, if specially indicated. Lung ventilation was maintained by means of a pump, the output of which was adjusted to a minute volume approximately equal the minute volume lung ventilation of the unoperated dog breathing air. To study cardio-vascular response to chemical stimulation the animals were subjected to the following conditions. 1. Oxygen deficiency is produced by attaching to the inlet of the respiratory pump Douglas bags containing oxygen-nitrogen gas mixtures with concentrations of oxygen ranging from 10-13%. The accuracy of gas mixture is checked periodically by gas analysis. 2. Carbon dioxide excess is produced by the administration of mixtures of room air and carbon dioxide. Concentrations of CO_2 ranging from 2.5-4.3% gas mixture containing a reduced oxygen tension and from 2.5-4.3% CO_2 are prepared and tested in a similar manner. The animals are subjected to the above conditions for periods of 15' to 17'. The carotid sinus pressoreceptoric reflex under control condition and in hypoxia is observed during and immediately, after H. E. Hering's second stimulation. After obtaining control reactions in the intact animal, the effect of eliminating the various chemoreceptor nerves is determined as follows: 1. Denervation of the carotid sinus region is performed by exstirpating carotid sinus nerve, stripping the adventitia of the external, internal, and common carotid arteries for one to two cm, on both sides of the sinus. This procedure is usually accompanied by a considerable rise of blood pressure.・. In the dog the cardioaortic nerve is combined with the vago-sympathetic trunk throughout most of its course. Therefore, vagotomy is used to diminute this nerve. In another series of experiments, the right aortic nerve is separated from the vagosympathetic trunk immediately under the branching point of recurrent nerve and in the left side the vagotomy is performed. The separationcal be tested by faradic stimulation of the nerve components. Stimulation of the peripheral end of the cut aortic nerve has no significant effect on blood pressure, whereas that of the central end causes a fall in blood pressure. 3. To locatecarotid body, the bifurcation of common carotid artery is exposed. This structure is visible as a reddish nodule firmly attached to the mesialsurface of a very small branch which arises either from the occipital artery near origin from the external carotid artery, or from the latter vessel itself. The carotid body is directly in the pathway of the nerve fibers from the carotid sinus, as these pass over the occipital artery on their way to join the glossopharyngeal nerve near the jugular. foramen. Ligatures are placed around the occipital artery or the external carotid artery above and below the carotid body. The pathway from the aortic chemoreceptors to the respiratory centers runs in the vagus trunk and to exclude the high vagal section is necessary. Following results are obtained. 1. There are marked individual differences in both cardiovascular and respiratory reactions against the inhalation of low % of O_2, high % of CO_2 gas mixtures which are administered in these experiments. 2. After the chemoreceptoric denervation, the results become considerably constant. 3. After the chemoreceptoric denervation of both carotid and aortic bodies the results show mostly integrativeness. 4. Before and after functional denervation of the chemoreceptors using the inhalation of 100% O_2, the action mode of aminocordine does not change essentially.
- 千葉大学の論文
- 1957-03-28