Abstract
In an analysis of the cardiovascular mechanism of the cat by means of the changes in blood pressure and pulse rate taking place under the conditions of medullary anemia caused by temporary ligation of the carotid, vertebral and subclavian arteries, it was considered desirable to ascertain, if possible, the extent of the role played by the skeletal musculature in the maintenance of the high pressures which the animals show.
After a control tracing had been taken, in which the anemic rise of blood pressure was obtained, curare was administered intravenously in doses of 1 mg. per 5 cc. of Ringer's solution. This dose was repeated, if necessary, every five minutes until failure of the respiratory mechanism, after which time artificial respiration was maintained. Intravenous injection of curare is followed by a fall in blood pressure, due to peripheral vasomotor depression. This action is apparently on the ganglion cells (Langley), but Sollmann 1 states that this effect on the circulation passes off within fifteen minutes, while the skeletal muscular paralysis persists. Accordingly, further occlusion was delayed for about fifteen minutes in order that the effects of muscular paralysis alone might be studied. Occlusions of the head arteries were then made as before. While the height of the anemic rise was fair-in some cases double that of the control pressure-the duration before the final fall to spinal level and the number of occlusions obtainable were markedly less than in the normal animal. This is shown in the following table:
Another striking feature of the reaction in the curarized animal is the increased latent period after occlusion of the head arteries, before the onset of the anemic rise. Normally, this occurs within one second after occlusion; in the curarized animal, the anemic rise does not begin until ten seconds or more have elapsed.
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