Respiratory changes after intraarterial acetylcholine and abdominal concussion.

ABSTRACT

In 50 dogs anesthetized with chloralose the respiratory changes produced by intraarterial acetylcholine (ACh) and after an abdominal blow, were studied. Intraarterial ACh produced expiratory apnea when it was injected in the superior and inferior mesenteric artery, splenic and left gastric artery. This apnea disappeared when the splanchnic nerves were severed and disappeared or decreased after atropine sulfate was injected. The duration of the apnea coincides with the contraction of the gut smooth muscle recorded, with a small balloon placed in the jejunum or in the ileum. The ACh did not produce respiratory changes when it was injected in the hepatic artery and pulmonary trunk. In the peripheral arteries, especially in the subclavian, ACh injection produced a respiratory stimulation which could be caused by the pain which accompanied the muscular contraction. After a blow in the abdominal wall, an expiratory apnea was also obtained, similar to that observed by the injection of ACh in the gastrointestinal arteries. This apnea disappeared when splanchnic nerves were severed or when atropine sulfate was injected. Smooth muscle contraction was also observed, suggesting that the expiratory apnea was originated in the smooth muscle receptors.