Brain Acetylcholinesterase and a Respiratory Reflex

¹ From the Department of Physiology, Medical College of South Carolina, Charleston, South Carolina

Experiments were carried out to determine the correlation, if any, between the level of acetylcholinesterase (AChE) activity in the brain and the degree of respiratory reflex potentiation and inhibition which occurs after the administration of varied doses of an anticholinesterase, tetraethyl pyrophosphate (TEPP). After a steady state of reflex response was reached (elicited by electrical stimulation of Hering's Nerve), TEPP was injected in varying doses via a cisternal puncture, and the anesthetized dogs were killed at various stages of reflex potentiation and inhibition. Analyses of the AChE activity of representative brain areas indicated that following an initial marked potentiation, maximal at AChE values approximately 84–88% of the controls, there is a gradual but progressive decline in the potentiated respiratory reflex which parallels the fall in the AChE activities of the brain areas vitally concerned with respiration, until respiratory failure was evident when the enzyme activity was 8–11% of the control values. These experiments lend suggestive evidence that a neurohumoral component (e.g. acetylcholine) may be factor in respiratory control.