S. H. Ngai

EFFECTS OF ANESTHETICS ON NEUROMUSCULAR TRANSMISSION AND SOMATIC REFLEXES.

Effects of various anesthetics on neuromuscular transmission and somatic reflexes were studied in unanesthetized, midcollicular decerebrate and spinal cats respectively. Diethyl ether was the only agent which significantly decreased the tibialis twitch response to indirect stimulation but an inspired concentration much higher than that required to produce areflexia was necessary. Cyclopropane, and to a lesser extent nitrous oxide and chloroform, increased the tibialis twitch response. It appears that, at least with cyclopropane, this response is a postsynaptic phenomenon distinct from its depressant action on the nervous system. All of the potent anesthetics tested, with the exception of methoxyflurane, abolished spinal (poly-synaptic) and cephalic reflexes simultaneously. Methoxyflurane depressed the spinal reflex earlier and at a lower inspired concentration.

RESPIRATION COORDINATING MECHANISM OF THE BRAIN STEM—A FEW CONTROVERSIAL POINTS*

FIQIJRE 1. Respiratory responses on electrical stimulation of the pons and medulla in the cat. Spirogram, inspiration downward. Parameters of stimulating currents : intensity 5 volts; pulse duration, 2 milliseconds; frequency, cycles per second, 1, 5; 2,25; 3,50; 4,100; 5,200. B. Inspiratory response in the middle and caudal pons. C. Expiratory apnea in the pons. D. Expiratory apnea and active expiration in the rostral medulla. E. Inspiratory response in the medulla. F. Active expiratory response in the medulla oblongata caudad to the obex.

Pharmacologic and Physiologic Aspects of Anesthesiology

DURING the six years since our last report of progress in the field of anesthesiology1 there have been important advances in the acquisition of scientific information and in the application of this...

EFFECTS OF 2‐AMINO‐2‐HYDROXYMETHYL‐1,3‐PROPANEDIOL ON THE CENTRAL RESPIRATORY MECHANISMS IN THE CAT*

The effect of 2-amino-2-hydroxymethyl-1 3-propanediol, an organic buffer often called Tris buffer or THAM, on respiratory movements was studied in decerebrate cats with brain stem transection a t various levels. The respiratory responses to electrical stimulation of the pontile pneumotaxic center, the medullary inspiratory center, and to stimulation of the central cut end of the vagus nerve before and during the infusion of the amine buffer were also investigated. These effects were correlated with changes in arterial blood pH, carbon dioxide tension, and bicarbonate concentration, in an attempt to appraise the role of H-ions and/or carbon dioxide in the control of respiration.