CENTRAL RESPIRATORY DEPRESSANT ACTION OF "HEMICHOLINIUM" IN THE CAT

¹ Department of Pharmacology, University of Utah College of Medicine, Salt Lake City

The depressant effects of "hemicholinium" No. 3 (HC-3) on the respiration were analyzed by means of electrical stimulation and transections of the lower brain stem in unanesthetized, pentobarbitalized, and decerebrate cats, with and without vagotomy. The effects on blood pressure were also investigated simultaneously. The conclusions are as follows:

The respiratory parabyzant action of HC-3 is due mainly to depression of the regulatory mechanisms in the brain stem rather than to depression of the spinal cord.

This brain stem depression involves three functions of respiration in the following order—modulator, oscillator, and integrator.

HC-3 does not depress pacemaker function; hence, cough responses can he elicited after respiratory cessation.

Large doses of HC-3 produce neuromuscular blockade which synergizes with the central respiratory paralyzant effect of HC-3. However, central depression takes precedence over peripheral neuromuscular blockade.

The central depressant effect is manifested on medullary vasomnotor regulation as well as on respiration, after doses of HC-3 too small to cause ganglionic blockade.