Arthur B. Eisenbrey

The mechanism of the depressor action of dog's urine with some observations on the antagonistic action of adrenalin

Summary The intravenous injections of dogs urine into the dog causes an abrupt but transient lowering of blood pressure, varying from 20 to 90 mm. Hg (usually 40 to 70), not accompanied by disturbance of heart action and with little respiratory disturbance. Section of the spinal cord, vagi, cervical sympathetic and splanchnic nerves and destruction of cœliac ganglia and solar plexus individually or collectively does not abolish the depressor action. Physiological and pharmacological experiments based on Dixons studies of the action of apocodeine show that when the nerve endings are so paralyzed by apocodeine that adrenalin causes little or no reaction, the urine also has no effect. Likewise, in normal animals, and in those with central vaso-motor influence eliminated, the action of urine is antagonistic to that of adrenalin and barium and during the increased pressure due to electrical stimulation of the nerves of the splanchnic area, the urine causes a fall in pressure.

A method of isolating the cerebro-medullary circulation

In a recent study by Dr. R. M. Pearce and myself of the mechanism of certain experimental conditions of low blood pressure, the following difficulties were encountered: 1. When substances that have been shown by special experiments to exert a selective peripheral action are injected into the circulation of an intact animal, the results frequently point to some additional central action that tends to mask or to neutralize to some extent the usual peripheral action. 2. Substances that have an essentially central action may sometimes produce results to be explained only on the basis of an added peripheral influence. 3. In experiments accompanied by a condition of extreme low blood pressure it is often difficult to know whether to ascribe these final results directly to the primary assault on the central or peripheral mechanism respectively, or to the additional secondary effects produced by the cerebral anemia that is the concomitant of the lowered systemic blood pressure. It is evident, therefore, that a knowledge of the extent and importance of the part played primarily by the central and peripheral mechanisms respectively, and by the central mechanism secondarily, in the production of any given result, is necessary for the interpretation of the mode of action of the substance used.