Fredrick F. Yonkman

Effect of Certain Yohimbine Derivatives upon Arterial Strips

Summary 1. The hydrochloride salts of yohimbine derivatives (ethyl, allyl-amine, allyl, butyl, phenyl and diethylaminoethyl) in the dosage used, 1-500,000 to 1-50,000, do not seem to directly affect the arterial muscle strip whether it is in a contracted or relaxed state. 2. A predetermined, consistently constricting dose of epinephrine HC1, 1-1,000,000, or ephedrine, 1-25,000, administered after yohimbine derivatives is inhibited in its action. 3. This inhibitory action of the yohimbine radicle on epinephrine can be obviated by previously sensitizing the arterial strip to epinephrine by addition of cocaine. 4. Musculo-tropic agents such as histamine, 1-1,000,000, barium chloride, 1-1,000, and sodium nitrite, 1-1,000, are not modified in their actions by yohimbine derivatives. 5. These new yohimbine derivatives are antisympatheticomimetic agents.

Colon Activation by Intravenous Hypertonic NaCl Injection in Unanesthetized, Trained Dogs

Since Hughson and Scarff 1 first reported peristaltic augmentation of the ileum after NaCl intravenously in anesthetized cats, several investigators have confirmed the observation. 2 , 3 , 4 , 5 Regarding the response of the colon no action has been experimentally demonstrated. Thus our results seem interesting since they show that the large intestine can be activated by salt solutions of adequate hypertonicity when intravenously administered. This work was carried out in unanesthetized, trained collies, which had undergone cecostomy after the method described by Plant and Miller. 6 Rubber balloons of convenient size, under uniform water pressure were inserted into the anterior colon and registrations were recorded through a closed system 6 by means of Mendenhalls 7 modified Brodie 8 bellows. Varying amounts, 2 to 15 cc., of NaCl 5% and 20% concentration were injected intravenously and intracardially. Results. 5% NaCl only slightly (a) augments colonic tonus, (b) increases peristaltic amplitude. 5% NaCl does not alter peristaltic frequency. 5% NaCl shows little or no disturbance of frequency and amplitude of rhythmic waves. 20% NaCl definitely (a) augments colonic tonus, (b) increases peristaltic amplitude, (c) induces peristalsis, in the quiescent, atropinized colon. 20% NaCl shows little or no augmentation of frequency and amplitude of rhythmic waves. Similar amounts of normal saline fail to affect the colon. 20% NaCl, 1.0 cc. per kg., as here administered did not produce vomiting or retching movements. 5% and 20% NaCl failed to produce defecation in these particular experiments. No evident distress was ever observed in over 20 experiments. Conclusions. Reasonably small amounts of hypertonic NaCl solutions intravenously injected promote or augment activity of the colon. Since this increased activity can be induced after atropinization, NaCl, in this instance, probably affects either Auerbachs plexus or the intestinal muscularis directly.

An Inexpensive Tissue for Biological Testing

For some time we have been interested in reactions of the iris to various reagents and have observed that a strip of sphincter pupillae of the steer iris affords an excellent preparation for studying the effects of many drugs on unstriated muscle and its innervation. We suggest the adoption of this tissue for pharmacological studies because of its inexpensiveness, certainty and sensitivity of response, availability at any abattoir and its viability even after 3 to 7 hours post mortem. Precautions regarding preparation of iris strips are given elsewhere. 1 , 2 Besides demonstrating the antagonistic relaxing action of various concentrations of atropine against sphincter contraction by physos-tigmine one is able to produce opposite effects with histamine and adrenalin. To date we have been able to demonstrate sphincter relaxation with so small a dose as 1-400,000,000 and a sphincter contracture with the minute dose of 1-1,000,000,000 of histamine. We suggest the study of the iris sphincter strip as a probable tissue for biological assay as well as its adoption in pharmacological laboratory teaching.