Abstract
Summary
1. SKF 525-A caused an increased tension in the isolated frog rectus abdominis muscle. After treatment with SKF 525-A the response to acetylcholine (ACh) was inhibited, and the inhibition could not be reversed by repeating washing of the muscle with fresh Ringer's solution. The inhibition differed from that observed with d-tubocurarine and atropine. 2. SKF 525-A had no direct effect in low concentrations on the isolated rabbit ileum, but it prevented spontaneous rhythmic activity in higher concentrations. It inhibited the effect of ACh on the gut and this inhibition was reversed by repeated washings with fresh Tyrode's solution. 3. SKF 525-A raised the threshold to direct electrical stimulation of the frog gastrocnemius muscle. 4. SKF 525-A inhibited the enzyme pseudocholinesterase. 5. These data are not fully explained, but the results indicate that SKF 525-A has properties which differ markedly from those previously reported concerning the inhibition of microsomal detoxifying enzymes.
We wish to express our thanks to Dr. R. E. Gosselin for the privilege of working in his laboratory. Smith, Kline, and French kindly supplied the samples of SKF 525-A.
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