Abstract
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.
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