Abstract
It is well known that desensitization of smooth muscle preparations occurs by repeated exposure to a stimulating drug. This is called tachyphylaxis. This paper demonstrates the response of isolated rat tracheal muscle to 5-hydroxytryptamine (5-HT) as being diminished by repeated application in almost every instance and that 5-HT applied in the presence of stimulating drugs caused a further contraction when the preparation did not respond to 5-HT alone. For this reason interaction between 5-HT and other stimulating drugs was studied on the rat tracheal muscle after desensitization had occurred.
