Abstract
The occurrence of 5-hydroxytryptamine (5-HT) in the mast cells of the rat skin has been demonstrated by many investigators using a biochemical method (1-7). However, Parratt and West (7) have reported that there is no correlation between the distribution of mast cells and the level of 5-HT in different layers of rat skin. According to them, the level of 5-HT in the abdominal epithelium is higher than that in the subcutaneous tissue which is reported to contain a larger amount of mast cells and endogenous histamine. They have concluded that most part of 5-HT in the rat skin is present outside of mast cells (6). Recently, a histochemical method for demonstrating the endogenous 5-HT in different tissues has been developed by Scandinavian investigators (8-11). The present experiment is an attempt to show the distribution of 5-HT in the morphological components of various parts of rat skin using this technique.
