TRYPTOPHAN-HYDROXYLASE CAN BE PRESENT IN MAST-CELLS AND NERVE-FIBERS OF THE RAT DURA-MATER BUT ONLY MAST-CELLS CONTAIN SEROTONIN

Tryptophan hydroxylase-immunopositive (TPH-I) but not serotonin-I nerv e fibers were observed in the rat dura mater. This tissue also contain ed numerous serotonin and TPH-I mast cells. The TPH appeared to be loc ated in granules and/or enclosed in a juxta-nuclear organite. Westernb lots showed that the TPH located in the dura mater is similar to the T PH of pineal gland but different from raphe TPH. According to the anim al, both nerve fiber and mast cell TPH immunoreactivity was highly var iable in intensity and in number of labelled elements. This variabilit y might be due to the complex regulatory mechanisms of TPH as indicate d by the presence of two types of mast cells.