ABSTRACT
In our previous studies, substance P-like immunoreactive varicose nerve fibers have been demonstrated in the pars distalis of the adenohypophysis of the dog. They were found, at light microscopical level, to be closely related to gland cells. In the present study, the ultrastructure of substance P-like immunoreactive nerve fibers and their relationship with the gland cells of the pars distalis in the dog were investigated by use of pre-embedding immuno-electron microscopy. Direct contacts could be ascertained on every cell type of the gland, including folliculo-stellate cells. Typical synapses were identified on somatotropes and corticotropes, more on the latter. Most of them were of asymmetrical type with round to oval small clear vesicles and scattered large dense cored vesicles. It is considered morphologically proved that the substance P-like immunoreactive nerve fibers have effector role in the pars distalis of the dog.