The relationship of substance P-immunoreactive nerve fibers to thyrotropes and corticotropes in the pars distalis of the anterior pituitary in the monkey.

In our previous studies substance P-immunoreactive nerve fibers have been demonstrated in the pars distalis of the anterior pituitary in macaque monkeys, and they have been found to contact somatotropes. The present study investigated the relationship of the substance P-immunoreactive fibers to thyrotropes and corticotropes. Macaca mulatta monkeys were used. Sections of the anterior pituitaries were double immunostained with antisera against either substance P and human thyrotropin or substance P and human adrenocorticotropic hormone. Substance P-immunoreactive varicosities were found to be in close proximity to thyrotropes and corticotropes. It is therefore suggested that a direct neural factor may take part in the regulation of thyrotropin and adrenocorticotropic hormone secretion.