Substance P-immunoreactive nerve fibres in the pars distalis of the anterior pituitary of macaques.

The anterior pituitary glands of Macaca mulatta and M. assamensis were stained with antiserum against substance P (SP). A substantial amount of SP-immunoreactive (ir) nerve fibres with numerous varicosities were found in the pars distalis of the anterior pituitary. They were located in the median part of the gland and were distributed mainly in its dorso-posterior region. The great majority of the varicosities were found to be related to the glandular tissue, although some apparently were located along the walls of the blood sinuses. In addition, many SP-ir cells, mostly large and oval, were distributed at the periphery of the gland. In areas where both SP-ir nerve fibres and cells were present, many cells were found to be in close proximity to the nerve fibres.