Distribution of substance P-like immunoreactivity in the lower brainstem of the human fetus: an immunohistochemical study.

The regional distribution of substance P-like immunoreactive (SPI) structures in the lower brainstem of the human fetus was investigated using the indirect immunofluorescence technique. SPI cells were found in a number of areas including the inferior colliculus, central gray matter of the midbrain, n. laterodorsalis tegmenti, midbrain and medullary reticular formation, n. vestibularis inferior, and n. prepositus hypoglossi. An extensive network of SPI fibers of varying densities were identified throughout the lower brainstem.