Developmental characteristics of substance P immunoreactivity within specific rabbit brainstem nuclei

Microdissected areas of the rabbit brainstem were isolated at prenatal day E28, postnatal days P3, 7, 14, 21, at 2 months and adults. Substance P immunoreactivity (SPI) was assayed by RIA and SPI was expressed relative to the protein content of the extracted brain tissues. The developmental characteristics of SPI within specific brainstem nuclei are reported. In general, SPI was highest in the NTS (nucleus tractus solitarii) at all ages. The pattern of distribution of SPI, however, was age-specific. The development of SPI within select nuclei demonstrated marked variability and showed both age- and nucleus-specificity.