The development of substance P, somatostatin and vasoactive intestinal polypeptide in sympathetic and spinal sensory ganglia of the chick embryo.

Antisera to substance P, somatostatin and vasoactive intestinal polypeptide were produced in rabbits and used to establish radioimmunoassays. The specificities and sensitivities of the assays were characterised before using them to measure the levels of these peptides in the paravertebral sympathetic ganglia and spinal sensory ganglia of embryonic chicks. The immunoreactive materials in the developing ganglia were shown to be identical with the peptides by the criterion of co-elution on reverse-phase high performance liquid chromatography. The levels of the peptides varied independently during the developmental period studied between day 8 and hatching at day 20 of incubation. Vasoactive intestinal polypeptide was first detectable on day 12 in the sympathetic ganglia and the levels increased through to hatching, at which time it first became detectable in the sensory ganglia. In contrast, substance P and somatostatin were detectable in both sensory and sympathetic ganglia throughout the period studied: the content of substance P increased up to day 18 after which time it declined, and somatostatin was present initially (day 8) at high levels before rapidly declining to a minimum at day 10 and then slowly increasing again, in parallel with the general growth of the ganglia, reflected by their protein contents. The differential changes in levels of substance P, somatostatin and vasoactive intestinal polypeptide during development indicates that different regulatory mechanisms are responsible for the ontogenesis of individual peptide phenotypes in the peripheral nervous system.