In vivo synthesis of substance P in the corpus striatum of the rat and its transport to the substantia nigra

Incorporation of ³⁵S]methionine into substance P in the striatum of the rat and the subsequent transport of the labelled peptide to the substantia nigra has been demonstrated in vivo. After a 4-h infusion of ³⁵S]methionine into the corpus striatum and an additional interval of 4 h radiolabelled substance P was found in the striatum and the substantia nigra of the animals. The criteria for concluding that the labelled product was substance P were: (a) gel chromatography and subsequent ion exchange chromatography of an acetic acid extract of the infused striatum or the ipsilateral substantia nigra yielded a peak of radioactivity co-eluting with endogenous immunoreactive substance P or a sample of synthetic substance P; (b) the radioactive material from this peak also co-chromatographed with synthetic substance P on high-voltage paper electrophoresis or high-pressure liquid chromatography; and (c) bound specifically to the substance P antibody. Intracisternal injection of colchicine (70 μg, i.c.) completely suppressed the appearance of radiolabelled substance P immunoreactive material in the substantia nigra.The data indicate that synthesis of substance P occurs in nerve cell bodies located in the corpus striatum and that substance P is transported to the substantia nigra by a colchicine sensitive mechanism.