Vasoactive intestinal polypeptide carboxy-terminal fragment, VIP(22–28), and other fragments of VIP, in the central nervous system of the rat

The possible existence in rat brain tissues of shorter peptides related to VIP has been examined. VIP and PHI both contain paired basic amino acid residues at which posttranslational cleavage of these peptides might occur. Antiserum to VIP(22–28) was raised in rabbits. The antiserum was carboxy-terminus directed, showing cross-reactivity with all tested peptides containing the VIP carboxy-terminus sequences. Chromatographic analysis of rat brain extracts demonstrated that recovered VIP(22–28) immunoreactivity [VIP(22–28)-ir] was heterogeneous, consisting of a major fraction [60–70% of total VIP(22–28)-ir] which eluted as authentic VIP(1–28) on gel filtration and on reversed phase high performance liquid chromatography (HPLC) columns. A second fraction (30–35% of total VIP(22–28)-ir] eluted from gel filtration columns in the position of VIP(22–28). HPLC analysis of this fraction from extracts of rat cortex, hippocampus, and midbrain indicated that it was heterogeneous. One component corresponded to authentic VIP(22–28). The other two components have not been identified; one appears to be a VIP fragment intermediate in size between VIP(1–28) and VIP(22–28).