Immunochemical evidence of cholecystokinin-like peptides in brain

Abstract

A NUMBER of peptides including substance P^1,2 somatostatin³ and vasoactive intestinal peptide⁴, have been found both in nerve cells of the brain and gut and in gastrointestinal endocrine-like cells. The biological significance of the occurrence of the same peptides in endocrine and nerve cells is not yet clear, although Pearse has suggested that these cell types might share a common embryological (neuroectodermal) origin⁵. An antibody to the antral hormone gasrin has recently been shown to cross react with material in extracts of the central nervous system (particularly cerebral hemispheres) of a number of vertebrate species including dog and man⁶. It is known that in antral mucosa, and in blood, gastrin occurs in several different forms of which the most important are peptides of 17 (G17) and 34 (G34) amino acid residues⁷. The C-terminal hepta-decapeptide of G34 is identical with G17, and G34 may well be a biosynthetic precursor of G17 (ref. 7). The C-terminal pentapeptide of the two gastrins is also identical with that of the intestinal hormone cholecystokinin (CCK)⁸, and antibodies specific for the C terminus of gastrin frequently cross react with CCK⁹. The present study was undertaken to clarify the relationships between the gastrin-like activity in brain and the characteristic forms of gastrin and CCK. We found the distribution of the brain components on Sephadex G-25 to differ from those of previously characterised forms of gastrin and CCK. The pattern of reactivity with different antisera suggests, however, that the brain factors resembled CCK-like peptides more closely than gastrin-like peptides.