Demonstration of deacetylated hippocampal cholinergic neurostimulating peptide and its precursor protein in rat tissues

This report concerns the demonstration of hippocampal cholinergic neurostimulating peptide (HCNP), its deacetylated analogue (free HCNP) and HCNP precursor protein in rat tissues. To avoid possible enzymatic degradation during sample manipulation, tissue extracts were prepared under acidic conditions using trifluoroacetic acid. The tissue contents of free HCNP and of precursor protein were determined by radioimmuno-assay (RIA) using two antibodies with different specificities, and by a combination of HPLC and RIA. Free HCNP was detected in neuronal and renal tissues, but not in liver. All tissues examined had measurable amounts of HCNP precursor protein. The concentrations of free HCNP and precursor in neuronal tissues were inversely related to the age. These results suggest that the deacetylated analogue of HCNP and its precursor protein may have significant physiological functions, especially in the central nervous system of young animals.