Marked variations of the relative distributions of neurotensin and neuromedin N in micropunched rat brain areas suggest differential processing of their common precursor.

Neuromedin N (NN) is a hexapeptide that shares a four amino acid identity with the C-terminus of neurotensin (NT) and exhibits NT-like effects in the central nervous system. Both peptides were recently shown to be encoded in the same precursor molecule. By means of specific and sensitive radioimmunoassays, we compared the distribution of immunoreactive NT and NN (iNT and iNN) in micropunched rat brain structures. The data revealed marked regional variations in the ratio of iNT over iNN. For instance, the ratio value was 4.5 in the posterior hypothalamus and 0.8 in the mammillary bodies. Reverse phase HPLC analysis of extracts of several brain regions showed that iNT and iNN coeluted with synthetic NT and NN, respectively. The results suggest that differential processing of the common neurotensin/neuromedin N precursor occurs in various regions of the rat brain.