Prodynorphin peptide distribution in the forebrain of the syrian hamster and rat: A comparative study with antisera against dynorphin A, dynorphin B, and the C‐terminus of the prodynorphin precursor molecule

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Abstract
The neuroanatomical distribution of the prodynorphin precursor molecule in the forebrain of the male Syrian hamster (Mesocricetus auratus) has been studied with a novel antiserum directed against the C‐terminus of the leumorphin [dynorphin B (1–29)] peptide product. C‐peptide staining in sections from colchicine‐treated hamsters is compared to staining in sections from untreated animals. In addition, the pattern of C‐peptide immunostaining in hamster brain is compared to that in the rat brain. Finally, the C‐peptide immunolabeling patterns in hamsters and rats are compared to those obtained with antisera to dynorphin A (1–17) and dynorphin B (1–13). Areas of heaviest prodynorphin immunoreactivity in the hamster include the hippocampal formation, lateral septum, bed nucleus of the stria terminalis, medial preoptic area, medial and central amygdaloid nuclei, ventral pallidum, substantia nigra, and numerous hypothalamic nuclei. Although this C‐peptide staining pattern is similar to dynorphin staining reported previously in the rat, several species differences are apparent. Whereas moderate dentate gyrus granule cell staining and no CA4 cell staining have been reported in the rat hippocampal formation, intense immunostaining in the dentate gyrus and CA4 cell labeling are observed in the hamster. In addition, the medial preoptic area, bed nucleus of the stria terminalis, and medial nucleus of the amygdala stain lightly for prodynorphin‐containing fibers and cells in the rat, compared to heavy cell and fiber staining in the hamster in all three of these regions. In the rat there is no differential staining between tissues processed with the C‐peptide, dynorphin A, and dynorphin B antisera, but numerous areas of the hamster brain show striking differences. In most hamster brain areas containing prodynorphin peptides, the C‐peptide antiserum immunolabels more cells and fibers than the dynorphin B antiserum, which in turn labels more cells and fibers than dynorphin A antiserum. However, exceptions to this hierarchy of staining intensity are found in the lateral hypothalamus, substantia nigra, arcuate nucleus, and habenula. The differences in staining patterns between rat and hamster are greatest when C‐peptide antiserum is used; apparent species differences are present, though less pronounced, in dynorphin B– and dynorphin A–immunostained material.