Co-distribution patterns of chromogranin B-like immunoreactivity with chromogranin A and secretoneurin within the human brainstem.

As members of the chromogranin family, chromogranin A, chromogranin B, and secretogranin II are acidic proteins found in large, dense core vesicles. They are endoproteolytically processed to smaller peptides and released after neuronal stimulation. Using immunocytochemistry, this study closely examines chromogranin B-like immunoreactivity within the human brainstem and then takes a comparative view of co-distribution patterns by chromogranin B, chromogranin A, and secretogranin II. We used an antiserum raised against a synthetic peptide (PE-11) present in the chromogranin B molecule. Secretogranin II was localized with an antiserum against secretoneurin, a 33 amino acid peptide, found within the secretogranin II precursor. Like chromogranin A and secretoneurin, chromogranin B is expressed through all levels of the human brainstem. Chromogranin B was exclusively detected in neuronal structures. The medial part of the substantia nigra pars reticulata, the nucleus interpeduncularis, the area of the central gray, and the raphe complex displayed a high density of PE-11-like immunoreactivity. Furthermore, a prominent staining was found in the medial, dorsal and gelatinous subnuclei of the solitary tract and the dorsal motor nucleus of vagus. The substantia gelatinosa of the caudal trigeminal nucleus and spinal cord were also very strongly PE-11-immunopositive. In conclusion, chromogranin B and secretogranin II showed similar distributions while neuronal localization typically differed from chromogranin A aside from a few exceptions. These findings may provide a framework for future research in revealing a functional role of chromogranin peptides in the human brainstem.