Distribution of chromogranin B-like immunoreactivity in the human hippocampus and its changes in Alzheimer's disease

Synapse loss is crucially involved in cognitive decline in Alzheimer's dise ase (AD). This study was performed to investigate the distribution and dens ity of chromogranin B-like immunoreactivity in the hippocampus of control c ompared to AD brain. Chromogranin B is a large precursor molecule found in large dense-core vesicles. For immunocytochemistry we used an antiserum rai sed against a synthetic peptide (PE-11) present in the chromogranin B molec ule. Chromogranin B-like immunoreactivity was concentrated in the terminal field of mossy fibers, the inner molecular layer of the dentate gyrus and i n layer II of the entorhinal cortex. In AD, chromogranin B was detected in neuritic plaques. The density of chromogranin B-like immunoreactivity was s ignificantly reduced in the inner molecular layer of the dentate gyrus and in layers II, III and V of the entorhinal cortex in AD brains. The present study demonstrates that chromogranin B is a marker for human hippocampal pa thways. It is particularly suitable for studying nerve fibers terminating a t the inner molecular layer of the dentate gyrus. It is present in neuritic plaques, and its density is reduced in a layer-specific manner.