Substance P-like immunoreactivity is reduced in Alzheimer's disease cerebral cortex.

Substance P is an undecapeptide which has been found in human cortical neurons. We measured concentrations of this peptide in Alzheimer's disease (AD) and control postmortem tissue by radioimmunoassay. Using high-performance liquid chromatography, most of the immunoreactivity from AD or control temporal cortex comigrated with synthetic standards. Significant reductions of 20 to 40% in substance P-like immunoreactivity were found in AD cerebral cortex and hippocampus, most severe in the inferior temporal gyrus. Substance P neurons or their terminals are vulnerable to the pathophysiologic process in AD.