Ex vivo lumbar and post mortem ventricular cerebrospinal fluid substance P-immunoreactivity in Alzheimer's disease patients

The concentration of substance P-immunoreactivity (SPIR) in ex vivo lumbar cerebrospinal fluid (CSF) of patients with probable Alzheimer's disease (AD), non-Alzheimer dementias, neurological patients without dementia and control subjects was determined using a sensitive and specific competitive enzyme-immunoassay. There were no significant differences between AD patients and the other groups, but patients with late onset AD (>65 years) showed significantly higher levels of SPIR than patients with early onset (<65 years) and controls. In post mortem ventricular fluid, SPIR levels of all groups were lower compared with the lumbar compartment, but without significant group differences. It is concluded that CSF SPIR may not serve as a diagnostic marker for AD, but possibly could reflect immunological or neuroprotective processes modulated by substance P in late onset AD patients.