Immunocytochemical study of the dorsal and median raphe nuclei in patientswith Alzheimer's disease prospectively assessed for behavioural changes

The dorsal and median raphe nuclei were examined with immunocytochemistry t o display the 5-HT neurones in 16 cases of post-mortem-proven Alzheimer's d isease (AD) and 12 age and sex-matched controls. The AD cases had been pros pectively assessed during life for expression of behavioural changes as wel l as for cognitive decline. A significant (P<0.001) 41% reduction in densit y of dorsal raphe neurones was found along with a significant (P<0.02) 29% reduction in density of median raphe neurones in AD. There were significant ly more neurofibrillary tangles in both dorsal and median raphe nuclei in A D than in controls (P<0.001). There was no correlation between reduction in neurone density in these nuclei and behavioural change, cognitive decline, neurofibrillary tangle counts in these nuclei or plaque and tangle patholo gy in frontal and temporal cortex. It was concluded from these findings tha t the raphe nuclei are significantly affected by the pathology of AD and th at plasticity in the 5-HT system is the probable reason for the lack of cor relation of reduced 5-HT neurone density and clinical disease parameters.