SENILE PLAQUES STIMULATE MICROGLIA TO RELEASE A NEUROTOXIN FOUND IN ALZHEIMER BRAIN

Senile plaques found in the brains of patients with Alzheimer's diseas e (AD) are surrounded by clusters of reactive microglia. Isolated huma n microglia placed in contact with plaques in vitro are activated to r elease a factor which is toxic to neurons. This same neurotoxin is fou nd in AD brain tissue and causes damage to pyramidal neurons in vivo w hen infused into rat hippocampus. Highest concentrations of the neurot oxin are in those brain structures most burdened by reactive microglia , suggesting that plaque-activated cells contribute to the neuronal da mage and impaired cognition seen in patients with Alzheimer's dementia .