Cognitive and histological disturbances after chlorpyrifos exposure and chronic Aβ(1-42) infusions in Wistar rats

Exposure to pesticides has been linked to an increased vulnerability to neurodegenerative diseases. In order to study whether the exposure to the organophosphate chlorpyrifos renders the brain prone to amyloid-beta peptide deposition and accelerates its neuropathological and behavioural effects, Wistar rats were injected a single subcutaneous dose of chlorpyrifos (250 mg/kg) and subsequently infused with Aβ(1-42) peptide (i.c.v.) for 15 days. No effects of either treatment were noted in the classic water maze test. The animals infused with Aβ peptide showed worse performance when the platform was both hidden and moved from trial to trial. Both groups showed worse performance when the platform was visible and moved from trial to trial. No amyloid deposition was observed in hippocampus or cerebral cortex after the infusion period, although microtubule-associated protein 1A (MAP1A) immunoreactivity was significantly reduced in hippocampus and prefrontal cortex, whereas chlorpyrifos exposure produced a significant reduction of microtubule-associated protein 2 (MAP2) in the prefrontal cortex. Therefore, behavioural deficits could be related to a loss of dendrite and spine processes in these brain regions.