Spatial memory impairment in OLETF rats without cholecystokinin – a receptor

Cholecystokinin (CCK) is one of the most abundant neurotransmitter peptides in the brain. As Otsuka Long-Evans Tokushima Fatty (OLETF) rats lack CCK-A receptor because of a genetic abnormality, we examined whether learning and memory were impaired in these animals using both Morris water maze (MWM) and step-through type passive avoidance (PA) learning test. In the MWM test, memory impairment was observed in OLETF rats. The number of errors was also significantly higher, and that of the correct choices was significantly lower in OLETF rats compared to the controls [Long-Evans Tokushima Otsuka (LETO)] rats. In PA, OLETF rats did not show facilitating response 24 h after training. From these observations, we concluded that a spatial memory was impaired in the OLETF rats.