Enhanced Novel Object Recognition and Spatial Memory in Rats Selectively Bred for High Nicotine Preference

This study examined the influence of genetic background on cognitive performance in a selectively bred high nicotine-preferring (NP) rat line. Using the novel object recognition (NOR), novel location recognition (NLR), and Morris water maze (MWM) tests, we evaluated object memory, spatial memory, and spatial navigation in nicotine-naive NP rats compared to controls. Our results demonstrate that in the NOR test, both male and female NP rats spent more time exploring the novel object (higher discrimination index) compared to sex-matched controls. In the NLR, the discrimination index differed significantly from zero chance (no preference) in both NP males and females but not in controls, indicating enhanced spatial memory in the NP line. During MWM acquisition, the NP groups and control males took a shorter path to reach the platform compared to control females. On the probe trial, the distance traveled in the target quadrant was longer for NP males and females compared to their respective controls, suggesting enhanced spatial navigation and learning in the NP rats. The interesting preference for novel objects and locations displayed by NP rats may indicate a potential novelty-seeking phenotype in this line. These results highlight the complex interplay between genetic factors, cognitive function, and nicotine preference.