Effects of prenatal choline supplementation on behavioral and neural reactions to social isolation rearing in the rat
Document Type Dissertation/Thesis
Choline is a crucial nutrient that contributes to several biological functions and serves as a precursor molecule to the neurotransmitter acetylcholine. Choline is integral to the development and function of the central nervous system, and its availability during the prenatal period has lasting and protective effects on neural function. Researchers have found that prenatal choline supplementation in the rat enhances learning and memory processes later in life, especially those involving spatial memory. Researchers have also demonstrated that choline protects against a number of physical stressors to the neural environment, such as prenatal alcohol exposure, induced seizures, and chronic stress-induced exposure to corticosteroids. Compared to the study of these types of physical stressors, relatively little research has examined the influence of prenatal choline exposure on psychological stress later in life. In an attempt to contribute to this field, the present study examined the effects of prenatal choline supplementation on behavioral and neural reactions to social isolation rearing, which typically produces a number of behavioral and cognitive deficits in the rat. Rats were exposed to either a choline-sufficient (CON) or a choline-supplemented (SUP) diet during prenatal development (ED 10-22), and were then weaned into standard pair-housing (PH) or social isolation (SI). When these rats reached adulthood (PD 60), behavioral measures of anxiety, exploration, object and place recognition memory, and spatial reference and working memory ability were taken. To investigate the neural basis for behavioral effects, levels of hippocampal adult neurogenesis were measured. In analyzing behavioral measures we found some consistent effects of prenatal choline supplementation. SUP rats demonstrated superior abilities in object and place recognition memory, and spatial reference and working memory, but were not less anxious than CON rats. Neural measures also revealed higher levels of adult neurogenesis in some groups of SUP rats. However, our failure to detect consistent effects of housing in CON rats prevents us from drawing any conclusions about the potential for prenatal choline supplementation to protect against the psychological stress of social isolation. Even so, these novel findings suggest that the benefits of prenatal choline supplementation may be contingent upon experiences such as social rearing, and that choline supplementation may impact an animal's sensitivity to environmental conditions.