CHOLINE AVAILABILITY MODULATES THE EXPRESSION OF TGF-BETA-1 AND CYTOSKELETAL PROTEINS IN THE HIPPOCAMPUS OF DEVELOPING RAT-BRAIN

Choline availability influences long-term memory in concert with chang es in the spatial organization and morphology of septal neurons, howev er little is known concerning the effects of choline on the hippocampu s, a region of the brain also important for memory performance. Pregna nt rats on gestational day 12 were fed a choline control (CT), choline supplemented (CS), or choline deficient (CD) diet for 6 days and feta l brain slices were prepared on embryonic day 18 (E18). The hippocampu s in these brain slices was studied for the immunohistochemical locali zation of the growth-related proteins transforming growth factor beta type 1 (TGF beta 1) and GAP43, the cytoskeletal proteins vimentin and microtubule associated protein type 1 (MAP1), and the neuronal cell ma rker neuron specific enolase (NSE). In control hippocampus, there was weak expression of TGF beta 1 and vimentin proteins, but moderately in tense expression of MAP1 protein. These proteins were not homogeneousl y distributed, but were preferentially localized to cells with large c ell bodies located in the central (approximate to CA1-CA3) region of t he hippocampus, and to the filamentous processes of small cells in the fimbria region. Feeding a choline-supplemented diet decreased, wherea s a choline-deficient diet increased the intensity of immunohistochemi cal labeling for these proteins in E18 hippocampus. GAP43 and NSE were localized to peripheral nervous tissue but not hippocampus, indicatin g that the maturation of axons and neurite outgrowth in embryonic hipp ocampus were unaffected by the availability of choline in the diet. Th ese data suggest that the availability of choline affects the differen tiation of specific regions of developing hippocampus.