SHORT TERM FASTING AFFECTS NEONATAL RAT BRAIN MONOAMINE LEVELS † 1290

Brain contents of monoamines increase continuously after birth. Effects of short term fasting in neonates are not fully examined. We applied the microdialysis method to 5-day-old rat pup(n=15) and studied changes of the brain extracellular levels of monoamines and their metabolites before and 5 hr fasting. A microdialysis probe was implanted into the left striatum and pups were fasted by separating their dams. Blood glucose (mean±SE: 6.5±0.6 vs 3.5±0.3mM*, before and after 5hr fasting, respectively) and serum tyrosine (256±30 vs 134±9mM*) decreased, but blood 3-hydroxybutyric acid (467±78 vs 1969±102μM*) serum tryptophan (51±2 vs 101±2mM*) increased significantly(p<0.01). The concentrations of norepinephrine, dopamine and dopa-acetate remained at the baseline levels for the first one to two hours and then decreased (p<0.001). Homovanillic acid unchanged throughout the experiment. 5-HIAA gradually increased (p<0.001). These results suggest that neonatal rat brain monoamines are easily affected by a short term fasting and their levels reflect the serum precursor amino acid levels, which is different from previous reports on adult rats. Our study exemplifies that this microdialysis method is applicable to neonatal rat brains to examine their monoamine levels change under various conditions without any other manipulations.Figure