MAPPING OF LITHIUM IN THE BRAIN AND VARIOUS ORGANS OF THE MOUSE EMBRYO

Using the ''Neutron Capture Radiography'' method, we have studied the distribution of lithium in embryos of mice subjected to chronic or acu te lithium treatments. In this method, the Li-6 isotope of lithium con tained in histological sections of the embryos is subjected to a nucle ar reaction induced by slow neutrons, which splits the Li-6 nucleus in to two ionising particles, alpha and H-3. The interaction of these ion ising particles with an appropriate detecting film creates tracks in t he detector which map the distribution of Li-6 in the histological pre parations. From the 10(th) to the 19(th) day of pregnancy, the lithium image in the various parts of the embryo tend to decrease in intensit y, with a minimum close to the 16(th) day, then it increases again. Th is time course of lithium accumulation in the embryos parallels rather well that of the lithium concentration in the mothers' blood. In the embryos, the lithium image is especially intense in the bones, the hea rt, the eyes and some endocrine glands (hypophysis, thyroid), while ti ssues of endodermaal origin, such as the liver, the stomach and the lu ngs, are significantly less strongly labelled. The distribution of lit hium in the nervous tissues of the embryos is almost homogeneous, in c ontrast with regionalisation which is known to exist in the brain of t he adults.