A study of lithium uptake and location in the brain using the nuclear track technique

Nuclear track technique was used to study the lithium uptake and location in the brains of rats. Male rats were injected intraperitoneally with does of 99.6% enriched 6Li carbonate in an inert carrier at a dose of 20 mEq/kg body weight. The rats were sacrificed at times ranging from zero to 48 hours after injection. The tissue sections (0.5 mm thick) were freeze-dried and sandwiched between two dyed cellulose nitrate detectors (Kodak type LR-115). The slices and CN detectors were then placed in a polyethylene envelope which was heat sealed under vacuum. The sample detector combination was then irradiated in a thermal neutron flux of 1.33x1013n.cm-2.sec-1. Irradiation times were varied from 5 to 90 seconds. Following irradiation, the CN detectors were chemically etched. The track density produced by the nuclear reaction 8Li(n,α)3H was determined with the aid of a light transmission microscope connected to an image analyzing system. This study indicated that a maximum lithium concentration was reached in the brain eight hours after an intraperitoneal injection. (T.G.)