Lithium in pigmented eye rats: Effects of dose and time of day on drinking, body weight, retinal and blood distribution

Lithium has been implicated in chronobiology (Seggie, et al., 1982, 1983). Previous work was done in Wistar rats, an Albino species, which lack the enzyme for synthesis of eye pigment. This pigment is important in regulation of light cued rhythms. The present project extends observations to Long Evans rats, a strain which has a pigmented eye. Groups of adult male rats were fed one of three diets: (1) normal laboratory chow; (2) a low lithium diet: lab chow supplemented with 30 mM/kg lithium chloride; and (3) a high lithium diet: lab chow supplemented with 50 mM/kg lithium chloride. Adult male rats were house individually with free access to diet and water under a 12 hour light/12 hour dark schedule. After six weeks on the diets, body weight, water intake, plasma, red blood cell and retinal lithium and retinal weight were measured every 4 hours throughout the 24 hour cycle following sacrifice by rapid decapitation. Plasma lithium levels on the high diet were 0.57 +/- 0.02 mEq/l and did not evidence a diurnal rhythm. Plasma lithium levels on the low diet were 0.35 +/- 0.01 mEq/l and evidenced a small, but significant diurnal rhythm with levels lowest just before darkness and normal food intake. Red blood cell lithium levels were significantly higher than plasma levels at 0.83 +/- 0.02 and 0.52 +/- 0.02 mEq/l for the high and low diets. Low diet, but not high diet red blood cells lithium levels evidenced a significant rhythm with a pattern similar to that seen in plasma lithium levels.(ABSTRACT TRUNCATED AT 250 WORDS)