Plasma lithium as a marker of lithium chloride in wild Norway rats (R. norvegicus)

A parametric study was conducted to determine the efficacy of plasma lithium as a marker of lithium chloride ingestion and dose in conditioned taste aversion research with rats. Separate groups of male wild Norway rats were given 60, 120 and 240 mg/kg doses of a lithium chloride solution by gavage. At 0.5, 1, 2, 24, 48 and 72 hr after dosing, 2-3 cc samples of blood were taken from each rat: these were centrifuged and 0.5-1.0 cc specimens of plasma were frozen for later analysis. Flameless atomic absorption spectroscopy was then used to determine quantities (ppm) of lithium in these specimens. Analyses of the data revealed that plasma lithium was both dose and time dependent; however, uptake and elimination of the lithium was rapid (less than or equal to 48 hr for 60 and 120 mg/kg-dosed rats). Results showed that measurements of plasma lithium has some utility as a marker of lithium chloride ingestion in laboratory studies, but limited potential in field studies, of conditioned taste aversion with rats.