Voluntary lithium intake, antidotal thirst' and concurrent behavior of rats.

1 Voluntary intake of various pair combinations of fluids (100 mM, 10 mM LiC1, 10 mM NaC1, water) and body weight was measured daily in rats. 2 More lithium was consumed when water was available. 3 When offered a lithium-sodium choice the rats did not consume significantly more saline than water on the previous trial. While saline consumption increased over the two days, lithium decreased slightly. 4 Following the lithium-only trial, water and saline were provided. Marked polydipsia was observed on the first day and the rats drank more water than saline. On the second day there was a significant drop in saline intake while water consumption returned to baseline levels. 5 Behavioural measurements overall confirmed the depressant effect of lithium: decreased ambulation and rearing and increased time spent immobile/grooming. 6 These findings are discussed with reference to lithium toxicity, which may be a comfounding variable in studies concerned with the effects of this salt on the behavior of laboratory rodents. Behavioural irritability such as aggression reported in situations using long-term lithium treatment may be reduced by provision for voluntary saline consumption.