Thermal dehydration-induced thirst in lithium-treated rats

Lithium is used as the primary treatment for bipolar disorder but has the common side effects of diuresis and thirst. In the present study, the effects of lithium on water balance responses of male Sprague–Dawley rats to thermal dehydration were examined. Rats ate either unadulterated food or food containing 2 g/kg lithium carbonate for 10 days. Then the control and lithium-treated rats were exposed to either 25 or 37.5 °C without food or water for 4 h. The rats were then allowed access to water for 3 h at 25 °C or were anesthetized and blood samples were taken. Lithium treatment caused an initial decrease in food intake, a decrease in body weight, and an increase in urine output. Heat exposure caused similar increases in evaporative water loss in control and lithium-treated rats. Heat exposure led to changes in blood indicators of body water status indicative of dehydration, whereas lithium had no effects on blood indicators of body water status. Water intake was increased by both heat exposure and by lithium treatment with the lithium-treated rats being more responsive to the thirst-inducing effects of thermal dehydration. Lithium treatment does not appear to impair water balance responses to heat exposure.