Lithium Chloride

Toxic Effects of Lithium Chloride during Early Neonatal Period of Rat Development

Lithium chloride (85, 255, or 255+127 μg/kg) or dexamethasone (0.2 or 2 mg/kg) were subcu- taneously injected to 3-day-old rat pups, whose excretory system did not yet attain functional maturity. Both agents retarded the growth of rat pups and delayed the appearance of negative geotaxis. LD50 and therapeutic index of lithium chloride were 255 μg/kg and TI≤3, respectively. Thus, lithium salts even in low doses can be highly toxic for the developing organism.

Key Words: lithium; rat neonatal ontogeny; half-lethal dose; organismal development; behavior

Lithium salts, psychotropic normothymic agents, are widely used in psychiatric practice to treat the mania in adult patients [4]. Despite toxic effects of these salts [5,12,15], the literature focuses on the prom- ises of their use in perinatology as the neuroprotec- tive agents ameliorating damage in developing brain caused by hypoxia and/or toxic substances [3,6-8,13]. Actually, single injection of lithium chloride (LiCl) in doses of 85, 127, or 255 μg/kg can prevent neuro- toxic alterations in the brain of neonatal rat pups pro- voked by administration of ethanol or ketamine [3,8]. The minimum dose of LiCl producing significant therapeutic effect during acute administration is 85 μg/kg [3,6-8,13]. These data relate to the effects of lithium salts in rat pups aged 1 week or older, whose excretory system (the major target for the toxic effect of these salts [12,15]) virtually developed to the state of functional maturity [2]. Usually, neuroprotection is necessary for premature babies with immature excre- tory system [14], which can aggravate possible unfa- vorable consequences of the treatment with lithium salts [15]. However, the key parameters of lithium safety, such as therapeutic index (TI) and possible toxic side effects on the developing organism remain little studied.Here we analyze the effects of LiCl on general and neurological development as well as on survival of 3-8-day old rat pups whose excretory system can- not work with the same efficiency as in the following weeks of life [2].


The experiments were carried out on rat pups born and fed naturally by their Wistar mothers. The vi- varium conditions and all examination protocols were approved by Biomedical Ethics Committee of the Institute of Cytology and Genetics in compliance with EU Directive 2010/63/EU and Order No. 755 of USSR Ministry of Health (August 12, 1977) on protection of animals used for scientific purposes. The parturition day was considered as postnatal day 1 (PD1).

On PD3, rat pups received subcutaneous injection of 85 or 255 μg/kg LiCl dissolved in 0.9% NaCl. In a special subgroup, the pups additionally received 127 μg/kg LiCl in 24 h after the first injection of 255 μg/kg LiCl. Controls were injected with 0.9% NaCl. Toxic effects of LiCl were compared with those of a well- examined steroid medication dexamethasone (DEX) [9,11] that was injected on PD3 in doses of 0.2 and 2 mg/kg. Animal development and the formation of behavioral reactions (righting, negative geotaxis, and cliff avoidance reactions) were assessed daily in the period from 10.00 to 12.00 [10]. The duration of daily behavioral examination did not exceed 10 min for minimization of the effects of stress.

Significance of the effects of both agents on body weight gain (BWG) and behavior was assessed using two-factor ANOVA. The intergroup differences were analyzed using the post-hoc Fisher test. The effect of the agents on animal survival was evaluated using the Mantel–Cox test.


Both LiCl and DEX produced similar effects on vis- ible behavioral markers of neurotoxicity. However, they exerted no significant effect on the formation of righting response (stimulus F(2,26)=0.27, p>0.762; age F(4,104)=21.69, p<0.00001; stimulus×age F(8,104)=0.36, p>0.938) and on the development of cliff avoidance 4). In contrast, DEX even in the high dose did not cause animal death.

Fig. 1. Effect of single injection of LiCl or DEX on the formation of negative geotaxis. 1) Saline; 2) 85 μg/kg LiCl; 3) 0.2 mg/kg DEX.

The dynamics of BWG and survival of experi- mental animals suggests that the nature of BWG delay is different for the examined agents. The effect of DEX on BWG is related to the well-known cata- bolic action of this drug on metabolism in newborn animals [9,10]. In contrast, LiCl produces a non-spe- cific delay of general development, which is similar to the effects produced by salts of the alkali metals [5]. The data showed that LD50 of LiCl administered by a single injection to 3-day old rat pups was 255 μg/kg. It is important that the far greater doses of LiCl did not lead to the death of rat pups older than 1 week [3,6-8,13]. High sensitivity to lithium salts in animals at this developmental stage characterized by functional immaturity of the excretory system [2] can be of practical value since intensive therapy (neuroprotection included) is mostly used for pre- term neonates with functionally immature excretory system [14].

It has been previously demonstrated that the me- dian effective dose of single LiCl injection that pro- duces a significant therapeutic effect in 50% animals of LiCl as a neuroprotective drug used in the early neonatal period is merely 3. This extremely low TI can be nevertheless sufficient in experimental stud- ies on perinatal animals focused on the molecular basis of neuroprotection of individual cell popula- tions and on the development of novel neurotropic preparations. However, very low TI of lithium salts attests to their dangerous role in perinatal neuropro- tection.