Lithium Administered to Pregnant, Lactating and Neonatal Rats: Entry into Developing Brain.

Background: Little is known about the extent of drugs administered to pregnant and lactating women entering the developing brain. Lithium is one of the most commonly prescribed drugs for bipolar disorder. Here we studied transfer of lithium given to dams, into blood, brain and cerebrospinal fluid (CSF) in embryonic, postnatal and adult rats. Methods: Lithium chloride in a clinically relevant dose (3.2mg/Kg body weight) was injected intraperitoneally into pregnant (E15-18) and lactating dams (birth-P16) or directly into postnatal pups (P0-P16). Acute treatment involved a single injection; chronic treatment involved twice daily injections for the duration of the experiment. Following terminal anaesthesia blood plasma, CSF and brains were collected. Lithium levels and brain distribution were measured using Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS). Results: Lithium was detected in blood, CSF and brain of all fetal and postnatal pups following lithium treatment of dams. Its concentration in pups’ blood was consistently below that in maternal blood (30-35%) indicating significant protection by the placenta and breast tissue. Levels of lithium in plasma fluctuated in different treatment groups but its concentration in CSF was stable at all ages, in agreement with known stable levels of endogenous ions in CSF. Only a small non-significant increase of lithium transfer into CSF occurred following application of Na + /K + ATPase inhibitor (Digoxin) in vivo , indicating that Na + /K + ATPase is at most only a minor mechanism for lithium transfer across choroid plexus cells into CSF early in development. Presumably lithium transfer across choroid plexus epithelial cell is occurring predominantly via other ion channels. Conclusions: Information obtained on the distribution of lithium in developing brain provides a basis for studying possible deleterious effects on brain development and behaviour in offspring of mothers undergoing lithium therapy.