Acute administration of lithium carbonate interferes with suckling in neonatal rats.

These studies provide an animal model for the lithium-induced decrease in suckling reported in the clinical literature that allows for more precise determination of causal mechanisms. Nine-day-old rat pups were administered lithium carbonate via either intraperitoneal (IP) injections or intragastric (IG) gavage in doses approximating that which human infants might receive via breast milk. The pups were tested for their ability to locate and attach to the nipples of an anesthetized dam. Lithium significantly increased the pups' latency to attach to a nipple. Further tests of milk extraction using oxytocin-induced milk-letdowns indicate that lithium also interferes with milk withdrawal. Tests of motor and sensory deficits using an open-field and an olfactory choice test indicated that lithium did not similarly impair these behavioral facets of suckling. Alternative mechanisms for lithium-produced suppression of suckling are discussed.