Early Life Drug Exposure: Lasting Brain and Behavior Changes in Rodents

The central nervous system (CNS) undergoes critical development during early postnatal life, a period of heightened plasticity. Exposure to pharmacological agents during this sensitive window can profoundly alter brain maturation and function. This comprehensive review synthesizes existing experimental data to understand how neonatal drug injections lead to remote, genotype-dependent changes in adult physiological and behavioral responses in mice and rats.

The review demonstrated that neonatal injections of various pharmacological agents consistently led to detectable, long-term alterations in adult animals. These changes manifested across diverse domains, including audiogenic seizure proneness, anxiety-fear, exploratory behavior, and pain sensitivity. Notably, the observed remote effects were often genotype-dependent, meaning the outcome varied significantly based on the genetic background of the mice or rats studied. > The most significant finding was that these early life pharmacological interventions could induce lasting changes in CNS development, potentially altering neurotransmitter system development and even leading to morphological deviations such as altered neuron numbers and adult neurogenesis. The direction of these remote effects was complex, sometimes mirroring the acute effects of the drug in adults, but at other times producing entirely opposite outcomes, highlighting the unique developmental plasticity of the neonatal brain.