Neonatal clonazepam exposure reprograms hippocampal molecular pathways and impairs episodic-like memory in adult rats

Benzodiazepines are frequently prescribed during early life, yet little is known about their long-term effects on hippocampal maturation and memory-related neural circuits. Here, we examined whether neonatal clonazepam (CLZ) exposure leads to persistent alterations in hippocampal molecular markers associated with neurosteroidogenesis and glutamatergic signaling, and whether these changes are accompanied by deficits in episodic-like memory (ELM). Male rats received CLZ (1 mg/kg/day) or vehicle from postnatal day (PND) 7 to 11 and were evaluated in adulthood. Neonatal CLZ exposure selectively impaired the temporal component of ELM without affecting spatial discrimination. In addition, CLZ animals displayed reduced expression of 5α-reductase type 1, and 3α-hydroxysteroid dehydrogenase in the dentate gyrus and/or CA1, consistent with a long-lasting reduction in the hippocampal neurosteroidogenic pathway. Some of these changes were associated with altered DNA methylation profiles. Moreover, CLZ exposure produced region-specific changes in NMDA receptor subunit expression, characterized by increased GluN1 mRNA levels in CA3 together with decreased GluN2A, GluN2B, and GluN3A expression in CA1. These results show that pharmacological modulation during critical periods of brain development can produce persistent alterations in hippocampal function, potentially through interactions between neurosteroid synthesis, epigenetic regulation, and glutamatergic neurotransmission.