Neonatal oxytocin prevents sex-specific spatial memory deficits induced by maternal separation through restoration of hippocampal synaptic plasticity in males
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Background
Stress during critical developmental periods causes lasting neurobiological alterations. Rodent models like neonatal maternal separation (NMS) induce cognitive alterations, particularly spatial memory deficits. Oxytocin (OT) system has been suggested to underlie these consequences, as it is critical for neurodevelopment. This neuropeptide also promotes maternal nurturing, prevents neuroinflammation and displays anxiolytic properties. This study hypothesized that early postnatal OT administration could prevent NMS-induced memory alterations in adult rats.
Methods
Sprague-Dawley rat pups (both sexes, n=8-12/group) underwent NMS with concomitant intraperitoneal OT injections. At adulthood, novel object recognition and object location tasks were performed. Further investigation was conducted through ex vivo electrophysiological recordings of functional plasticity at Schaffer collateral-CA1 synapses (male, n=7-12/group), alongside RT-qPCR of synaptic, GABAergic, neuro-inflammatory, and oxytocin receptor markers in dorsal CA1 (male, n=4-6/group).
Results
NMS induced male-specific spatial memory impairment without affecting recognition memory. Early OT completely prevented spatial memory deficits in NMS males. Electrophysiological recordings revealed that NMS suppressed CA1 long-term potentiation (LTP), and neonatal OT restored it. NMS induced transcript overexpression of neuro-inflammatory markers, GABAergic markers, and synaptic proteins in dorsal CA1. OT treatment normalized or reduced these mRNA expressions, consistent with restoration of CA1 synaptic function.
Conclusion
Early postnatal OT prevents NMS-induced spatial memory deficits and hippocampal LTP impairments in male rats, which is associated with normalized or reduced neuro-inflammatory and GABAergic transcript expressions. These findings establish exogenous oxytocin administration during a critical neonatal window as sufficient to prevent male-specific hippocampal dysfunction and cognitive deficits induced by early-life stress, identifying the oxytocinergic system as a promising target for early neuroprotective interventions.
