Parvalbumin interneurons (PV-INs) are a subset of GABAergic inhibitory neurons that play a crucial role in regulating cortical and hippocampal circuits. Dysfunction of PV-INs is implicated in neurodevelopmental and psychiatric disorders. Maternal separation (MS) is a well-established rodent paradigm used to study adverse early-life experience and its long-term behavioral effects. MS has been shown to reduce PV-INs expression in different brain regions leading to disrupted cognitive behaviors. This research investigated the long-term effect of the MS on the volume of the PV-INs in the CA1 subregion of the hippocampus in rats.
Male rat pups were separated from their mothers for 3 hours daily from postnatal day (PND) 1 to PND 14. After weaning, the animals were maintained in a standard manner until adolescence. At adolescence, brain samples were extracted and the volume of the PV-INs in the CA1 area of the hippocampus was measured using the 3D stereological technique with nucleator method.
The results showed that the volume of the PV-INs in the CA1 subregion of the hippocampus in maternally separated rats was significantly smaller (p < 0.05) than the intact rats in adolescence.
This study showed that early life adverse experiences can have a persistent effect on the volume of PV-INs in the hippocampus into adolescence and suggests that MS may lead to a disruption of synaptic excitatory inhibitory balance and may be associated with symptoms related to autistic behaviors resulting from MS that have been reported in previous studies.