Excitatory and inhibitory neuron imbalance in the intrauterine growth restricted fetal guinea pig brain: Relevance to the developmental origins of schizophrenia and autism.

Researchers studied how poor growth in the womb affects brain development using guinea pig models. They found that babies with restricted growth had fewer inhibitory brain cells (which help calm brain activity) in key brain areas, while excitatory cells (which stimulate brain activity) were normal. This imbalance might help explain why children who were small at birth have higher rates of autism and other developmental conditions.

This preclinical study investigated how intrauterine growth restriction (IUGR) affects brain development in guinea pig fetuses, specifically examining excitatory and inhibitory neurons. Researchers induced chronic placental insufficiency to create IUGR conditions and compared brain tissue from IUGR fetuses (n=8) with controls (n=7) at late gestation. The study found reduced density of somatostatin-positive inhibitory neurons in the cerebral cortex and hippocampus of IUGR fetuses, while excitatory neuron populations remained unchanged. This suggests IUGR may create an excitatory/inhibitory imbalance in the developing brain, potentially contributing to neurodevelopmental disorders like autism and schizophrenia.

Provides preliminary evidence that intrauterine growth restriction may contribute to excitatory/inhibitory imbalance associated with neurodevelopmental disorders. However, these are early-stage animal findings requiring validation in human studies before clinical application.

Very small sample size (n=2 for initial visualization, n=8 IUGR, n=7 controls). Animal model findings may not directly translate to humans. Study examined only specific time points in development. Limited to morphological analysis without functional assessment.

Neurodevelopmental disorders such as schizophrenia and autism are thought to involve an imbalance of excitatory and inhibitory signaling in the brain. Intrauterine growth restriction (IUGR) is a risk factor for these disorders, with IUGR onset occurring during critical periods of neurodevelopment. The aim of this study was to determine the impact of IUGR on excitatory and inhibitory neurons of the fetal neocortex and hippocampus. Fetal brains (n = 2) were first collected from an unoperated pregnant guinea pig at mid-gestation (32 days of gestation [dg]; term ∼67 dg) to visualize excitatory (Ctip2) and inhibitory (calretinin [CR] and somatostatin [SST]) neurons via immunohistochemistry.

Chronic placental insufficiency (CPI) was then induced via radial artery ablation at 30 dg in another cohort of pregnant guinea pigs (n = 8) to generate IUGR fetuses (52 dg; n = 8); control fetuses (52 dg; n = 7) were from sham surgeries with no radial artery ablation. At 32 dg, Ctip2- and CR-immunoreactive (IR) cells had populated the cerebral cortex, whereas SST-IR cells had not, suggesting these neurons were yet to complete migration. At 52 dg, in IUGR versus control fetuses, there was a reduction in SST-IR cell density in the cerebral cortex (p = .0175) and hilus of the dentate gyrus (p = .0035) but not the striatum (p > .05). There was no difference between groups in the density of Ctip2-IR (cortex) or CR-IR (cortex, hippocampus) neurons (p > 0.05).

Thus, we propose that an imbalance in inhibitory (SST-IR) and excitatory (Ctip2-IR) neurons in the IUGR fetal guinea pig brain could lead to excitatory/inhibitory dysfunction commonly seen in neurodevelopmental disorders such as autism and schizophrenia.