Neonatal seizures are associated with redistribution and loss of GABAA α-subunits in the hypoxic-ischaemic pig

GABAergic system and chloride cotransporters as potential therapeutic targets to mitigate cell death in ischemia

Gamma aminobutyric acid (GABA) is a critical inhibitory neurotransmitter in the central nervous system that plays a vital role in modulating neuronal excitability. Dysregulation of GABAergic signaling, particularly involving the cotransporters NKCC1 and KCC2, has been implicated in various pathologies, including epilepsy, schizophrenia, autism spectrum disorder, Down syndrome, and ischemia. NKCC1 facilitates chloride influx, whereas KCC2 mediates chloride efflux via potassium gradient. Altered expression and function of these cotransporters have been associated with excitotoxicity, inflammation, and cellular death in ischemic events characterized by reduced cerebral blood flow, leading to compromised tissue metabolism and subsequent cell death. NKCC1 inhibition has emerged as a potential therapeutic approach to attenuate intracellular chloride accumulation and mitigate neuronal damage during ischemic events. Similarly, targeting KCC2, which regulates chloride efflux, holds promise for improving outcomes and reducing neuronal damage under ischemic conditions. This review emphasizes the critical roles of GABA, NKCC1, and KCC2 in ischemic pathologies and their potential as therapeutic targets. Inhibiting or modulating the activity of these cotransporters represents a promising strategy for reducing neuronal damage, preventing excitotoxicity, and improving neurological outcomes following ischemic events. Furthermore, exploring the interactions between natural compounds and NKCC1/KCC2 provides additional avenues for potential therapeutic interventions for ischemic injury.

Relationship of Neonatal Seizure Burden Before Treatment and Response to Initial Antiseizure Medication

OBJECTIVE

To assess among a cohort of neonates with hypoxic-ischemic encephalopathy (HIE) the association of pretreatment maximal hourly seizure burden and total seizure duration with successful response to initial antiseizure medication (ASM).

STUDY DESIGN

This was a retrospective review of data collected from infants enrolled in the HEAL Trial (NCT02811263) between January 25, 2017, and October 9, 2019. We evaluated a cohort of neonates born at ≥36 weeks of gestation with moderate-to-severe HIE who underwent continuous electroencephalogram monitoring and had acute symptomatic seizures. Poisson regression analyzed associations between (1) pretreatment maximal hourly seizure burden, (2) pretreatment total seizure duration, (3) time from first seizure to initial ASM, and (4) successful response to initial ASM.

RESULTS

Among 39 neonates meeting inclusion criteria, greater pretreatment maximal hourly seizure burden was associated with lower chance of successful response to initial ASM (adjusted relative risk for each 5-minute increase in seizure burden 0.83, 95% CI 0.69-0.99). There was no association between pretreatment total seizure duration and chance of successful response. Shorter time-to-treatment was paradoxically associated with lower chance of successful response to treatment, although this difference was small in magnitude (relative risk 1.007, 95% CI 1.003-1.010).

CONCLUSIONS

Maximal seizure burden may be more important than other, more commonly used measures in predicting response to acute seizure treatments.

Maternal diabetes decreases the expression of GABAAα1, GABAB1, and mGlu2 receptors in the visual cortex of male rat neonates

AIMS

This study examines the impact of maternal diabetes on the expression of GABAB1, GABAAα1, and mGlu2 receptors in the primary visual cortex layers of male rat newborns.

MAIN METHODS

In diabetic group (Dia), diabetes was induced in adult female rats using an intraperitoneal dose of Streptozotocin (STZ) 65 (mg/kg). Diabetes was managed by daily subcutaneous injection of NPH insulin in insulin-treated diabetic group (Ins). Control group (Con) received normal saline intraperitoneally rather than STZ. Male offspring born to each group of female rats were euthanized via CO2 inhalation at P0, P7, and P14 days after delivery and the expression of GABAB1, GABAAα1, and mGlu2 receptors in their primary visual cortex was determined using immunohistochemistry (IHC).

KEY FINDINGS

The expression of GABAB1, GABAAα1, and mGlu2 receptors increased gradually with age in the male offspring born to Con group while the highest expression was detected in layer IV of the primary visual cortex. In Dia group newborns, the expression of these receptors was significantly reduced in all layers of the primary visual cortex at every three days. Insulin treatment in diabetic mothers restored the expression of these receptors to normal levels in their newborns.

SIGNIFICANCE

The study indicates that diabetes reduces the expression of GABAB1, GABAAα1, and mGlu2 receptors in the primary visual cortex of male offspring born to diabetic rats at P0, P7, and P14. However, insulin treatment can counteract these effects.

Early evolution of glial morphology and inflammatory cytokines following hypoxic-ischemic injury in the newborn piglet brain

Neuroinflammation is a hallmark of hypoxic-ischemic injury and can be characterized by the activation of glial cells and the expression of inflammatory cytokines and chemokines. Interleukin (IL)-1β and tumor necrosis factor (TNF)α are among the best-characterized early response cytokines and are often expressed concurrently. Several types of central nervous system cells secrete IL-1β and TNFα, including microglia, astrocytes, and neurons, and these cytokines convey potent pro-inflammatory actions. Chemokines also play a central role in neuroinflammation by controlling inflammatory cell trafficking. Our aim was to characterise the evolution of early neuroinflammation in the neonatal piglet model of hypoxic-ischemic encephalopathy (HIE). Piglets (< 24 h old) were exposed to HI insult, and recovered to 2, 4, 8, 12 or 24H post-insult. Brain tissue from the frontal cortex and basal ganglia was harvested for assessment of glial cell activation profiles and transcription levels of inflammatory markers in HI piglets with comparison to a control group of newborn piglets. Fluorescence microscopy was used to observe microglia, astrocytes, neurons, degenerating neurons and possibly apoptotic cells, and quantitative polymerase chain reaction was used to measure gene expression of several cytokines and chemokines. HI injury was associated with microglial activation and morphological changes to astrocytes at all time points examined. Gene expression analyses of inflammation-related markers revealed significantly higher expression of pro-inflammatory cytokines tumor necrosis factor-α (TNFα) and interleukin 1 beta (IL-1β), chemokines cxc-chemokine motif ligand (CXCL)8 and CXCL10, and anti-inflammatory cytokine transforming growth factor (TGF)β in every HI group, with some region-specific differences noted. No significant difference was observed in the level of C-X-C chemokine receptor (CCR)5 over time. This high degree of neuroinflammation was associated with a reduction in the number of neurons in piglets at 12H and 24H in the frontal cortex, and the putamen at 12H. This reduction of neurons was not associated with increased numbers of degenerating neurons or potentially apoptotic cells. HI injury triggered a robust early neuroinflammatory response associated with a reduction in neurons in cortical and subcortical regions in our piglet model of HIE. This neuroinflammatory response may be targeted using novel therapeutics to reduce neuropathology in our piglet model of neonatal HIE.

Pathological changes of brain oscillations following ischemic stroke

Brain oscillations recorded in the extracellular space are among the most important aspects of neurophysiology data reflecting the activity and function of neurons in a population or a network. The signal strength and patterns of brain oscillations can be powerful biomarkers used for disease detection and prediction of the recovery of function. Electrophysiological signals can also serve as an index for many cutting-edge technologies aiming to interface between the nervous system and neuroprosthetic devices and to monitor the efficacy of boosting neural activity. In this review, we provided an overview of the basic knowledge regarding local field potential, electro- or magneto- encephalography signals, and their biological relevance, followed by a summary of the findings reported in various clinical and experimental stroke studies. We reviewed evidence of stroke-induced changes in hippocampal oscillations and disruption of communication between brain networks as potential mechanisms underlying post-stroke cognitive dysfunction. We also discussed the promise of brain stimulation in promoting post stroke functional recovery via restoring neural activity and enhancing brain plasticity.

Long-term outcomes of very-low-birth-weight and low-birth-weight preterm newborns with neonatal seizures: A single-center perspective

OBJECTIVE

Newborn seizures are frequent in preterm newborns and indicate brain lesions in many cases. The objective of this observational study was to investigate the long-term outcome of very-low-birth-weight (VLBW) and low-birth-weight (LBW) preterm infants with neonatal seizures.

METHODS

We examined 54 preterm infants (40 VLBW and 14 LBW cases) born between 2008 and 2011 with clinical seizures during the neonatal period confirmed by interictal or ictal electroencephalography recordings in a retrospective single-center study. Neurodevelopmental follow-up included an expert neurological examination and cognitive testing (Kaufman Assessment Battery for Children) at a mean age of six years.

RESULTS

The (mean ± standard deviation) gestational ages of the VLBW and LBW infants were 27.2 ± 1.9 weeks and 33.4 ± 1.7 weeks, respectively, and the postnatal age at seizure onset was 13 ± 11 days in VLBW infants and 9 ± 8 days in LBW infants, with a wide range of one to 62 days. LBW infants more frequently developed non-motor seizures (50.0%) than VLBW infants did (25.0%), and higher-grade intracranial hemorrhage was the predominant etiology in the VLBW group (18.0%), while the etiology in the LBW group was more heterogeneous and included central nervous system malformations and genetic syndromes. At the mean age of 6.2 ± 2.0, years, 25/54 patients were assessed and 44.4% of the VLBW group and 71.4% of the LBW group showed intellectual impairment. Infantile cerebral palsy was present in 22% of VLBW and 42.9% of LBW infants, respectively.

SIGNIFICANCE

The present analysis of long-term neurodevelopmental outcomes of preterm neonates who experienced seizures shows that the risk for intellectual impairment is not limited only to VLBW infants but may significantly affect LBW infants as well. The etiological spectrum differs in relation to gestational age.

Neurovascular Unit Alterations in the Growth-Restricted Newborn Are Improved Following Ibuprofen Treatment

The developing brain is particularly vulnerable to foetal growth restriction (FGR) and abnormal neurodevelopment is common in the FGR infant ranging from behavioural and learning disorders to cerebral palsy. No treatment exists to protect the FGR newborn brain. Recent evidence suggests inflammation may play a key role in the mechanism responsible for the progression of brain impairment in the FGR newborn, including disruption to the neurovascular unit (NVU). We explored whether ibuprofen, an anti-inflammatory drug, could reduce NVU disruption and brain impairment in the FGR newborn. Using a preclinical FGR piglet model, ibuprofen was orally administered for 3 days from birth. FGR brains demonstrated a proinflammatory state, with changes to glial morphology (astrocytes and microglia), and blood-brain barrier disruption, assessed by IgG and albumin leakage into the brain parenchyma and a decrease in blood vessel density. Loss of interaction between astrocytic end-feet and blood vessels was evident where plasma protein leakage was present, suggestive of structural deficits to the NVU. T-cell infiltration was also evident in the parenchyma of FGR piglet brains. Ibuprofen treatment reduced the pro-inflammatory response in FGR piglets, reducing the number of activated microglia and enhancing astrocyte interaction with blood vessels. Ibuprofen also attenuated plasma protein leakage, regained astrocytic end-feet interaction around vessels, and decreased T-cell infiltration into the FGR brain. These findings suggest postnatal administration of ibuprofen modulates the inflammatory state, allowing for stronger interaction between vasculature and astrocytic end-feet to restore NVU integrity. Modulation of the NVU improves the FGR brain microenvironment and may be key to neuroprotection.

Combination of human endothelial colony-forming cells and mesenchymal stromal cells exert neuroprotective effects in the growth-restricted newborn

The foetal brain is particularly vulnerable to the detrimental effects of foetal growth restriction (FGR) with subsequent abnormal neurodevelopment being common. There are no current treatments to protect the FGR newborn from lifelong neurological disorders. This study examines whether pure foetal mesenchymal stromal cells (MSC) and endothelial colony-forming cells (ECFC) from the human term placenta are neuroprotective through modulating neuroinflammation and supporting the brain vasculature. We determined that one dose of combined MSC-ECFCs (cECFC; 10⁶ ECFC 10⁶ MSC) on the first day of life to the newborn FGR piglet improved damaged vasculature, restored the neurovascular unit, reduced brain inflammation and improved adverse neuronal and white matter changes present in the FGR newborn piglet brain. These findings could not be reproduced using MSCs alone. These results demonstrate cECFC treatment exerts beneficial effects on multiple cellular components in the FGR brain and may act as a neuroprotectant.

Neuromonitoring bei zerebralen Anfällen im Neugeborenenalter – Chancen und Herausforderungen

Angesichts der vielen Kinder mit neonatalen Risikofaktoren für erworbene ZNS-Läsionen und zerebrale Anfälle ist das EEG zunehmend relevant für eine optimierte Diagnostik und Therapieüberwachung 1 2. Folgender Artikel gibt einen Überblick über Besonderheiten des neonatalen EEG und über aktuelle Empfehlungen zum Stellenwert des Langzeit-EEG-Monitorings bei neonatalen Anfällen und epileptischen Enzephalopathien im Früh- und Neugeborenalter.

Neuromonitoring in Neonatal-Onset Epileptic Encephalopathies

Considering the wide spectrum of etiologies of neonatal-onset epileptic encephalopathies (EE) and their unfavorable consequences for neurodevelopmental prognoses, neuromonitoring at-risk neonates is increasingly important. EEG is highly sensitive for early identification of electrographic seizures and abnormal background activity. Amplitude-integrated EEG (aEEG) is recommended as a useful bedside monitoring method but as a complementary tool because of methodical limitations. It is of special significance in monitoring neonates with acute symptomatic as well as structural, metabolic and genetic neonatal-onset EE, being at high risk of electrographic-only and prolonged seizures. EEG/aEEG monitoring is established as an adjunctive tool to confirm perinatal hypoxic-ischemic encephalopathy (HIE). In neonates with HIE undergoing therapeutic hypothermia, burst suppression pattern is associated with good outcomes in about 40% of the patients. The prognostic specificity of EEG/aEEG is lower compared to cMRI. As infants with HIE may develop seizures after cessation of hypothermia, recording for at least 24 h after the last seizure is recommended. Progress in the identification of genetic etiology of neonatal EE constantly increases. However, presently, no specific EEG changes indicative of a genetic variant have been characterized, except for individual variants associated with typical EEG patterns (e.g., KCNQ2, KCNT1). Long-term monitoring studies are necessary to define and classify electro-clinical patterns of neonatal-onset EE.

Experimental cortical stroke induces aberrant increase of sharp-wave-associated ripples in the hippocampus and disrupts cortico-hippocampal communication

The functional consequences of ischemic stroke in the remote brain regions are not well characterized. The current study sought to determine changes in hippocampal oscillatory activity that may underlie the cognitive impairment observed following distal middle cerebral artery occlusion (dMCAO) without causing hippocampal structural damage. Local field potentials were recorded from the dorsal hippocampus and cortex in urethane-anesthetized rats with multichannel silicon probes during dMCAO and reperfusion, or mild ischemia induced by bilateral common carotid artery occlusion (CCAO). Bilateral change of brain state was evidenced by reduced theta/delta amplitude ratio and shortened high theta duration following acute dMCAO but not CCAO. An aberrant increase in the occurrence of sharp-wave-associated ripples (150-250 Hz), crucial for memory consolidation, was only detected after dMCAO reperfusion, coinciding with an increased occurrence of high-frequency discharges (250-450 Hz). dMCAO also significantly affected the modulation of gamma amplitude in the cortex coupled to hippocampal theta phase, although both hippocampal theta and gamma power were temporarily decreased during dMCAO. Our results suggest that MCAO may disrupt the balance between excitatory and inhibitory circuits in the hippocampus and alter the function of cortico-hippocampal network, providing a novel insight in how cortical stroke affects function in remote brain regions.

Electroencephalogram studies of hypoxic ischemia in fetal and neonatal animal models

Alongside clinical achievements, experiments conducted on animal models (including primate or non-primate) have been effective in the understanding of various pathophysiological aspects of perinatal hypoxic/ischemic encephalopathy (HIE). Due to the reasonably fair degree of flexibility with experiments, most of the research around HIE in the literature has been largely concerned with the neurodevelopmental outcome or how the frequency and duration of HI seizures could relate to the severity of perinatal brain injury, following HI insult. This survey concentrates on how EEG experimental studies using asphyxiated animal models (in rodents, piglets, sheep and non-human primate monkeys) provide a unique opportunity to examine from the exact time of HI event to help gain insights into HIE where human studies become difficult.

The Roles of GABA in Ischemia-Reperfusion Injury in the Central Nervous System and Peripheral Organs

Ischemia-reperfusion (I/R) injury is a common pathological process, which may lead to dysfunctions and failures of multiple organs. A flawless medical way of endogenous therapeutic target can illuminate accurate clinical applications. γ-Aminobutyric acid (GABA) has been known as a marker in I/R injury of the central nervous system (mainly in the brain) for a long time, and it may play a vital role in the occurrence of I/R injury. It has been observed that throughout cerebral I/R, levels, syntheses, releases, metabolisms, receptors, and transmissions of GABA undergo complex pathological variations. Scientists have investigated the GABAergic enhancers for attenuating cerebral I/R injury; however, discussions on existing problems and mechanisms of available drugs were seldom carried out so far. Therefore, this review would summarize the process of pathological variations in the GABA system under cerebral I/R injury and will cover corresponding probable issues and mechanisms in using GABA-related drugs to illuminate the concern about clinical illness for accurately preventing cerebral I/R injury. In addition, the study will summarize the increasing GABA signals that can prevent I/R injuries occurring in peripheral organs, and the roles of GABA were also discussed correspondingly.

Seizures Are Associated with Blood-Brain Barrier Disruption in a Piglet Model of Neonatal Hypoxic-Ischaemic Encephalopathy

Seizures in the neonatal period are most often symptomatic of central nervous system (CNS) dysfunction and the most common cause is hypoxic-ischaemic encephalopathy (HIE). Seizures are associated with poor long-term outcomes and increased neuropathology. Blood-brain barrier (BBB) disruption and inflammation may contribute to seizures and increased neuropathology but are incompletely understood in neonatal HIE. The aim of this study was to investigate the impact of seizures on BBB integrity in a preclinical model of neonatal hypoxic-ischaemic (HI) injury. Piglets (age: <24 h) were subjected to a 30-min HI insult followed by recovery to 72 h post-insult. Amplitude-integrated electroencephalography (aEEG) was performed and seizure burden and background aEEG pattern were analysed. BBB disruption was evaluated in the parietal cortex and hippocampus by means of immunohistochemistry and Western blot. mRNA and protein expression of tight-junction proteins (zonula-occludens 1 [ZO1], occludin [OCLN], and claudin-5 [CLDN5]) was assessed using quantitative polymerase chain reaction (qPCR) and Western blot. In addition, mRNA from genes associated with BBB disruption vascular endothelial growth factor (VEGF) and matrix metalloproteinase 2 (MMP2) as well as inflammatory cytokines and chemokines was assessed with qPCR. Piglets that developed seizures following HI (HI-Sz) had significantly greater injury, as demonstrated by poorer aEEG background pattern scores, lower neurobehavioural scores, and greater histopathology. HI-Sz animals had severe IgG extravasation into brain tissue and uptake into neurons as well as significantly greater levels of IgG in both brain regions as assessed by Western blot. IgG protein in both brain regions was significantly associated with seizure burden, aEEG pattern scores, and neurobehavioural scores. There was no difference in mRNA expression of the tight junctions, however a significant loss of ZO1 and OCLN protein was observed in the parietal cortex. The inflammatory genes TGFβ, IL1β, IL8, IL6, and TNFα were significantly upregulated in HI-Sz animals. MMP2 was significantly increased in animals with seizures compared with animals without seizures. Increasing our understanding of neuropathology associated with seizure is vital because of the association between seizure and poor outcomes. Investigating the BBB is a major untapped area of research and a potential avenue for novel treatments.

Neuropathology in intrauterine growth restricted newborn piglets is associated with glial activation and proinflammatory status in the brain

BACKGROUND

The fetal brain is particularly vulnerable to intrauterine growth restriction (IUGR) conditions evidenced by neuronal and white matter abnormalities and altered neurodevelopment in the IUGR infant. To further our understanding of neurodevelopment in the newborn IUGR brain, clinically relevant models of IUGR are required. This information is critical for the design and implementation of successful therapeutic interventions to reduce aberrant brain development in the IUGR newborn. We utilise the piglet as a model of IUGR as growth restriction occurs spontaneously in the pig as a result of placental insufficiency, making it a highly relevant model of human IUGR. The purpose of this study was to characterise neuropathology and neuroinflammation in the neonatal IUGR piglet brain.

METHODS

Newborn IUGR (< 5th centile) and normally grown (NG) piglets were euthanased on postnatal day 1 (P1; < 18 h) or P4. Immunohistochemistry was utilised to examine neuronal, white matter and inflammatory responses, and PCR for cytokine analysis in parietal cortex of IUGR and NG piglets.

RESULTS

The IUGR piglet brain displayed less NeuN-positive cells and reduced myelination at both P1 and P4 in the parietal cortex, indicating neuronal and white matter disruption. A concurrent decrease in Ki67-positive proliferative cells and increase in cell death (caspase-3) in the IUGR piglet brain was also apparent on P4. We observed significant increases in the number of both Iba-1-positive microglia and GFAP-positive astrocytes in the white matter in IUGR piglet brain on both P1 and P4 compared with NG piglets. These increases were associated with a change in activation state, as noted by altered glial morphology. This inflammatory state was further evident with increased expression levels of proinflammatory cytokines (interleukin-1β, tumour necrosis factor-α) and decreased levels of anti-inflammatory cytokines (interleukin-4 and -10) observed in the IUGR piglet brains.

CONCLUSIONS

These findings suggest that the piglet model of IUGR displays the characteristic neuropathological outcomes of neuronal and white matter impairment similar to those reported in the IUGR human brain. The activated glial morphology and elevated proinflammatory cytokines is indicative of an inflammatory response that may be associated with neuronal damage and white matter disruption. These findings support the use of the piglet as a pre-clinical model for studying mechanisms of altered neurodevelopment in the IUGR newborn.

Identification and expression of a unique neonatal variant of the GABAA receptor α3 subunit

The GABA_A receptor provides the majority of inhibitory neurotransmission in the adult central nervous system but in immature brain is responsible for much of the excitatory drive, a requirement for normal brain development. It is well established that GABA_A receptor subunit expression changes across the course of brain development. In the present study, we have identified a splice variant of the GABA_A receptor α₃ subunit which appears unique to the developing brain, referred to here as the GABA_A receptor α₃ subunit neonatal variant (GABA_A receptor α_3N). RT-PCR and sequence analysis revealed splicing of exon 8 of the α₃ subunit. Western blot analysis showed expression of GABA_A receptor α_3N in the cortex of several neonatal species and significantly reduced expression of this splice variant in the corresponding adult brains. Expression was evident in multiple brain regions and decreased across development in the pig. Fractionation revealed differential cellular localisation in the parietal cortex, hippocampus and thalamus of the full-length GABA_A receptor α₃ and GABA_A receptor α_3N. Immunoprecipitation showed direct interaction with the GABA_A receptor subunits α₁ and γ₂ but not with gephyrin.

Simple and reproducible approaches for the collection of select porcine ganglia

BACKGROUND

The anatomy and physiology of the pig nervous system is more similar to humans compared to traditional rodent models. This makes the pig an attractive model to answer questions relating to human health and disease. Yet the technical and molecular tools available to pig researchers are limited compared to rodent researchers.

NEW METHOD

We developed simple and rapid methods to isolate the trigeminal, nodose (distal vagal), and dorsal root ganglia from neonatal pigs. We selected these ganglia due to their broad applicability to basic science researchers and clinicians.

RESULTS

Use of these methods resulted in reproducible isolation of all three types of ganglia as validated by histological examination.

COMPARISON WITH EXISTING METHOD(S)

There are currently no methods that describe a step-by-step protocol to isolate these porcine ganglia.

CONCLUSIONS

In conclusion, these methods for ganglia collection will facilitate and accelerate future neuroscience investigations in pig models of human disease.

GABAA receptor expression and white matter disruption in intrauterine growth restricted piglets

Intrauterine growth restriction (IUGR) is one of the most common causes of perinatal mortality and morbidity. White matter and neuronal injury are major pathophysiological features of the IUGR neonatal brain. GABA_A (γ-aminobutyric acid type A) receptors have been shown to play a role in oligodendrocyte differentiation and proliferation in the neonatal brain and may be a key factor in white matter injury and myelination in IUGR neonates. Whether there are impairments to the GABAergic system and neuronal cytoskeleton in IUGR brain has yet to be elucidated. This study aims to examine GABA_A receptor α₁ and α₃ subunit protein expression and distribution in parietal cortex and hippocampus of the IUGR piglet at four different ages (term=115d - days gestational age), 100d, 104d, birth (postnatal day 0-P0) and P7 and to examine neuronal and myelination patterns. Significant alterations to GABA_A receptor α₁ and α₃ protein expression levels were observed in the IUGR piglet brain of P7 IUGR piglets with significantly greater α₃ expression compared to α₁ expression in the hippocampus while there was virtually no difference between the two subunits in the parietal cortex. However a significantly lower α₁/α₃ ratio was evident in P7 IUGR cortex when compared with P7 NG cortex. Neuronal somatodendrites studied using MAP2 immunohistochemistry showed reduced and disrupted somatodendrites while MBP immunolabelling showed loss of axonal fibres from gestational day 104d through to P7. These findings provide insights into the effects of IUGR on the development of the GABA system, altered developmental maturation of GABA_A receptor subunit expression in the IUGR brain may influence myelination and may partly explain the cognitive disabilities observed in IUGR. Understanding the mechanisms behind grey and white matter injury in the IUGR infant is essential to identifying targets for treatments to improve long-term outcomes for IUGR infants.