Hypoxia-ischaemia (HI) in term infants is a common cause of brain injury and neurodevelopmental impairment. Development of gamma-aminobutyric acid (GABA)ergic circuitry in the cerebral cortex is a critical event in perinatal brain development. Perineuronal nets (PNNs) are specialised extracellular matrix structures that surround GABAergic interneurons, and are important for their function. Herein, we hypothesised that HI would reduce survival of cortical interneurons and disrupt PNNs in a near-term fetal sheep model of global cerebral ischaemia. Fetal sheep (0.85 gestation) received sham occlusion (n = 5) or 30 min of reversible cerebral ischaemia (HI group; n = 5), and were recovered for 7 days. Expression of interneurons (glutamate decarboxylase [GAD]+; parvalbumin [PV]+) and PNNs (Wisteria floribunda agglutinin, WFA) was assessed in the parasagittal cortex by immunohistochemistry. HI was associated with marked loss of both GAD+ and PV+ cortical interneurons (all layers of the parasagittal cortex and layer 6) and PNNs (layer 6). The expression and integrity of PNNs was also reduced on surviving GAD+ interneurons. There was a trend towards a linear correlation of the proportion of GAD+ neurons that were WFA+ with seizure burden (r2 = 0.76, p = 0.0534). Overall, these data indicate that HI may cause deficits in the cortical GABAergic system involving loss of interneurons and disruption of PNNs, which may contribute to the range of adverse neurological outcomes following perinatal brain injury.

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Perinatal hypoxia-ischemia is associated with disruption of cortical gamma-aminobutyric acid (GABA)ergic interneurons and their surrounding perineuronal nets, which may contribute to persisting neurological deficits. Blockade of connexin43 hemichannels using a mimetic peptide can alleviate seizures and injury after hypoxia-ischemia. In this study, we tested the hypothesis that connexin43 hemichannel blockade improves the integrity of cortical interneurons and perineuronal nets. Term-equivalent fetal sheep received 30 min of bilateral carotid artery occlusion, recovery for 90 min, followed by a 25-h intracerebroventricular infusion of vehicle or a mimetic peptide that blocks connexin hemichannels or by a sham ischemia + vehicle infusion. Brain tissues were stained for interneuronal markers or perineuronal nets. Cerebral ischemia was associated with loss of cortical interneurons and perineuronal nets. The mimetic peptide infusion reduced loss of glutamic acid decarboxylase-, calretinin-, and parvalbumin-expressing interneurons and perineuronal nets. The interneuron and perineuronal net densities were negatively correlated with total seizure burden after ischemia. These data suggest that the opening of connexin43 hemichannels after perinatal hypoxia-ischemia causes loss of cortical interneurons and perineuronal nets and that this exacerbates seizures. Connexin43 hemichannel blockade may be an effective strategy to attenuate seizures and may improve long-term neurological outcomes after perinatal hypoxia-ischemia.

Despite the prevalence of preterm brain injury, there are no established neuroprotective strategies to prevent or alleviate mild-to-moderate inflammation-related brain injury. Perinatal infection and inflammation have been shown to trigger acute neuroinflammation, including proinflammatory cytokine release and gliosis, which are associated with acute and chronic disturbances in brain cell survival and maturation. These findings suggest the hypothesis that the inhibition of peripheral immune responses following infection or nonspecific inflammation may be a therapeutic strategy to reduce the associated brain injury and neurobehavioral deficits. This review provides an overview of the neonatal immunity, neuroinflammation, and mechanisms of inflammation-related brain injury in preterm infants and explores the safety and efficacy of anti-inflammatory agents as potentially neurotherapeutics.

Therapeutic hypothermia significantly improves outcomes after neonatal hypoxic-ischemic (HI) encephalopathy but is only partially protective. There is evidence that cortical inhibitory interneuron circuits are particularly vulnerable to HI and that loss of interneurons may be an important contributor to long-term neurological dysfunction in these infants. In the present study, we examined the hypothesis that the duration of hypothermia has differential effects on interneuron survival after HI. Near-term fetal sheep received sham ischemia or cerebral ischemia for 30 min, followed by cerebral hypothermia from 3 h after ischemia end and continued up to 48 h, 72 h, or 120 h recovery. Sheep were euthanized after 7 days for histology. Hypothermia up to 48 h recovery resulted in moderate neuroprotection of glutamate decarboxylase (GAD)+ and parvalbumin+ interneurons but did not improve survival of calbindin+ cells. Hypothermia up to 72 h recovery was associated with significantly increased survival of all three interneuron phenotypes compared with sham controls. By contrast, while hypothermia up to 120 h recovery did not further improve (or impair) GAD+ or parvalbumin+ neuronal survival compared with hypothermia up to 72 h, it was associated with decreased survival of calbindin+ interneurons. Finally, protection of parvalbumin+ and GAD+ interneurons, but not calbindin+ interneurons, with hypothermia was associated with improved recovery of electroencephalographic (EEG) power and frequency by day 7 after HI. The present study demonstrates differential effects of increasing the duration of hypothermia on interneuron survival after HI in near-term fetal sheep. These findings may contribute to the apparent preclinical and clinical lack of benefit of very prolonged hypothermia.

1100 Introduction: Aspirin is the cornerstone of antiplatelet therapy in patients with coronary artery disease (Lancet 1997; 350: 437–439). However, a substantial proportion of patients manifest “breakthrough” events despite regular intake of aspirin suggesting therapeutic resistance to aspirin. Unfortunately, aspirin resistance remains a poorly defined term. There are conflicting reports on the prevalence of aspirin resistance in India. Materials and Methods: We evaluated the prevalence of pharmacological resistance to aspirin therapy in patients with stable and unstable coronary artery disease at a tertiary center in India. One hundred and twenty six patients aged ≥21 with recorded history of previous myocardial infarction (MI) and/or angiographically proven coronary artery disease undergoing routine outpatient cardiac care were enrolled in the study. Eligible patients were recruited 7days after ensuring compliance with a single formulation of aspirin (enteric coated aspirin 150 mg). Compliance was determined by obtaining a history of drug ingestion and performing a pill count. Patients with history of bleeding disorders and those consuming clopidogrel, dipyridamole, or non-steroidal anti- inflammatory drugs were excluded from study. Platelet function analysis was performed using the technique of optical aggregometry (Chronolog 490D, PA, USA). The following agonists (concentrations in parenthesis) were used: ADP (5 μM), Arachidonic acid (0.5 mg/mL), Collagen (2 μg/mL), and Epinephrine (5 μM). A healthy control was run every time a batch of tests was run for subjects. Pharmacological aspirin resistance was defined as the combined demonstration of mean platelet aggregation of ≥ 70% with ADP and a mean aggregation of ≥20% with Arachidonic acid in patients compliant with aspirin therapy. Patients satisfying either one of the above criteria were considered semi-responders (Am J Cardiol 2001; 88:230-5). Results: Out of a total of 126 patients with stable CAD, 64 % were responders, 36 % were non responders (semi-responders = 34% and resistant = 2%). All the patients with acute coronary syndrome (n = 7) were found to be semi-responders. Aspirin resistance did not show any statistically significant correlation with CAD risk factors like history of smoking, diabetes, obesity and hypertension. Of the laboratory parameters, only the total leukocyte count was significantly associated with the presence of aspirin resistance (p<0.03). Surprisingly, this relationship did not extend to either the absolute lymphocyte or neutrophil count. The other laboratory parameters such as hemoglobin, platelet count, hematocrit, mean cell volume, total protein, and albumin did not show any significant statistical relationship with aspirin resistance. To overcome the influence of preanalytical variables, platelet aggregation studies were repeated randomly on 50% of the study population. Paired analysis did not reveal any major changes among the responders and semi responders although the two resistant patients became semi-responders. Conclusion: Pharmacological resistance or semi-responsiveness to aspirin is prevalent in Indian patients with stable coronary artery disease. Long term follow up of these patients to ascertain their clinical outcome will assist in determining the clinical importance of this phenomenon. Disclosures: No relevant conflicts of interest to declare.