Neonatal ketamine exposure impairs infrapyramidal bundle pruning and causes lasting increase in excitatory synaptic transmission in hippocampal CA3 neurons

Diurnal dynamics of the Zbtb14 protein in the ventral hippocampus are disrupted in epileptic mice

Our previous in silico data indicated an overrepresentation of the ZF5 motif in the promoters of genes in which circadian oscillations are altered in the ventral hippocampus in the pilocarpine model of temporal lobe epilepsy in mice. In this study, we test the hypothesis that the Zbtb14 protein oscillates in the hippocampus in a diurnal manner and that this oscillation is disrupted by epilepsy. We found that Zbtb14 immunostaining is present in the cytoplasm and cell nuclei. Western blot data indicate that the cytoplasmic and nuclear levels of Zbtb14 protein oscillate, but the phase is shifted. The densities of the Zbtb14-immunopositive cells express diurnal dynamics in the ventral hilus and CA3 but not in the dorsal hilus and CA3, or the somatosensory cortex. In the pilocarpine model of epilepsy, an increase in the level of Zbtb14 protein was found at 11 PM but not at 3 PM compared to controls. Finally, in silico analysis revealed the presence of the ZF5 motif in the promoters of 21 out of 24 genes down-regulated by epileptiform discharges in vitro, many of which are involved in neuronal plasticity. Our data suggest that Zbtb14 may be involved in the diurnal dynamic of seizure regulation or brain response to seizure rhythmicity.

Dexmedetomidine for Less Invasive Surfactant Administration: A Pilot Study

INTRODUCTION

Less invasive surfactant administration (LISA) involves delivering surfactant to a spontaneously breathing infant by passing a thin catheter through the vocal cords and has become the preferred method for surfactant delivery. However, the role of pre-LISA sedation remains unclear.

OBJECTIVE

The aim of this study was to describe the use of dexmedetomidine for LISA in preterm and early-term infants.

METHODS

This retrospective study evaluated preterm and early-term infants who received intravenous dexmedetomidine for LISA between December 2022 and March 2024. Primary outcomes included safety parameters such as the absence of bradycardia, hypotension, hypothermia, or respiratory depression, and the success rate of LISA, determined by the lack of endotracheal intubation within 72 h. Intergroup comparison based on a cutoff of 32 weeks post-menstrual age (PMA) was performed.

RESULTS

Thirty-seven infants were included. The mean ± SD PMA at birth, birth weight, and age at LISA were 32.2 ± 2.7 weeks, 1879 ± 698 g, and 13.9 ± 12.4 h, respectively. Mean dexmedetomidine dosage was 0.66 ± 0.26 μg/kg. Six patients (16.2%) developed mild hypothermia, and 10 (27%) experienced apnea/bradycardia within 24 h. The success rate of the procedure was 89.2%. Infants born before 32 weeks received lower doses of dexmedetomidine than those born at 32 weeks and above (0.54 ± 0.24 versus 0.76 ± 0.24 μg/kg, p < 0.01). Safety and success rates of LISA were similar across groups.

CONCLUSION

This is the first report on dexmedetomidine as pre-LISA sedation, demonstrating its feasibility with comparable success rates regardless of PMA. These findings may inform future studies on sedation strategies for LISA.

Repeated Ketamine Anesthesia during the Neonatal Period Impairs Hippocampal Neurogenesis and Long-Term Neurocognitive Function by Inhibiting Mfn2-Mediated Mitochondrial Fusion in Neural Stem Cells

The mechanism of ketamine-induced neurotoxicity development remains elusive. Mitochondrial fusion/fission dynamics play a critical role in regulating neurogenesis. Therefore, this study was aimed to evaluate whether mitochondrial dynamics were involved in ketamine-induced impairment of neurogenesis in neonatal rats and long-term synaptic plasticity dysfunction. In the in vivo study, postnatal day 7 (PND-7) rats received intraperitoneal (i.p.) injection of 40 mg/kg ketamine for four consecutive times at 1 h intervals. The present findings revealed that ketamine induced mitochondrial fusion dysfunction in hippocampal neural stem cells (NSCs) by downregulating Mitofusin 2 (Mfn2) expression. In the in vitro study, ketamine treatment at 100 μM for 6 h significantly decreased the Mfn2 expression, and increased ROS generation, decreased mitochondrial membrane potential and ATP levels in cultured hippocampal NSCs. For the interventional study, lentivirus (LV) overexpressing Mfn2 (LV-Mfn2) or control LV vehicle was microinjected into the hippocampal dentate gyrus (DG) 4 days before ketamine administration. Targeted Mfn2 overexpression in the DG region could restore mitochondrial fusion in NSCs and reverse the inhibitory effect of ketamine on NSC proliferation and its faciliatory effect on neuronal differentiation. In addition, synaptic plasticity was evaluated by transmission electron microscopy, Golgi-Cox staining and long-term potentiation (LTP) recordings at 24 h after the end of the behavioral test. Preconditioning with LV-Mfn2 improved long-term cognitive dysfunction after repeated neonatal ketamine exposure by reversing the inhibitory effect of ketamine on synaptic plasticity in the hippocampal DG. The present findings demonstrated that Mfn2-mediated mitochondrial fusion dysfunction plays a critical role in the impairment of long-term neurocognitive function and synaptic plasticity caused by repeated neonatal ketamine exposure by interfering with hippocampal neurogenesis. Thus, Mfn2 might be a novel therapeutic target for the prevention of the developmental neurotoxicity of ketamine.

Apamin, an SK2 Inhibitor, Attenuated Neonatal Sevoflurane Exposures Caused Cognitive Deficits in Mice through the Regulation of Hippocampal Neuroinflammation

Cognitive dysfunction induced by anesthesia in the infant is a crucial clinical issue that is still being debated and the focus of concern for the parents. However, the mechanism of cognitive decline caused by anesthesia and the corresponding treatment methods remain unclear. Postnatal day 7 (PND7) C57BL/6 mice included in the study were randomly divided into a control group (Control), a group with repeated exposure to sevoflurane (Sevo), and an Apamin intervention group (Sevo + Apamin). Apamin (0.5 μL at the concentration of 100 nmol/L) was injected into the bilateral hippocampus of mice. qRT-PCR, enzyme-linked immunosorbent assay (ELISA), and western blotting assay were used to evaluate the protein levels in the hippocampus. Object location memory (OLM) and novel object recognition (NOR) tasks, as well as elevated plus maze and contextual and cued fear conditioning tasks were used to evaluate the cognitive function of mice. Apamin mitigated sevoflurane-induced cognitive impairment of mice, sevoflurane-induced neuronal injury, and sevoflurane-induced activation of microglial in the hippocampus of the mice. Apamin inhibited M1-type polarization but promoted M2-type polarization of microglia after neonatal sevoflurane exposures in the hippocampus. In conclusion, Apamin attenuates neonatal sevoflurane exposures that cause cognitive deficits in mice through regulating hippocampal neuroinflammation.

Neonatal sevoflurane exposure induces long-term changes in dendritic morphology in juvenile rats and mice

General anesthetics are potent neurotoxins when given during early development, causing apoptotic deletion of substantial number of neurons and persistent neurocognitive and behavioral deficits in animals and humans. The period of intense synaptogenesis coincides with the peak of susceptibility to deleterious effects of anesthetics, a phenomenon particularly pronounced in vulnerable brain regions such as subiculum. With steadily accumulating evidence confirming that clinical doses and durations of anesthetics may permanently alter the physiological trajectory of brain development, we set out to investigate the long-term consequences on dendritic morphology of subicular pyramidal neurons and expression on genes regulating the complex neural processes such as neuronal connectivity, learning, and memory. Using a well-established model of anesthetic neurotoxicity in rats and mice neonatally exposed to sevoflurane, a volatile general anesthetic commonly used in pediatric anesthesia, we report that a single 6 h of continuous anesthesia administered at postnatal day (PND) 7 resulted in lasting dysregulation in subicular mRNA levels of cAMP responsive element modulator (Crem), cAMP responsive element-binding protein 1 (Creb1), and Protein phosphatase 3 catalytic subunit alpha, a subunit of calcineurin (Ppp3ca) (calcineurin) when examined during juvenile period at PND28. Given the critical role of these genes in synaptic development and neuronal plasticity, we deployed a set of histological measurements to investigate the implications of anesthesia-induced dysregulation of gene expression on morphology and complexity of surviving subicular pyramidal neurons. Our results indicate that neonatal exposure to sevoflurane induced lasting rearrangement of subicular dendrites, resulting in higher orders of complexity and increased branching with no significant effects on the soma of pyramidal neurons. Correspondingly, changes in dendritic complexity were paralleled by the increased spine density on apical dendrites, further highlighting the scope of anesthesia-induced dysregulation of synaptic development. We conclude that neonatal sevoflurane induced persistent genetic and morphological dysregulation in juvenile rodents, which could indicate heightened susceptibility toward cognitive and behavioral disorders we are beginning to recognize as sequelae of early-in-life anesthesia.