Testosterone is Sufficient to Impart Susceptibility to Isoflurane Neurotoxicity in Female Neonatal Rats

Neonatal Diazepam Exposure Decreases Dendritic Arborization and Spine Density of Cortical Pyramidal Neurons in Rats

OBJECTIVE

Benzodiazepines are extensively utilized in pediatric anesthesia and critical care for their anxiolytic and sedative properties. However, preclinical studies indicate that neonatal exposure to GABAergic drugs, including benzodiazepines, leads to long-term cognitive deficits, potentially mediated by altered GABAergic signaling during brain development. This preclinical study investigated the impact of early-life diazepam exposure on cortical neuronal morphology, specifically exploring dendritic arborization and spine density, crucial factors in synaptogenesis.

METHODS

Male and female Sprague Dawley rat pups were exposed to a single neonatal dose of diazepam (30 mg/kg) or vehicle on postnatal day (PND) 7. Golgi-Cox staining was used to assess cortical pyramidal neuron development at 4 developmental stages: neonatal (PND8), infantile (PND15), juvenile (PND30), and adolescence (PND42). Animals were randomized equally to 4 groups: male-vehicle, male-diazepam, female-vehicle, and female-diazepam. Neuronal morphology was evaluated after reconstruction in neurolucida, and dendritic spine density was analyzed through high-power photomicrographs using ImageJ.

RESULTS

Diazepam exposure resulted in decreased dendritic complexity in both sexes, with reduced arborization and spine density observed in cortical pyramidal neurons. Significant differences were found at each developmental stage, indicating a persistent impact. Dendritic length increased with age but was attenuated by diazepam exposure. Branching length analysis revealed decreased complexity after diazepam treatment. Spine density at PND42 was significantly reduced in both apical and basal dendrites after diazepam exposure.

CONCLUSIONS

Neonatal diazepam exposure adversely affected cortical pyramidal neuron development, leading to persistent alterations in dendritic arborization and spine density. These structural changes suggest potential risks associated with early-life diazepam exposure. Further research is needed to unravel the functional consequences of these anatomic alterations.

Neuroprotective effects of testosterone on sevoflurane-induced neurotoxicity in testosterone-deprived male mice

This study aims to investigate whether androgen deprivation, simulating conditions of aging or disease-induced low testosterone levels, increases the susceptibility of male mice to sevoflurane neurotoxicity, and whether testosterone supplementation can reverse the toxic effects of sevoflurane. In here, young male mice were subjected to orchiectomy (ORC) to induce testosterone deprivation. Various techniques, including western blotting, immunofluorescence, Morris Water Maze, Golgi staining, and neuronal signal measurement, were used to evaluate the effects of sevoflurane on long-term (ORC 10 weeks) and short-term (ORC 2 weeks) testosterone deprivation, and assess whether testosterone (1 mg/kg 1 h before sevoflurane exposure) could mitigate sevoflurane-induced neurotoxicity. Flutamide and anastrozole were administered to study testosterone's pathways of action. We found that sevoflurane increased tau phosphorylation and decreased the transient amplitude of Ca2+ signals and dendritic spine density in dorsal hippocampal CA1 (dCA1) neurons, leading to cognitive impairment in testosterone-deprived male mice. Testosterone treatment reversed the effects of sevoflurane in short-term testosterone-deprived male mice, but not in long-term testosterone-deprived male mice. Additionally, the neuroprotective effect of testosterone was blocked by flutamide rather than anastrozole. We have discovered for the first time that testosterone can mitigate the sevoflurane-induced neurotoxicity in testosterone-deprived male mice and that there exists a therapeutic time window, which may be mediated by androgen receptors. This may provide new insights into the neuroprotective role of sex hormones.

Neonatal Cannabidiol Exposure Impairs Spatial Memory and Disrupts Neuronal Dendritic Morphology in Young Adult Rats

Introduction: Early life is a sensitive period for brain development. Perinatal exposure to cannabis is increasingly linked to disruption of neurodevelopment; however, research on the effects of cannabidiol (CBD) on the developing brain is scarce. In this study, we aim to study the developmental effects of neonatal CBD exposure on behavior and dendritic architecture in young adult rats. Materials and Methods: Male and female neonatal Sprague Dawley rats were treated with CBD (50 mg/kg) intraperitoneally on postnatal day (PND) 1, 3, and 5 and evaluated for behavioral and neuronal morphological changes during early adulthood. Rats were subjected to a series of behavioral tasks to evaluate long-term effects of neonatal CBD exposure, including the Barnes maze, open field, and elevated plus maze paradigms to assess spatial memory and anxiety-like behavior. Following behavioral evaluation, animals were sacrificed, and neuronal morphology of the cortex and hippocampus was assessed using Golgi-Cox (GC) staining. Results: Rats treated with CBD displayed a sexually dimorphic response in spatial memory, with CBD-treated females developing a deficit but not males. CBD did not elicit alterations in anxiety-like behavior in either sex. Neonatal CBD caused an overall decrease in dendritic length and spine density (apical and basal) in cortical and hippocampal neurons in both sexes. Sholl analysis also revealed a decrease in dendritic intersections in the cortex and hippocampus, indicating reduced dendritic arborization. Conclusions: This study provides evidence that neonatal CBD exposure perturbs normal brain development and leads to lasting alterations in spatial memory and neuronal dendrite morphology in early adulthood, with sex-dependent sensitivity.

Drug target genes and molecular mechanism investigation in isoflurane-induced anesthesia based on WGCNA and machine learning methods

PURPOSE

This study sought to identify drug target genes and their associated molecular mechanisms during isoflurane-induced anesthesia in clinical applications.

METHODS

Microarray data (ID: GSE64617; isoflurane-treated vs. normal samples) were downloaded from the Gene Expression Omnibus database. Differentially expressed genes (DEGs) were screened and hub genes were investigated using weighted correlation network analysis (WGCNA). Protein-protein interactions (PPIs) were constructed among the co-DEGs (common genes between DEGs and hub genes), followed by functional enrichment analyses. Then, three machine learning methods were used to reveal drug targets, followed by validation, nomogram analysis, and gene set enrichment analysis. Finally, an miRNA-target network was constructed.

RESULTS

A total of 686 DEGs were identified between the two groups-of which, 183 DEGs integrated with genes revealed by WCGNA were identified as co-genes. These genes, including contactin-associated protein 1 (CNTNAP1), are mainly involved in functions such as action potentials. PPI network analysis revealed three models, with the machine learning analysis exploring four drug target genes: A2H, FAM155B, SCARF2, and SDR16C5. ROC and nomogram analyses demonstrated the ideal diagnostic value of these target genes. Finally, miRNA-mRNA pairs were constructed based on the four mRNAs and associated 174 miRNAs.

CONCLUSION

FA2H, FAM155B, SCARF2, and SDR16C5 may be novel drug target genes for isoflurane-induced anesthesia. CNTNAP1 may participate in the progression of isoflurane-induced anesthesia via its action potential function.

Do We Have Viable Protective Strategies against Anesthesia-Induced Developmental Neurotoxicity?

Since its invention, general anesthesia has been an indispensable component of modern surgery. While traditionally considered safe and beneficial in many pathological settings, hundreds of preclinical studies in various animal species have raised concerns about the detrimental and long-lasting consequences that general anesthetics may cause to the developing brain. Clinical evidence of anesthetic neurotoxicity in humans continues to mount as we continue to contemplate how to move forward. Notwithstanding the alarming evidence, millions of children are being anesthetized each year, setting the stage for substantial healthcare burdens in the future. Hence, furthering our knowledge of the molecular underpinnings of anesthesia-induced developmental neurotoxicity is crucially important and should enable us to develop protective strategies so that currently available general anesthetics could be safely used during critical stages of brain development. In this mini-review, we provide a summary of select strategies with primary focus on the mechanisms of neuroprotection and potential for clinical applicability. First, we summarize a diverse group of chemicals with the emphasis on intracellular targets and signal-transduction pathways. We then discuss epigenetic and transgenerational effects of general anesthetics and potential remedies, and also anesthesia-sparing or anesthesia-delaying approaches. Finally, we present evidence of a novel class of anesthetics with a distinct mechanism of action and a promising safety profile.