Neonatal propofol anesthesia modifies activity‐dependent processes and induces transient hyperlocomotor response to d ‐amphetamine during adolescence in rats

The lateral septum partakes the regulation of propofol-induced anxiety-like behavior

Repeated exposure to propofol during early brain development is associated with anxiety disorders in adulthood, yet the mechanisms underlying propofol-induced susceptibility to anxiety disorders remain elusive. The lateral septum (LS), primarily composed of γ-aminobutyric acidergic (GABAergic) neurons, serves as a key brain region in the regulation of anxiety. However, it remains unclear whether LS GABAergic neurons are implicated in propofol-induced anxiety. Therefore, we conducted c-Fos immunostaining of whole-brain slices from mice exposed to propofol during early life. Our findings indicate that propofol exposure activates GABAergic neurons in the LS. Selective activation of LS GABAergic neurons resulted in increased anxiety-like behavior, while selective inhibition of these neurons reduced such behaviors. These results suggest that the LS is a critical brain region involved in propofol-induced anxiety. Furthermore, we investigated the molecular mechanism of propofol-induced anxiety in the LS. Microglia activation underlies the development of anxiety. Immunofluorescence staining and Western blot analysis of LS revealed activated microglia and significantly elevated levels of phospho-NF-κB p65 protein. Additionally, a decrease in the number of neuronal spines was observed. Our study highlights the crucial role of the LS in the development of anxiety-like behavior in adulthood following childhood propofol exposure, accompanied by the activation of inflammatory pathways.

Early childhood general anesthesia and risk of Attention Deficit Hyperactivity Disorder

BACKGROUND

The relationship between early childhood exposure to general anesthesia (GA) and the risk of developing Attention Deficit Hyperactivity Disorder (ADHD) is still uncertain and previous studies have presented conflicting results. This population-based cohort study aimed to investigate the potential relationship between GA exposure and ADHD risk using propensity score matching (PSM) in a large sample size.

METHODS

The study included 15,072 children aged 0-3 years who received GA and were hospitalized for more than 1 day in Taiwan from 2004 to 2014. The nonexposed group was randomly selected through 1:1 PSM from the Taiwan Maternal and Child Health Database (TMCHD). The primary objectives of this study were to determine the incidence rates (IR) and incidence rate ratios (IRR) of ADHD in the two cohorts, employing Poisson regression models.

RESULTS

The GA group and non-GA group each comprised 7,536 patients. The IR of ADHD was higher in the GA group (122.45 per 10,000 person-years) than in the non-GA group (64.15 per 10,000 person-years), and the IRR of ADHD in the GA group was 1.39 (95% CI: 1.26, 1.55). The study found that the number of times of exposure to GA, duration of exposure, male gender, and central nervous system surgery were significant risk factors for ADHD in the future.

CONCLUSIONS

This study's findings suggest that there is a significant correlation between early childhood exposure to GA and the risk of developing ADHD, and GA may be an important risk factor for ADHD in children undergoing surgery. The study also identified several risk factors for ADHD, including the number of times of exposure to GA, duration of exposure, male gender, and central nervous system surgery.

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.

Neonatal Anesthesia and dysregulation of the Epigenome

Each year, millions of infants and children are anesthetized for medical and surgical procedures. Yet, a substantial body of preclinical evidence suggests that anesthetics are neurotoxins that cause rapid and widespread apoptotic cell death in the brains of infant rodents and non-human primates. These animals have persistent impairments in cognition and behavior many weeks or months after anesthesia exposure, leading us to hypothesize that anesthetics do more than simply kill brain cells. Indeed, anesthetics cause chronic neuropathology in neurons that survive the insult, which then interferes with major aspects of brain development, synaptic plasticity, and neuronal function. Understanding the phenomenon of anesthesia-induced developmental neurotoxicity is of critical public health importance because clinical studies now report that anesthesia in human infancy is associated with cognitive and behavioral deficits. In our search for mechanistic explanations for why a young and pliable brain cannot fully recover from a relatively brief period of anesthesia, we have accumulated evidence that neonatal anesthesia can dysregulate epigenetic tags that influence gene transcription such as histone acetylation and DNA methylation. In this review, we briefly summarize the phenomenon of anesthesia-induced developmental neurotoxicity. We then discuss chronic neuropathology caused by neonatal anesthesia, including disturbances in cognition, socio-affective behavior, neuronal morphology, and synaptic plasticity. Finally, we present evidence of anesthesia-induced genetic and epigenetic dysregulation within the developing brain that may be transmitted intergenerationally to anesthesia-naïve offspring.

The relationship between exposure to general anesthetic agents and the risk of developing an impulse control disorder

Most studies examining the effect of extended exposure to general anesthetic agents (GAAs) have demonstrated that extended exposure induces both structural and functional changes in the central nervous system. These changes are frequently accompanied by neurobehavioral changes that include impulse control disorders that are generally characterized by deficits in behavioral inhibition and executive function. In this review, we will.

Acetyl-l-carnitine does not prevent neurodegeneration in a rodent model of prolonged neonatal anesthesia

Many studies have shown that prolonged or repeated use of general anesthesia early in life can cause an increase in neurodegeneration and lasting changes in behavior. While short periods of general anesthesia appear to be safe, there is a concern about the neurotoxic potential of prolonged or repeated general anesthesia in young children. Unfortunately, the use of general anesthesia in children cannot be avoided. It would be a great benefit to develop a strategy to reduce or reverse anesthesia mitigated neurotoxicity. The mechanisms behind anesthesia related neurotoxicity are unknown, but evidence suggests that mitochondrial dysfunction and abnormal energy utilization are involved. Recent research suggests that a class of compounds known as carnitines may be effective at preventing anesthesia related neurotoxicity by influencing fatty acid metabolism in the mitochondria. However, it is unknown if carnitines can provide protection against changes in behavior associated with early life exposure to anesthesia. Accordingly, we evaluated the neuroprotective potential of acetyl-l-carnitine in 7-day old rats. Rat pups were exposed to 6 h of general anesthesia with sevoflurane or a control condition, with and without acetyl-l-carnitine. The oxygenation level of animals was continuously monitored during sevoflurane exposure, and any animal showing signs of hypoxia was removed from the study. Animals exposed to sevoflurane showed clear signs of neurodegeneration 2 h after sevoflurane exposure. The hippocampus, cortex, thalamus, and caudate putamen all had elevated levels of Fluoro-Jade C staining. Despite the elevated levels of Fluoro-Jade C, few behavioral changes were observed in an independent cohort of animals treated with sevoflurane. Furthermore, acetyl-l-carnitine had little impact on levels of Fluoro-Jade C staining in animals treated with sevoflurane. These data suggest that acetyl-l-carnitine may offer little protection again anesthesia related neurotoxicity in fully oxygenated animals.

Every-other-day feeding exacerbates inflammation and neuronal deficits in 5XFAD mouse model of Alzheimer's disease

Food restriction has been widely associated with beneficial effects on brain aging and age-related neurodegenerative diseases such as Alzheimer's disease. However, previous studies on the effects of food restriction on aging- or pathology-related cognitive decline are controversial, emphasizing the importance of the type, onset and duration of food restriction. In the present study, we assessed the effects of preventive every-other-day (EOD) feeding regimen on neurodegenerative phenotype in 5XFAD transgenic mice, a commonly used mouse model of Alzheimer's disease. EOD feeding regimen was introduced to transgenic female mice at the age of 2 months and the effects on amyloid-β (Aβ) accumulation, gliosis, synaptic plasticity, and blood-brain barrier breakdown were analyzed in cortical tissue of 6-month-old animals. Surprisingly, significant increase of inflammation in the cortex of 5XFAD fed EOD mice was observed, reflected by the expression of microglial and astrocytic markers. This increase in reactivity and/or proliferation of glial cells was accompanied by an increase in proinflammatory cytokine TNF-α, p38 MAPK and EAAT2, and a decrease in GAD67. NMDA receptor subunit 2B, related to glutamate excitotoxicity, was increased in the cortex of 5XFAD-EOD mice indicating additional alterations in glutamatergic signaling. Furthermore, 4 months of EOD feeding regimen had led to synaptic plasticity proteins reduction and neuronal injury in 5XFAD mice. However, EOD feeding regimen did not affect Aβ load and blood-brain barrier permeability in the cortex of 5XFAD mice. Our results demonstrate that EOD feeding regimen exacerbates Alzheimer's disease-like neurodegenerative and neuroinflammatory changes irrespective of Aβ pathology in 5XFAD mice, suggesting that caution should be paid when using food restrictions in the prodromal phase of this neurodegenerative disease.

The influence of propofol anesthesia exposure on nonaversive memory retrieval and expression of molecules involved in memory process in the dorsal hippocampus in peripubertal rats

BACKGROUND

The effects of anesthetic drugs on postoperative cognitive function in children are not well defined and have not been experimentally addressed.

AIMS

The present study aimed to examine the influence of propofol anesthesia exposure on nonaversive hippocampus-dependent learning and biochemical changes involved in memory process in the dorsal hippocampus, in peripubertal rats as the rodent model of periadolescence.

METHODS

The intersession spatial habituation and the novel object recognition tasks were used to assess spatial and nonspatial, nonaversive hippocampus-dependent learning. The exposure to anesthesia was performed after comparably long acquisition phases in both tasks. Behavioral testing lasted for 2 consecutive days (24-hour retention period). Changes in the expression of molecules involved in memory retrieval/reconsolidation were examined in the dorsal hippocampus by Western blot and immunohistochemistry, at the time of behavioral testing.

RESULTS

Exposure to propofol anesthesia resulted in inappropriate assessment of spatial novelty at the beginning of the test session and affected continuation of acquisition in the spatial habituation test. The treatment did not affect recognition of the novel object at the beginning of the test session but it attenuated overall preference to novelty, reflecting retrieval of a weak memory. The expression of phosphorylated extracellular signal-regulated kinase 2 (involved in memory retrieval) was decreased while the level of phosphorylated Ca²⁺ /calmodulin-dependent protein kinase IIα and early growth response protein 1 (involved in memory reconsolidation) was increased in the dorsal hippocampus. The level of Finkel-Biskis-Jinkins murine osteosarcoma viral oncogene homolog B (neuronal activity indicator) was increased in the dorsal dentate gyrus. Enhanced exploratory activity was still evident in the propofol anesthesia exposure (PAE) group 48 hour after the treatment in both tasks.

CONCLUSION

In peripubertal rats, propofol anesthesia exposure affects memory retrieval and acquisition of new learning in the spatial and nonspatial, nonaversive learning tasks 24 hour after the treatment, along with the expression of molecules that participate in memory retrieval/reconsolidation in the dorsal hippocampus. These results may have clinical implications, favoring control of basic cognitive functions in older children after the propofol exposure.

Brain molecular changes and behavioral alterations induced by propofol anesthesia exposure in peripubertal rats

BACKGROUND

Propofol is commonly used in modern anesthesiology. Some findings suggest that it is highly addictive.

AIM

In this study it was examined whether propofol anesthesia exposure was able to induce behavioral alterations and brain molecular changes already described in addictive drug usage in peripubertal rats, during the onset of mid/periadolescence as a developmental period with increasing vulnerability to drug addiction.

METHODS

The expression of D1 dopamine receptor, a dopamine, and cAMP-regulated phosphoprotein with a Mr 32 000; Ca²⁺ /calmodulin-dependent protein kinase IIα; and Finkel-Biskis-Jinkins murine osteosarcoma viral oncogene homolog-B was examined in peripubertal rats 4, 24, and 48 hour after propofol anesthesia exposure by Western blot and immunohistochemistry. Brain regions of interest were the medial prefrontal cortex, the striatum, and the thalamus. Anxiety and behavioral cross-sensitization to d-amphetamine were examined as well.

RESULTS

Significant increase in the expression of dopamine and cAMP-regulated phosphoprotein with a Mr 32 000 phosphorylated at threonine 34, a postsynaptic marker of dopaminergic neurotransmission, and Finkel-Biskis-Jinkins murine osteosarcoma viral oncogene homolog-B, a marker of neuronal activity, was detected in the thalamus of experimental animals 4-24 hour after the treatment, with the accent on the paraventricular thalamic nucleus. Significant increase in the expression of Ca²⁺ /calmodulin-dependent protein kinase IIα phosphorylated at threonine 286, a sensor of synaptic activity, was observed in the prefrontal cortex and the striatum 24 hour after propofol anesthesia exposure. It was accompanied by a significant decrease in Finkel-Biskis-Jinkins murine osteosarcoma viral oncogene homolog-B expression in the striatum. Decreased behavioral inhibition in aversive environment and increased motor response to d-amphetamine in a context-independent manner were observed as well.

CONCLUSION

In peripubertal rats, propofol anesthesia exposure induces transient molecular and behavioral response that share similarities with those reported previously for addictive drugs. In the absence of additional pharmacological manipulation, all detected effects receded within 48 hour after the treatment.

Caffeine combined with sedative/anesthetic drugs triggers widespread neuroapoptosis in a mouse model of prematurity

OBJECTIVES

Caffeine (CAF) and sedative/anesthetic drugs (SADs) are often coadministered to premature infants in the neonatal intensive care unit (NICU). While SAD neurotoxicity in the developing brain is well established, it is not fully clear whether CAF interacts with SADs and whether this interaction is detrimental. Using a mouse model of prematurity, we hypothesized that CAF would increase apoptotic neurotoxicity when coadministered with SADs.

METHODS

Postnatal day 3 mice were treated with vehicle or 80 mg/kg CAF prior to challenge with 6 mg/kg midazolam, 40 mg/kg ketamine, or 40 μg/kg fentanyl. Six hours later, pups were sacrificed for activated caspase 3 (AC3) immunohistochemistry, and number of AC3 positive cells per mm³ throughout neocortex, hippocampus, caudate, thalamus, and colliculi was analyzed.

RESULTS

CAF caused a statistically significant increase in AC3 positive cells when coadministered with midazolam (p = 0.002), ketamine (p = 0.014), or fentanyl (p < 0.001). Our composite dataset suggests that the addition of CAF to these SADs has a supra-additive effect, causing more neurotoxicity than expected.

CONCLUSIONS

CAF may augment the neurotoxic action of SADs indicated for neonatal sedation/anesthesia in the NICU by triggering widespread apoptosis in the developing brains of premature infants.

The Fas Ligand/Fas Death Receptor Pathways Contribute to Propofol-Induced Apoptosis and Neuroinflammation in the Brain of Neonatal Rats

A number of experimental studies have reported that exposure to common, clinically used anesthetics induce extensive neuroapoptosis and cognitive impairment when applied to young rodents, up to 2 weeks old, in phase of rapid synaptogenesis. Propofol is the most used general anesthetic in clinical practice whose mechanisms of neurotoxicity on the developing brain remains to be examined in depth. This study investigated effects of different exposures to propofol anesthesia on Fas receptor and Fas ligand expressions, which mediate proapoptotic and proinflammation signaling in the brain. Propofol (20 mg/kg) was administered to 7-day-old rats in multiple doses sufficient to maintain 2-, 4- and 6-h duration of anesthesia. Animals were sacrificed at 0, 4, 16 and 24 h after termination of anesthesia. It was found that propofol anesthesia induced Fas/FasL and downstream caspase-8 expression more prominently in the thalamus than in the cortex. Opposite, Bcl-2 and caspase-9, markers of intrinsic pathway activation, were shown to be more influenced by propofol treatment in the cortex. Further, we have established upregulation of caspase-1 and IL-1β cytokine transcription as well as subsequent activation of microglia that is potentially associated with brain inflammation. Behavioral analyses revealed that P35 and P60 animals, neonatally exposed to propofol, had significantly higher motor activity during three consecutive days of testing in the open field, though formation of the intersession habituation was not prevented. This data, together with our previous results, contributes to elucidation of complex mechanisms of propofol toxicity in developing brain.