Early Developmental Exposure to Repetitive Long Duration of Midazolam Sedation Causes Behavioral and Synaptic Alterations in a Rodent Model of Neurodevelopment

Abstract

There is a large body of preclinical literature suggesting that exposure to general anesthetic agents during early life may have harmful effects on brain development. Patients in intensive care settings are often treated for prolonged periods with sedative medications, many of which have mechanisms of action that are similar to general anesthetics. Using in vivo studies of the mouse hippocampus and an in vitro rat cortical neuron model we asked whether there is evidence that repeated, long duration exposure to midazolam, a commonly used sedative in pediatric intensive care practice, has the potential to cause lasting harm to the developing brain. We found that mice that underwent midazolam sedation in early postnatal life exhibited deficits in the performance on Y maze and fear conditioning testing at young adult ages. Labeling with a nucleoside analog revealed a reduction in the rate of adult neurogenesis in the hippocampal dentate gyrus, a brain region that has been shown to be vulnerable to developmental anesthetic neurotoxicity. Additionally, using immunohistochemistry for synaptic markers we found that the number of pre-synaptic terminals in the dentate gyrus was reduced, while the number of excitatory post-synaptic terminals was increased. These findings were replicated in a midazolam sedation exposure model in neurons in culture. We conclude that repeated, long duration exposure to midazolam during early development has the potential to result in persistent alterations in the structure and function of the brain.

Cognitive Dysfunction After Analgesia and Sedation: Out of the Operating Room and Into the Pediatric Intensive Care Unit

“…Because much of the aforementioned investigation has been performed in prenatal or infant-approximate animals during neurogenesis, gliogenesis, and synaptogenesis, there is little accounting for the peak of myelination or synaptic pruning and plasticity of later childhood. For example, Briner and DeRoo's anesthetic work been replicated by Xu et al (2019) in early childhood-approximate mice treated with midazolam for 5 days, affirming increased synaptic density at a time when experiential-based pruning should predominate. This effect may be purely neuronal, but synaptic plasticity is chaperoned by astrocytes and microglia, and drug effects in this regard have not been adequately characterized.…”

Early-life midazolam exposure persistently changes chromatin accessibility to impair adult hippocampal neurogenesis and cognition

“…Measuring Anesthetic Score and Duration of MDZ Anesthesia. The anesthetic effects of MDZ in P7 mice were evaluated by righting reflex score and duration time as described previously with some modifications (15,16). For the righting reflex scale, a mouse was placed on its back and the response assessed.…”

“…1 A ) to investigate whether repeated early postnatal exposure to anesthetics affects NSC behavior in the hippocampal DG. The required dose of MDZ for anesthesia in P7 mice was determined based on the anesthetic score ( 15 , 16 ), and MDZ treatment at 10 mg/kg was sufficient to exert its anesthetic effects without causing apparent signs of nutritional deficiency, such as obvious loss of body weight ( SI Appendix , Fig. S1 A – C ).…”

“…These data suggest that MDZ directly inhibits NSC activation and augments their dormancy, possibly through GABA signaling. Since inhibiting NSC activation generally leads to a reduction in the number of newly generated neurons in the DG ( 17 ) and previous studies demonstrated that early-life exposure to anesthetics including MDZ reduces neurogenesis ( 4 , 15 , 18 ), we examined neurogenesis in our experimental setting ( Fig. 1 E ).…”

Anestesia general en infantes: consideraciones neurobiológicas y neuropsicológicas

“…Coincidentemente, es durante estos periodos (alrededor del primer año de vida posnatal) cuando el receptor GABA se vuelve «funcional» al evolucionar de un estado inicial en el que, paradójicamente, funciona excitando a la neurona inmadura, a una conformación madura en la que se convierte en el principal inhibidor de la actividad nerviosa 26 . En estudios preclínicos que evalúan el efecto del midazolam (uno de los ansiolíticos con acción GABA-érgica más utilizados en la práctica anestésica) se ha comprobado que la exposición a este agente durante los picos del desarrollo cerebral eleva la tasa de apoptosis cortical, deteriora la actividad sináptica hipocampal e induce deterioro cognitivo en los sujetos expuestos 32,38,39 . Más recientemente, la sospecha de un efecto neurotóxico se ha extendido también a los agentes adrenérgicos; en particular, la dexmedetomidina llama la atención por su amplio uso en las unidades pediátricas de cuidados intensivos [40][41][42] .…”