Brain pathology caused in the neonatal macaque by short and prolonged exposures to anticonvulsant drugs

Abstract

Barbiturates and benzodiazepines are potent GABA A receptor agonists and strong anticonvulsants. In the developing brain they can cause neuronal and oligodendroglia apoptosis, impair synaptogenesis, inhibit neurogenesis and trigger long-term neurocognitive sequelae. In humans, the vulnerable period is projected to extend from the third trimester of pregnancy to the third year of life. Infants with seizures and epilepsies may receive barbiturates, benzodiazepines and their combinations for days, months or years. How exposure duration affects neuropathological sequelae is unknown. Here we investigated toxicity of phenobarbital/midazolam (Pb/M) combination in the developing nonhuman primate brain. Neonatal rhesus monkeys received phenobarbital intravenously, followed by infusion of midazolam over 5 ( n = 4) or 24 h (n = 4). Animals were euthanized at 8 or 36 h and brains examined immunohistochemically and stereologically. Treatment was well tolerated, physiological parameters remained at optimal levels. Compared to naive controls, Pb/M exposed brains displayed widespread apoptosis affecting neurons and oligodendrocytes. Pattern and severity of cell death differed depending on treatment-duration, with more extensive neurodegeneration following longer exposure. At 36 h, areas of the brain not affected at 8 h displayed neuronal apoptosis, while oligodendroglia death was most prominent at 8 h. A notable feature at 36 h was degeneration of neuronal tracts and trans-neuronal death of neurons, presumably following their disconnection from degenerated presynaptic partners. These findings demonstrate that brain toxicity of Pb/M in the neonatal primate brain becomes more severe with longer exposures and expands trans-synaptically. Impact of these sequelae on neurocognitive outcomes and the brain connectome will need to be explored.

Seizure burden in preterm infants and smaller brain volume at term-equivalent age

“…However, caution should be urged at this juncture as the data on antiepileptic medications in the preterm population are limited and primarily retrospective in nature. This concern is further highlighted by the neurodevelopmental risks associated with use of antiepileptic drugs in neonates ( 56 ), specifically phenobarbital ( 57 , 58 ), the conventional first-line seizure treatment. While phenobarbital remains the most commonly used treatment ( 2 , 59 ), treatment failure rates as high as 63% have been reported ( 2 ).…”

Mild hypothermia fails to protect infant macaques from brain injury caused by prolonged exposure to Antiseizure drugs

“…Perfusion fixation was performed with 4% paraformaldehyde in phosphate buffer by a trained pathologist according to institutional euthanasia standards. This is the same control group we used in previously published work ( Ikonomidou et al, 2019 ; Noguchi et al, 2021 ).…”

“…Interference with this neurotransmitter system may trigger adverse effects in the immature brain. Over the past two decades, we and many other investigators reported that compounds which positively modulate GABA A receptors, including barbiturates, benzodiazepines, alcohol and volatile anesthetics, trigger apoptosis of neurons and oligodendroglia in the rodent and nonhuman primate brain ( Ikonomidou et al, 2000 ; Brambrink et al, 2012 ; Brambrink et al, 2010 ; Noguchi et al, 2021 ), suppress neurogenesis ( Stefovska et al, 2008 ), inhibit normal synapse development and maturation ( Forcelli et al, 2012 ; Jevtovic-Todorovic et al, 2013 ) and cause long-lasting behavioral and cognitive impairments ( Fredriksson et al, 2007 ; Jevtovic-Todorovic et al, 2003 ; Stefovska et al, 2008 ; Paule et al, 2011 ), when exposure occurs during a period of rapid brain growth. In humans, this brain growth spurt period starts in the third trimester of gestation and extends to the third year of life ( Dobbing and Sands, 1979 ).…”

“…Pattern and severity of cell death differed depending on treatment-duration, with substantially enhanced neurodegeneration detected following the longer 24 h exposure. The findings allowed to conclude that brain toxicity of Pb/M in the neonatal primate brain becomes more severe with longer duration of treatment and expands trans-synaptically ( Noguchi et al, 2021 ).…”

Effects of Midazolam on the Development of Adult Leydig Cells From Stem Cells In Vitro

“…Due to its unique properties for sedation, hypnosis, antianxiety, anterograde amnesia, and central muscle relaxation, and as an anticonvulsant, midazolam is among the top choices for managing sedation and epilepsy in children and adolescents (15)(16)(17)(18)(19)(20). Since the drug can be used repeatedly for an extended period of time, its potential negative effects on neural development has been previously evaluated (21)(22)(23)(24). It has been found that midazolam usage during puberty may affect brain development (25,26).…”