These results support the possibility that excitatory output of sevoflurane-potentiated gamma-aminobutyric acid type A/glycine systems may contribute to epileptogenic and neurotoxic effects in early postnatal rats.

Background 1.5 million children under 12 months of age are exposed to general anesthesia annually in the United States alone. Human and especially animal studies provide evidence that exposure to general anesthesia during the early postnatal period may lead to long-term neurocognitive abnormalities via poorly understood mechanisms. We investigated whether an immature stress response system and γ-aminobutyric acid (GABA) type A receptor activities are involved in mediating these abnormalities. Methods Sprague-Dawley rats at postnatal days 4, 5 or 6 were anesthetized with 2.1% sevoflurane for 6 hrs; maternally separated and house reared rats served as controls. Results Sevoflurane anesthesia markedly increased corticosterone levels in rat pups of both genders. In adulthood, these rats responded to stress with heightened secretion of corticosterone and a greater increase in corticosterone levels in males versus females. Only male rats, previously exposed to neonatal sevoflurane, had a higher frequency of miniature inhibitory postsynaptic currents in CA1 neurons, spent a shorter time in open arms of the elevated plus maze (EPM) and exhibited impaired prepulse inhibition (PPI) of startle. Pretreatment of male rats prior to sevoflurane with the Na+-K+-2Cl− cotransporter inhibitor, bumetanide, or the mineralocorticoid receptor antagonist, RU28318, normalized endocrine responses to stress and the EPM behavior in adulthood, while only those pretreated with bumetanide exhibited normalized PPI of startle responses. Neither bumetanide nor RU28318 altered the effect of sevoflurane on synaptic activity. Conclusions Sevoflurane-enhanced neuronal excitation and elevated corticosteroid levels at the time of anesthesia contribute to the mechanisms initiating neonatal sevoflurane-induced long-term endocrine and neurobehavioral abnormalities.

Editor’s Perspective What We Already Know about This Topic What This Article Tells Us That Is New Background Sevoflurane administered to neonatal rats induces neurobehavioral abnormalities and epigenetic reprogramming of their germ cells; the latter can pass adverse effects of sevoflurane to future offspring. As germ cells are susceptible to reprogramming by environmental factors across the lifespan, the authors hypothesized that sevoflurane administered to adult rats could induce neurobehavioral abnormalities in future offspring, but not in the exposed rats themselves. Methods Sprague-Dawley rats were anesthetized with 2.1% sevoflurane for 3 h every other day between postnatal days 56 and 60. Twenty-five days later, exposed rats and nonexposed controls were mated to produce offspring. Results Adult male but not female offspring of exposed parents of either sex exhibited deficiencies in elevated plus maze (mean ± SD, offspring of both exposed parents vs. offspring of control parents, 35 ± 12 vs. 15 ± 15 s, P < 0.001) and prepulse inhibition of acoustic startle (offspring of both exposed parents vs. offspring of control parents, 46.504 ± 13.448 vs. 25.838 ± 22.866%, P = 0.009), and increased methylation and reduced expression of the potassium ion-chloride ion cotransporter KCC2 gene (Kcc2) in the hypothalamus. Kcc2 was also hypermethylated in sperm and ovary of the exposed rats. Surprisingly, exposed male rats also exhibited long-term abnormalities in functioning of the hypothalamic-pituitary-gonadal and -adrenal axes, reduced expression of hypothalamic and hippocampal Kcc2, and deficiencies in elevated plus maze (sevoflurane vs. control, 40 ± 24 vs. 25 ± 12 s, P = 0.038) and prepulse inhibition of startle (sevoflurane vs. control, 39.905 ± 21.507 vs. 29.193 ± 24.263%, P < 0.050). Conclusions Adult sevoflurane exposure affects brain development in male offspring by epigenetically reprogramming both parental germ cells, while it induces neuroendocrine and behavioral abnormalities only in exposed males. Sex steroids may be required for mediation of the adverse effects of adult sevoflurane in exposed males.

Neonatal exposure to sevoflurane can affect the next generation of males through epigenetic modification of Kcc2 expression, while F1 females are at diminished risk.

Background We sought whether subjects with pathophysiological conditions that are characterized by elevated levels of aldosterone have increased susceptibility to the side effects of neonatal anesthesia with sevoflurane. Methods Postnatal day 4–20 (P4–P20) rats were exposed to 6% and 2.1% sevoflurane for 3 min and 60–360 min, respectively. Exogenous aldosterone was administered to imitate pathophysiological conditions with elevated levels of aldosterone. Results Six hours of anesthesia with sevoflurane on P4–P5 resulted in more than 30-fold increase in serum levels of aldosterone (7.02 ± 1.61 ng/dl vs. 263.75 ± 22.31 ng/dl, mean ± SE, n = 5–6) and reduced prepulse inhibition of the acoustic startle response (F(2,37)= 5.66, P<0.001). Administration of exogenous aldosterone during anesthesia with sevoflurane further enhanced seizure-like electroencephalogram patterns in neonatal rats (48.25±15.91 s vs. 222.00 ± 53.87 s, mean± SE, n = 4), but did not affect electroencephalographic activity in older rats. Exogenous aldosterone increased activation of caspase-3 (F(3,28)=11.02, P<0.001) and disruption of prepulse inhibition of startle (F(3,46)=6.36; P= 0.001) caused by sevoflurane. Intracerebral administration of oxytocin receptor agonists resulted in depressed seizure-like electroencephalogram patterns (F(2,17)=6.37, P=0.009), reduced activation of caspase-3 ((t(11) = 2.83, P = 0.016) and disruption of PPI of startle (t(7) = −2.9; P = 0.023) caused by sevoflurane. Conclusions These results suggest that adverse developmental effects of neonatal anesthesia with sevoflurane may involve both central and peripheral actions of the anesthetic. Subjects with elevated levels of aldosterone may be more vulnerable, while intracerebral oxytocin receptor agonists may be neuroprotective.

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(Br J Anaesth. 2018;121:406–416) Neonatal anesthesia-induced abnormalities and their mechanisms are poorly understood, even in exposed animals. Some studies have shown that rats, especially male rats, develop behavioral deficiencies and exacerbated hypothalamic-pituitary adrenal responses to stress when exposed as neonates to anesthetic. Furthermore, recent studies suggest that these deleterious effects could be carried into the next generation via epigenetic mechanisms (noncoding RNAs, DNA methylation). There is a pressing need for further research, in order to establish safety guidelines for anesthesia in children, The authors of the present study exposed neonatal rats to sevoflurane and evaluated their progeny for inherited behavioral and molecular alterations.

Background We studied whether neonatal propofol anesthesia affects development of the endocrine and neural systems. Methods Sprague-Dawley rats were anesthetized using intraperitoneal propofol for 5 h on postnatal days (P) 4, 5, or 6. Pups that received either saline or intralipid, but not those in the negative control groups, were also maternally separated for 5 h. Serum levels of corticosterone were measured immediately after anesthesia and in adulthood after prepulse inhibition (PPI) of acoustic startle testing (≥P80), followed by measurement of hippocampal neuronal activity. Results Propofol acutely increased corticosterone levels to 146.6 ± 23.5 ng/ml (n=6) vs 16.4 ± 3.5 ng/ml (n=6) and 18.4 ± 3.2 ng/ml (n=6) in saline- and intralipd-treated pups, respectively. In adulthood, the propofol group exhibited exacerbated endocrine responses to stress in a form of increased corticosterone levels (1171.58 ± 149.17 ng/ml (n=15) vs 370.02 ± 36.01 ng/ml (n=10) in the saline group). The propofol group had increased the frequency of miniature inhibitory postsynaptic currents in CA1 neurons of male and female rats, but reduced PPI of startle was detected only in males. The Na+–K+–2Cl− co-transporter inhibitor bumetanide, administered to pups prior to propofol, alleviated long-term endocrine and PPI abnormalities. Exogenous corticosterone, administered to naïve pups, induced synaptic and endocrine, but not PPI effects, similar to those of propofol. Conclusions Propofol-caused acute increases in corticosterone levels and gamma-aminobutyric acid type A receptor-mediated excitation at the time of anesthesia may play mechanistic roles in development of exacerbated endocrine responses to stress and neurobehavioral abnormalities.