The Estradiol Synthesis Inhibitor Formestane Diminishes the Ability of Sevoflurane to Induce Neurodevelopmental Abnormalities in Male Rats.

In rodents, the period of increased vulnerability to the developmental effects of general anesthetics coincides with the period of age-specific organizing (masculinizing) effects of the major female sex hormone 17β-estradiol (E2) in the male brain and excitatory GABA type A receptor (GABA A R) signaling. We studied whether E2 synthesis and excitatory GABA A R signaling are involved in the mediation of the developmental effects of sevoflurane in male rats. Male Sprague-Dawley rats were pretreated with the inhibitors of E2 synthesis, formestane, or the Na+-K+-2Cl- (NKCC1) Cl- importer, bumetanide, prior to sevoflurane exposure for 6 h on postnatal (P) day 4, P5, or P6. We tested whether a subsequent exposure of these rats to sevoflurane on P∼10 would cause electroencephalography (EEG)-detectable seizures. We also evaluated their behavior during the elevated plus maze (EPM) test on P∼60, prepulse inhibition (PPI) of acoustic startle responses on P∼70, and corticosterone secretion to physical restraint on P∼80. The rats neonatally exposed to sevoflurane responded to repeated exposure to sevoflurane with increased EEG-detectable seizures (F(3,24) = 7.445, P = 0.001) and exhibited deficiencies during the EPM (F(3,55) = 4.397, P = 0.008) and PPI (F(3,110) = 5.222, P = 0.003) tests. They also responded to physical restraint with heightened secretion of corticosterone (F(3,16) = 11.906, P < 0.001). These parameters in the sevoflurane-exposed rats that were pretreated with formestane or bumetanide were not different from those in the control rats. These results, along with previously published data, suggest that sevoflurane-enhanced E2 synthesis and excitatory GABA A R signaling at the time of sevoflurane anesthesia are involved in the mediation of the neurodevelopmental effects of the anesthetic in male rats.