Anesthetic sevoflurane reduces levels of hippocalcin and postsynaptic density protein 95

Sevoflurane, the commonly used inhalation anesthetic in children, has been shown to enhance cytosolic calcium levels and induce cognitive impairment in young mice. However, the downstream consequences of the sevoflurane-induced elevation in cytosolic calcium levels and the upstream mechanisms of the sevoflurane-induced cognitive impairment remain largely to be determined. Hippocalcin is one of the neuronal calcium sensor proteins, and also binds to postsynaptic density protein 95 (PSD-95). We therefore set out to determine the effects of sevoflurane on the levels of hippocalcin and PSD-95 in vitro and in vivo. Hippocampus neurons from mice and 6-day-old mice were treated with 4.1% sevoflurane for 6 h or 3% sevoflurane 2 h daily for 3 days, respectively. We then measured the levels of hippocalcin and PSD-95, and assessed whether BAPTA, an intracellular calcium chelator, and memantine, a partial antagonist of the NMDA receptor, could inhibit the sevoflurane's effects. We found that sevoflurane decreased the levels of hippocalcin and PSD-95 in the neurons; and decreased the levels of hippocalcin and PSD-95 in the hippocampus of mice immediately after the anesthesia, but only the PSD-95 levels three weeks after the anesthesia. BAPTA inhibited the sevoflurane's effects in the neurons. Memantine attenuated the sevoflurane-induced reductions in the levels of hippocalcin and PSD-95, as well as the sevoflurane-induced cognitive impairment in mice. These data suggested that sevoflurane decreased the levels of hippocalcin and PSD-95, which could serve as one of bridge mechanisms between the sevoflurane-induced elevation of cytosolic calcium levels and the sevoflurane-induced cognitive impairment.