The effect of sevoflurane on intracellular calcium concentration from cholinergic cells

The mechanism of action of volatile anesthetics is not completely understood. Calcium release from internal stores may alter signaling pathways that influence neurotransmission. Abnormalities of the regulation of intracellular calcium concentration ([Ca2+]i) from patients with malignant hyperthermia is a hallmark of this syndrome indicating the potential of these agents to interact with proteins involved in Ca2+ signaling. In the present study, a cholinergic cell line (SN56) was used to examine whether the release of calcium from intracellular stores occurs in the presence of sevoflurane. Changes in [Ca2+]i were measured using fluo-4, a fluorescent calcium sensitive dye and laser scanning confocal microscopy. Sevoflurane induced an increase on [Ca2+]i from SN56 cells. The sevoflurane-induced increase on [Ca2+]i remained even when the cells were perfused with medium lacking extracellular calcium. However, this effect was abolished by BAPTA-AM, a chelator of intracellular calcium, suggesting the involvement of intracellular Ca2+ stores. Using cyclopiazonic acid, an inhibitor of sarcoplasmic/endoplasmic reticulum Ca(2+)-ATPase, we investigated whether the depletion of intracellular Ca2+ stores interfered with the effect of sevoflurane. In the presence of this agent, sevoflurane caused a small but not significant rise on [Ca2+]i of the SN56 cells. Dantrolene, an inhibitor of ryanodine-sensitive calcium stores did not modify the sevoflurane increase on [Ca2+]i. Carbachol, a drug that releases Ca2+ from the IP3 pool, abolished the effect of sevoflurane. In addition, xestospongin D, a cell-permeant IP3 receptor antagonist, decreased significantly the sevoflurane increase on [Ca2+]i. Our data suggest that the sevoflurane-induced increase on [Ca2+]i from SN56 cells occurs through the release of calcium from IP3-sensitive calcium stores.