['Blockade of 5-hydroxytryptamine (5-HT)(2A) receptors reportedly mediates or modulates the ability of isoflurane to produce immobility during noxious stimulation and would thereby influence MAC (the minimum alveolar concentration required to suppress movement in response to noxious stimulation in 50% of subjects). However, no data are yet available regarding the role of this receptor in the immobilizing action of sevoflurane. In this study, we examined how prior intraperitoneal administration of either the 5-HT(2A) receptor antagonist altanserin or the 5-HT(2C/2B) receptor antagonist SB 206553 might affect sevoflurane MAC in rats.', 'Three groups of six male Wistar rats weighing 250-350\xa0g each received one of the following drugs dissolved in dimethyl sulfoxide intraperitoneally 30\xa0min before MAC testing: (1) altanserin 10\xa0mg/kg; (2) SB 206553 10\xa0mg/kg; (3) no drug (vehicle control). MAC was defined as the average of the concentrations that just prevented or just permitted movement in response to clamping the tail for 1\xa0min.', 'The rank order of MAC values obtained after intraperitoneal drug pretreatment and sevoflurane exposure was altanserin\xa0<\xa0SB 206553\xa0<\xa0vehicle control.'] Does blockade of 5-HT ( 2A ) and/or 5-HT ( 2C ) receptors modulate sevoflurane-induced immobility?