Effect of the general anaesthetics, alphaxalone, hexobarbitone and halothane on calcium uptake into rat brain mitochondria in vitro and in vivo.

In vitro studies of the effect of alphaxalone on ADP-stimulated respiration and Ca2+ uptake in rat brain mitochondria showed that the anesthetic was a potent inhibitor of both reactions. In vivo measurements showed that although alphaxalone did not inhibit oxidative phosphorylation during anaesthesia, the uptake of Ca2+ into the mitochondrial fraction was strongly inhibited. The degree of inhibition was dependent on the dose of anaesthetic administered and was reversed by the CNS stimulant, bemigride. Halothane and hexobarbitone also inhibited mitochondrial Ca2+ uptake in vivo. The levels of anaesthetic in the brain were determined after the administration of 14C-alphaxalone. There was no significant difference between the brain regions examined, but the levels reached were equal to those required to block CA2+ transport in isolated mitochondria.