Reduced inhibition of cortical glutamate and GABA release by halothane in mice lacking the K + channel, TREK‐1

Background and purpose: Deletion of TREK‐1, a two‐pore domain K + channel (K 2P ) activated by volatile anaesthetics, reduces volatile anaesthetic potency in mice, consistent with a role for TREK‐1 as an anaesthetic target. We used TREK‐1 knockout mice to examine the presynaptic function of TREK‐1 in transmitter release and its role in the selective inhibition of glutamate vs GABA release by volatile anaesthetics. Experimental approach: The effects of halothane on 4‐aminopyridine‐evoked and basal [ 3 H]glutamate and [ 14 C]GABA release from cerebrocortical nerve terminals isolated from TREK‐1 knockout (KO) and littermate wild‐type (WT) mice were compared. TREK‐1 was quantified by immunoblotting of nerve terminal preparations. Key results: Deletion of TREK‐1 significantly reduced the potency of halothane inhibition of 4‐aminopyridine‐evoked release of both glutamate and GABA without affecting control evoked release or the selective inhibition of glutamate vs GABA release. TREK‐1 deletion also reduced halothane inhibition of basal glutamate release, but did not affect basal GABA release. Conclusions and implications: The reduced sensitivity of glutamate and GABA release to inhibition by halothane in TREK‐1 KO nerve terminals correlates with the reduced anaesthetic potency of halothane in TREK‐1 KO mice observed in vivo . A presynaptic role for TREK‐1 was supported by the enrichment of TREK‐1 in isolated nerve terminals determined by immunoblotting. This study represents the first evidence for a link between an anaesthetic‐sensitive 2‐pore domain K + channel and presynaptic function, and provides further support for presynaptic mechanisms in determining volatile anaesthetic action. British Journal of Pharmacology (2007) 152 , 939–945; doi: 10.1038/sj.bjp.0707450 ; published online 10 September 2007