Previous work from this laboratory has demonstrated that hypoxia inhibits a TASK-1 like background K+ current in isolated neonatal rat carotid body type I cells. This inhibition leads to membrane depolarisation and voltage gated Ca2+ entry (Buckler, 1997; Buckler et al 2000). Maingret et al (2000) have demonstrated that the endocannabinoid anandamide was a direct and selective blocker of TASK-1. Therefore, in this study we have investigated the actions of anandamide and its analogue methanandamide on isolated type I cells.