TASK-1 is a potassium channel that is constitutively leaky and thus helps maintaining the resting membrane potential. TASK-1 is not a classic cannabinoid receptor but its activity is modulated by cannabinoids. Since cannabinoids have a physiological effect on TASK-1 it is effectively a cannabinoid receptor.
http://www.guidetopharmacology.org/GRAC/ObjectDisplayForward?objectId=515
TASK-1 is coexpressed with TASK-3 in the cerebellar granule cells, locus coeruleus, motor neurons, pontine nuclei, some cells in the neocortex, habenula, olfactory bulb granule cells, and cells in the external plexiform layer of the olfactory bulb.
