A GRAB sensor reveals activity-dependent non-vesicular somatodendritic adenosine release

Abstract

Abstract The purinergic signaling molecule adenosine (Ado) modulates many physiological and pathological brain functions,but its spatiotemporal release dynamics in the brain remains largely unknown. We developed a genetically encoded G PC R - A ctivation– B ased Ado sensor (GRAB Ado ) in which Ado-induced changes in the human A 2A receptor are reflected by fluorescence increases. This GRAB Ado revealed that neuronal activity-induced extracellular Ado elevation was due to direct Ado release from somatodendritic regions of the neuron, requiring calcium influx through L-type calcium channels, rather than the degradation of extracellular ATP. The Ado release was slow (∼30 s) and depended on equilibrative nucleoside transporters (ENTs) rather than conventional vesicular release mechanisms. Thus, GRAB Ado reveals an activity-dependent slow Ado release from somatodendritic region of the neuron, potentially serving modulating functions as a retrograde signal.