The extracellular adenosine concentration in the brain increases with metabolic load and signals through A1, A2A, A2B, and A3 receptors, but how individual subtypes regulate astrocytic energy metabolism remains incompletely defined. We combined live-cell FRET sensors for glucose, lactate, and cAMP with Ca²⁺ imaging in primary rat astrocytes to dissect receptor-specific actions. We also investigated mechano-metabolic coupling by applying brief pressure pulses and monitoring cytosolic lactate with the FRET-based Laconic nanosensor. We probed receptor contributions using adenosine and subtype selective agonists. Adenosine increased intracellular glucose concentration. Among subtypes, only A2B activation reproduced this effect. However, in glucose-free extracellular solution, adenosine and A2B activation elevated intracellular glucose, implicating glycogenolysis. PAS analysis showed that A2A and A2B increased perinuclear glycogen, with A2B also increasing peripheral glycogen. During recovery from glucose deprivation, adenosine and A2B receptor agonists slowed glycogen replenishment. cAMP concentration rose with A2A and A2B receptor stimulation and after A1 antagonism, but not with adenosine itself, consistent with balanced A1/A2 co-activation. Ca²⁺ responses were transient for adenosine/A1 and sustained for A2A/A2B. Selective A2B activation produced a significant increase in intracellular lactate compared with vehicle. Pressure pulses elicited pressure-dependent increases in cytosolic lactate. Together, these data identify A2B signalling as a principal driver of acute glucose mobilisation while slowing glycogen replenishment in astrocytes, operating through cAMP elevation and sustained Ca²⁺ signals, whereas A2A preferentially promotes perinuclear glycogen accumulation. Astrocytes convert brief mechanical stimuli into sustained metabolic signals.
|
