Figure 6. Involvement of adenosine signaling in the endogenous osmotic volume regulation of retinal glial cells in mice. Adenosine, which is extracellularly formed from AMP by the action of CD73, activates A₁ receptors of Müller cells. Activation of the receptors triggers (via intracellular formation of cAMP) the opening of potassium and chloride channels in the Müller cell membrane. The ion efflux from the cells equalizes the osmotic gradient across the plasma membrane and thus prevents cellular swelling under hypotonic conditions. Different steps of the signaling cascade can be blocked by specific antagonists (shown in white), resulting in cellular swelling when the extracellular osmolarity decreases.