ADRB2 and retinopathy of prematurity: Although several preclinical and trial studies focus on the administration of propranolol, a β1 and β2-AR β-blocker, during the hypoxic phase of the ROP [35], the finding that β3-ARs were particularly expressed in more aggressive and less responsive to propranolol cases sheds light on β3-ARs involvement in ROP pathogenesis [36].