A retinal adrenergic module tunes mammalian visual evolution
How conserved neural circuits are modified during mammalian evolution remains poorly understood. Here we combine cross-species single-cell transcriptomics, in situ validation, retinal physiology, and conditional genetics to identify a superorder-associated adrenergic module in the mammalian retina. We find that ADRB1, which encodes the {beta}1-adrenergic receptor, is uniquely expressed in rod bipolar cells of sampled Euarchontoglires, but is absent from homologous cells in sampled Laurasiatheria and Marsupialia. In mice, {beta}1-adrenergic receptor localizes to rod bipolar cell terminals and boosts transmission to AII amacrine cells through Gs-adenylyl cyclase-cAMP-PKA signaling pathway. This modulation enhances synchronous release, accelerates downstream ganglion cell output, and increases scotopic electroretinographic responses, while rod-bipolar-cell-specific Adrb1 deletion abolishes norepinephrine-induced enhancement without disrupting baseline vision. In the diurnal tree shrew, a Euarchontoglires species with a cone-dominated retina, ADRB1 is instead redeployed from rod bipolar cells to cone photoreceptors. These findings reveal an evolutionarily mobile neuromodulatory module that tunes retinal computation according to visual ecology.