Pretreatment with reserpine to deplete catecholamines eliminates the ability of either timolol and WIN to reduce IOP. A, mean IOP recorded from each eye in C57BL6 mice pretreated with saline vehicle or reserpine to deplete catecholamines. B, mean IOP data for either vehicle or timolol treatment in mice pretreated with either saline (solid bars; n = 3), or reserpine (open bars; n = 5) to deplete catecholamines. *, p < 0.05 compared with the appropriate vehicle control. C, mean IOP data measured after topical application of either vehicle or WIN from mice pretreated with either saline (solid bars; n = 4) or reserpine (open bars; n = 6) to deplete catecholamines. **, p < 0.01 compared with the appropriate vehicle control.