AbstractThe potencies of the α‐adrenoceptor agonists clonidine, B‐HT 920 (2‐amino‐6‐allyl‐5,6,7,8‐tetrahydro‐4H‐thiazolo‐[5,4‐d]‐azepin), and B‐HT 933 (2‐amino‐6‐ethyl‐4,5,7,8,‐tetrahydro‐6H‐oxazolo‐[5,4‐d]‐azepin; Azepexole) in reversing reserpine‐induced ptosis in male NMRI mice were determined. Reserpine (2.5 mg/kg, i.p.) was administered 4 hr before intraperitoneal injection of the α‐adrenoceptor agonists. All three α‐adrenoceptor agonists produced dose‐dependent reversal of ptosis, this effect being maximal at about 15–30 min after injection. At 30 min postinjection, on a mg/kg basis, clonidine‐HCl was about 23 times more potent than B‐HT 920‐2 HCl and about 375 times more potent than B‐HT 933 2‐HCl in reversing ptosis. Although reversal of reserpine‐induced ptosis in the mouse is not selective for α2‐adrenoceptor agonists, these results indicate that this test can be used to compare the relative pote