| Abstract: | The effects of propranolol, oxprenolol, pindolol, labetalol, and atenolol on the isoproterenol-stimulated slow calcium current as well as on spontaneous slow calcium and fast sodium currents were studied in frog trabeculae by the double sucrose bridge technique. Administration of beta-adrenoblockers in low doses (10(-7)-10(-6)M) antagonized the stimulatory effect of isoproterenol on the slow calcium current (pindolol greater than oxprenolol greater than or equal to propranolol = labetalol greater than atenolol). When administered in high doses (2 X 10(-6)-10(-4)M) the beta-adrenoblockers reduced the slow calcium current. Meanwhile, some of them (propranolol, oxprenolol, labetalol) suppressed the fast sodium current. |
