| Abstract: | The binding of [3H]dihydroalprenolol to beta-adrenergic receptors in the rat brainstem was studied. Propranolol inhibited dihydroalprenolol binding to a greater extent than did isoproterenol or epinephrine. Scatchard plots obtained with propranolol were biphasic whereas those obtained with isoproterenol and epinephrine were monophasic. The results indicate that in the brainstem propranolol displaces dihydroalprenolol from sites other than beta-adrenergic receptors. Nonspecific binding of dihydroalprenolol in this tissue therefore cannot be assayed using propranolol but should be measured with isoproterenol or epinephrine. |
