title: Hypersensitivity of cardiac beta-adrenergic receptors after neonatal treatment of rats with 6-hydroxydopa.
abstract: The cardiac beta-adrenergic response to noradrenaline (NA) was investigated in the rat neonatally s.c. treated with 6-hydroxydopa (6-OHDOPA, 75 mg/kg, 0, 2 and 4 days after birth). 6-OHDOPA treatment significantly (P < 0.05) reduced the NA content by 32% of the control in whole heart and markedly potentiated the isoproterenol (0.17 mg/kg, i.p.)-induced stimulation of ornithine decarboxylase activity which had been blocked by a preceding i.p. injection of propranol (10 mg/kg) at the adult stage. Scatchard analysis of the specific [3H]-dihydroalprenolol ([3H]DHA0 binding indicated that 6-OHDOPA induced an increase in the maximum number of specific binding sites of [3H]DHA but did not alter the dissociation constant. In addition, 6-OHDOPA treatment resulted in a potentiation of the positive inotropic response to NA but not to isoproterenol in isolated atria. It is suggested that 6-OHDOPA treatment produces an increased density of beta-adrenergic receptor sites relevant to the hypersensitivity of beta-receptors to NA.
mesh_terms: D000818:Animals; D000831:Animals, Newborn / Q000378:metabolism; D001665:Binding Sites; D004082:Dihydroalprenolol / Q000378:metabolism; D004295:Dihydroxyphenylalanine / Q000031:analogs & derivatives* / Q000494:pharmacology; D005260:Female; D006321:Heart / Q000187:drug effects*; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects; D009206:Myocardium / Q000032:analysis / Q000378:metabolism; D009638:Norepinephrine / Q000494:pharmacology; D009955:Ornithine Decarboxylase / Q000032:analysis; D051381:Rats; D011941:Receptors, Adrenergic / Q000187:drug effects*; D011943:Receptors, Adrenergic, beta / Q000187:drug effects* / Q000502:physiology
chemical_list: D011941:Receptors, Adrenergic; D011943:Receptors, Adrenergic, beta; C001388:6-hydroxydopa; D004082:Dihydroalprenolol; D004295:Dihydroxyphenylalanine; D009955:Ornithine Decarboxylase; D007545:Isoproterenol; D009638:Norepinephrine