ISSN:
1432-1912
Keywords:
Key words Epinine (N-methyl-dopamine)
;
Dopamine
;
Prolactin
;
Dopaminergic receptors
;
Adrenergic receptors
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract Epinine (N-methyl-dopamine, the active metabolite of ibopamine), is a full agonist at dopamine (DA)-receptors and α- and β-adrenoceptors. To study whether in vivo DA-receptor mediated effects can be separated from α- and β-adrenoceptor effects we compared in 10 male volunteers the effects of i.v. epinine (0.5; 1; 2; 4 μg/kg/min for 15 min each) on DA-receptor (changes in serum prolactin)- and α- and β-adrenoceptor (changes in systolic [Psyst] and diastolic blood pressure [Pdiast] and heart rate)-mediated effects with those of dopamine before and after propranolol (5 mg i.v. 45 min pre-infusion), bisoprolol (15 mg p.o. 2 h pre-infusion) and domperidone (10 mg p.o. 1 h pre-infusion). At the 0.5 and 1 μg doses dopamine and epinine did not affect Psyst, Pdiast and heart rate but significantly decreased prolactin levels. At the higher dose both dopamine and epinine significantly increased Psyst and heart rate, while only epinine significantly increased Pdiast. In addition, both dopamine and epinine significantly increased diuresis and natriuresis; in contrast, only dopamine, but not epinine, dose-dependently increased plasma noradrenaline levels. Domperidone did not affect dopamine- and epinine-evoked blood pressure- and heart rate-changes, but antagonized their prolactin-effects (at least at the lower doses). Bisoprolol and propranolol significantly reduced dopamine-induced Psyst- and heart rate-increases to about the same extent. Propranolol enhanced epinine-induced Psyst- and Pdiast-increases while bisoprolol reduced epinine-evoked Psyst-increase but not Pdiast-increase. Epinine-induced heart rate-increase was abolished by biso-prolol and was converted into a heart rate-decrease by propranolol. We conclude that in 0.5 and 1 μg doses (plasma levels of 20–80 nmol/l) epinine acts only at DA-receptors. Thus, ibopamine in therapeutically recommended doses (3×100 mg/day with peak plasma epinine-levels of 50–80 nmol/l) very likely activates only DA-receptors. In higher doses, however, epinine - like dopamine - activates α- and β-adrenoceptors whereby epinine has a stronger α-adrenoceptor agonistic activity than dopamine. Moreover, part of the dopamine-effects are indirect via release of endogenous noradrenaline whereas epinine-effects do not appear to include an indirect component.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00172781
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