Effects of dopexamine hydrochloride on calcium channels in isolated guinea pig ventricular myocytes.
Methods Find Exp Clin Pharmacol
; 18(6): 353-7, 1996.
Article
in En
| MEDLINE
| ID: mdl-8892264
ABSTRACT
The mechanisms responsible for the cardiac positive inotropic effects of dopexamine hydrochloride, a combined dopamine receptor agonist at both D1-receptors and beta 2-adrenoceptors, were studied. The calcium channel currents were recorded using whole-cell patch clamp technique in isolated guinea pig ventricular myocytes. At a holding potential of -40 mV, cells were depolarized to 0 mV for 400 ms at a frequency of 0.2 Hz. Dopexamine hydrochloride at doses of 5, 50 and 100 microM increased the verapamil-sensitive Ca2+ inward current by 109, 147 and 194%, respectively. The effects of dopexamine hydrochloride on Ca2+ current reached its maximum at 5 min and partially recovered after washout of the drugs. The increased Ca2+ current induced by dopexamine hydrochloride was completely inhibited by 20 microM propranolol, a beta-adrenoceptor antagonist, and was not antagonized by 20 microM of SCH23390, a highly selective D1-receptor antagonist. These results suggest that the cardiac positive inotropic effects of dopexamine hydrochloride are brought about by the increase of Ca2+ current via stimulation of beta 2-adrenoceptors.
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Collection:
01-internacional
Database:
MEDLINE
Main subject:
Calcium Channels
/
Dopamine
/
Adrenergic beta-Agonists
/
Dopamine Agonists
/
Heart Ventricles
/
Myocardium
Limits:
Animals
Language:
En
Journal:
Methods Find Exp Clin Pharmacol
Year:
1996
Type:
Article
Affiliation country:
China