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  • Title: The mechanisms underlying heart stimulation by dopamine, with special reference to direct and indirect beta adrenoceptor stimulation.
    Author: Habuchi Y, Tanaka H, Yamamoto T, Komori T, Nishio M, Yoshimura M.
    Journal: Clin Exp Hypertens; 1997; 19(1-2):141-54. PubMed ID: 9028642.
    Abstract:
    1. The positive chronotropic and norepinephrine-releasing effects of dopamine were examined in the isolated guinea pig heart, using the Langendorff model. 2. The released norepinephrine was estimated from the norepinephrine concentration measured in the post-perfusion solution using HPLC. 3. The dose-response curve for dopamine to stimulate the heart rate (HR) closely resembled that for the norepinephrine release. A selective beta 1 antagonist bisoprolol completely abolished the positive chronotropic effect, but did not affect the norepinephrine release. 4. The HR increase in response to 3 mumol/L dopamine was 54 +/- 15% (n = 14) of the control in normal hearts. The response was decreased to 15 +/- 7% (n = 6) by pretreatment with reserpine. 5. A D1 antagonist, SKF83742, (3 mumol/L) shifted the dose-response curve for the dopamine-induced norepinephrine release toward the right, indicating the involvement of D1-like dopamine receptors. 6. Voltage clamp experiments using single cells isolated from the right atrium revealed that dopamine is a weak partial agonist for beta adrenoceptors. Dopamine stimulated the L-type Ca2+ current with a threshold concentration of 3 mumol/L. 7. These findings indicate the important role of the norepinephrine release in the stimulation of beta adrenoceptors by dopamine at clinically relevant concentrations.
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