Blood Pressure Reduction Induced by Low Dose of Epinephrine via Different Routes in Rats

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Abstract

Background:

Epinephrine was recently shown to induce a hypotension episode. Activation of β2-adrenoceptors with smooth muscle relaxation may be the underlying mechanism. This study investigated the effects of ICI 118551, a β2-adrenoceptors antagonist, on epinephrine-induced blood pressure reduction via different administration routes in rats.

Methods:

A total of 144 Sprague Dawley rats were equally randomized into 3 groups (intranasal, intravenous, and intra-arterial administration), each with 4 subgroups: saline + saline, ICI 118551 + saline, saline + epinephrine, and ICI 118551 + epinephrine. All rats were anesthetized while spontaneously breathing. Epinephrine was administered at doses of 5 μg/kg via nose, 0.25 μg/kg via femoral vein, and 0.1 μg/kg via aorta. Mean arterial pressure and heart rate were monitored.

Results:

Mean arterial pressure decreased in all 3 saline + epinephrine subgroups after administration (P < 0.05), whereas it did not in other subgroups. Heart rate had no significant change in all subgroups.

Conclusions:

Epinephrine-induced blood pressure reduction can be prevented by ICI 118551 in rats, suggesting that the activation of β2-adrenoceptors contributes to blood pressure reduction.

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